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GREAT FACTS.


[Illustration: THE "GREAT EASTERN" STEAMSHIP, LAUNCHED 1858.]




  GREAT FACTS:

  A
  POPULAR HISTORY AND DESCRIPTION
  OF THE MOST
  REMARKABLE INVENTIONS
  DURING THE PRESENT CENTURY.


  BY
  FREDERICK C. BAKEWELL,
  AUTHOR OF
  "PHILOSOPHICAL CONVERSATIONS," "MANUAL OF ELECTRICITY," ETC.
  ILLUSTRATED WITH NUMEROUS ENGRAVINGS.


  NEW YORK:
  D. APPLETON AND COMPANY,
  346 & 348 BROADWAY.
  1860.




PREFACE.


The conveniences, the comforts, and luxuries conferred on Society by
the many important Inventions of the present century, must naturally
excite a desire to know the origin and progress of the application of
scientific principles, by which such advantages have been gained.

Practically considered, those Inventions are of much greater value
than the discoveries of Science on which most of them depend; and the
scientific inquirer who confines his views to abstract principles,
without looking beyond them to the varied methods of their application
to useful purposes, may be compared to a traveller who, having toiled
arduously to gain the top of a mountain, then shuts his eyes on the
prospect that lies before him.

To the inquiring youth, more particularly, it is desirable that he
should be enabled to satisfy his wish to know by what means such
wonders as Steam Navigation, Locomotion on Railways, the Electric
Telegraph, and Photography have been gradually developed; and in
becoming acquainted with the successive steps by which they have
advanced towards their present perfection, he will at the same time
learn a useful lesson of perseverance under difficulties, and will have
his mind impressed with many valuable scientific truths. The knowledge
to be gained by such inquiry is eminently practical, and of a kind
which those engaged in any of the pursuits of life can scarcely fail to
require.

A History of Inventions almost necessarily implies a description of
the mechanisms and processes by which they are effected; so far, at
least, as to render the principles on which their actions depend
understood. It would be impossible, however, in a work of this limited
size to enter minutely into explanations of mechanisms, and into the
applications of scientific discoveries, which would require a separate
treatise for each; but it has been the Author's endeavour to give a
succinct, intelligible account, free from technicalities, of the manner
in which they operate, so as to be comprehensible to all classes of
readers.

By thus giving a popular character to the work, to make it acceptable
to the young, it is hoped that it will not be found less worthy, on
that account, the perusal of those more advanced in life.

When Beckman wrote his History of Inventions, towards the close
of last century, scarcely any of the wonderful discoveries and
contrivances that now form parts of our social system were known;
and the table of contents of his two large volumes affords a curious
insight to the nature and limited extent of such contrivances as were
then considered most important. The introduction into his history
of such subjects as canary birds, carp, the adulteration of wine,
apothecaries, cock-fighting, and juggling, lead us to infer that the
Historian of Inventions at that time must have had some difficulty to
find appropriate matter wherewith to fill his volumes. The opposite
difficulty now presents itself. The numerous important, wonderful,
and curious accomplishments of human skill and ingenuity during the
present century render preference perplexing, where so many deserve
description. From among the number that press for notice, the Author
has endeavoured to select those that are either the most important, the
most remarkable, or that seem to possess the germs of future progress;
and he trusts that the selection he has made, and the mode in which the
subjects have been treated, will render this volume interesting and
instructive.

        F. C. B.

  _6 Haverstock Terrace, Hampstead,
      November, 1858._




CONTENTS.


                                                              PAGE
  THE PROGRESS OF INVENTION                                      1
  STEAM NAVIGATION                                               6
  STEAM CARRIAGES AND RAILWAYS                                  32
  THE AIR ENGINE                                                60
  PHOTOGRAPHY                                                   67
  DISSOLVING VIEWS                                              86
  THE KALEIDOSCOPE                                              92
  THE MAGIC DISC                                                98
  THE DIORAMA                                                  103
  THE STEREOSCOPE                                              112
  THE ELECTRIC TELEGRAPH                                       124
  ELECTRO-MAGNETIC CLOCKS                                      172
  ELECTRO-METALLURGY                                           179
  GAS LIGHTING                                                 188
  THE ELECTRIC LIGHT                                           209
  INSTANTANEOUS LIGHTS                                         214
  PAPER MAKING MACHINERY                                       221
  PRINTING MACHINES                                            230
  LITHOGRAPHY                                                  249
  AERATED WATERS                                               258
  REVOLVERS AND MINIÉ RIFLES                                   266
  CENTRIFUGAL PUMPS                                            275
  TUBULAR BRIDGES                                              282
  SELF-ACTING ENGINES, INCLUDING THE NASMYTH STEAM HAMMER      295




GREAT FACTS.




THE PROGRESS OF INVENTION.


The inventive faculty of man tends more directly than any other
intellectual power he possesses to raise him in the scale of creation
above the brutes. Nearly every advance he makes beyond the exercise of
his natural instincts is caused by invention--by that power of the mind
which combines known properties in different ways to obtain new results.

When an Indian clothes himself with the skins of animals, and when
he collects the dried leaves of the forest for his bed, he is either
an original inventor, or he is profiting by the inventions of
others. Those simple contrivances--the first steps in the progress
of invention--are succeeded by the more labored efforts of inventive
genius, such as contriving means of shelter from rain, or from
the heat of the sun, when caves cannot be found to creep into, or
the overhanging foliage fails to afford sufficient covering. The
construction of places of shelter is an imitation of the protection
formed by Nature; and the rudest hut and the most magnificent palaces
have their prototypes in caverns and in the interlacing branches of
trees.

Nature also supplies knowledge of the means by which inventors are
enabled to work. The savage who seizes hold of a broken bough is
in possession of the _lever_, the uses of which he learns by the
facility it affords in moving other objects. He ascends to the top of
a precipice by walking up the sloping hill behind, and he thus becomes
practically acquainted with the principle of the _inclined plane_.
The elements of all the mechanical powers are then at his command, to
be applied by degrees in administering to his wants, as his inventive
faculties, guided by observation and experience, suggest. An accidental
kick against a loose stone shows the action of propulsive force; and
the stone that he has struck with his foot, he learns to throw with his
hand. The bending of the boughs of trees to and fro by the wind teaches
the action of springs; and in the course of time the bow is bent by a
strip of hide, and the relaxation of the spring, after farther bending,
propels the arrow. Observation and imitation thus lead to invention,
and every new invention forms the foundation of further progress.

It has been so with every invention at present known, and must so
continue to the end of time:--"There is nothing new under the sun." Gas
lighting, Steam locomotion, and the Electric Telegraph have each sprung
from some source "old as the hills," though so modified by gradually
progressive changes, that the giant we now see bears no resemblance to
the infant of ages past.

The observation that light particles floating in the air are attracted
by amber when rubbed, which was made known six centuries before the
Christian era, was the origin of the invention by which communications
are now transmitted, with the rapidity of lightning, from one part of
the world to another. There is no apparent relation between effects
so dissimilar; yet the steps of progress can be distinctly traced,
from the attraction of a feather to the development of the electric
telegraph.

Whenever the history of an invention can be thus tracked backward to
its source, it will be found to have advanced to its present state by
progressive steps, each additional advance having been dependent on
the help given by the progress before made. Sometimes these onward
movements are greater and more remarkable than others, and the persons
who made them have become distinguished for their inventive genius,
and are considered the benefactors of mankind; yet they were but the
followers of those who had gone before and shown the way.

Many of the most remarkable inventions are attributable to accidents
noted by observing and inventive minds. Not unfrequently also have
important discoveries of truth been made in endeavouring to establish
error; and new light is being constantly thrown on the path of
invention by unsuccessful experiments.

This view of the means by which inventions originate and are brought
to perfection may appear to detract from the merit of inventors, since
it regards them as founding their conceptions altogether on the works
of others, or on chance. But instead of diminishing their claims to
approbation and reward, it places those claims on a more substantial
foundation than that of abstract original ideas. The man who has the
faculty to perceive that by a different application of well-known
principles he can produce useful effects before unknown, directly
benefits mankind far more than the discoverer of the principles which
had till then lain dormant; and the numerous difficulties which ever
arise before an invention can be practically operative, frequently
afford exercise for reasoning powers of the highest kind, which may
develop new arrangements, that exhibit as much originality and research
as were displayed by the discoverers of the principles on which the
invention depends.

The dependence of every invention on preceding ones produces very
frequently conflicting claims among inventors, who, forgetting how
much they were indebted to others, do not hesitate to charge those,
who make still further improvements, with imitation and piracy. It is,
indeed, sometimes difficult to determine whether the alterations made
in well-known contrivances are, or are not, of sufficient importance
to constitute inventions; and there can be no doubt that there is too
great facility afforded, by the indiscriminate grant of letters patent,
for the establishment of monopolies that often serve to obstruct
further improvements. At the same time, it must be observed that a
very trifling addition or change occasionally gives practical value to
an invention, which had been useless without it. In such cases, though
the individual merit of the inventor is small, the benefit conferred
may be important, and may operate influentially in promoting the
progress of civilization.

Scientific discovery goes hand in hand with invention, and they
mutually assist each other's progress. Every discovery in science
may be applicable to some new purpose, or give greater efficiency to
what is old. Those new and improved instruments and processes provide
science with the means of extending its researches into other fields of
discovery; and thus, as every truth revealed, supplies inventive genius
with fresh matter to mould into new forms, those creations become in
their turn agents in promoting further discoveries.

The action and reaction thus constantly at work, tend to give
accelerating impulse to invention, and are continually enlarging its
sphere of operations. Instead, therefore, of supposing, as some do,
that invention and discovery have nearly reached their limits, there is
more reason to infer that they are only at the commencement of their
careers; and that, great as have been the wonders accomplished by the
applications of science during the first half of the present century,
they will be at least equalled, if not surpassed, by those to be
achieved before its close.




STEAM NAVIGATION.


Ships, propelled by some mysterious power against wind and against
tide, cutting their ways through the water without apparent impulse
and like things of life, were not unfrequently seen gliding along in
the regions of fancy, ages before the realization of such objects on
geographical seas and rivers was looked upon as in the slightest degree
possible. Even at the beginning of the present century, it seemed to
be more probable that man would be able to navigate the air at will,
than that he should be able, without wind or current, and in opposition
to both, to propel and steer large ships over the waves; yet, within
twenty years afterwards, Steam Navigation had ceased to be a wonder.

If we look back into the records of past ages, we find that inventive
genius was active in the earliest times, in endeavouring to find other
means of propelling boats than by manual labour and the uncertain wind,
some of which contrivances point to the method subsequently adopted by
the constructors of steam-vessels.

To enable us to appreciate properly the gradual advances that have
been made in perfecting any invention, it is necessary to consider its
distinguishing features, and the difficulties which inventors have had
successively to contend against. On taking this view of the progress
of Steam Navigation, it will be found that the amount of novelty to
which each inventor has a claim is very small, and that his principal
merit consists in the application of other inventions to accomplish
his special object. The same remark will indeed apply to most other
inventions; for the utmost that inventive genius can accomplish, is to
put together in new forms, and with different applications, preceding
contrivances and discoveries, which were also the results of antecedent
knowledge, labour, and skill.

When, for instance, we look upon an ordinary steam-boat, the most
remarkable and the most important feature is the paddle-wheel, by the
action of which against the water the boat is propelled. Yet that
method of propelling boats was practised by the Egyptians hundreds of
years before steam power was thought of; and the ancient Romans made
use of similar wheels, worked by hand, as substitutes for oars. It
would seem, therefore, to be only a small step in inventive progress,
after the discovery of the steam engine, to apply that motive power to
turn the paddle-wheels which had been previously used; and now that we
see the perfected invention, it may surprise those who are unacquainted
with the difficulties which attend any new appliance, that Steam
Navigation did not sooner become an accomplished fact.

In a book called "Inventions and Devices," by William Bourne, published
in 1578, it was proposed to make a boat go by paddle-wheels, "to be
turned by some provision." The Marquis of Worcester, in his "Century
of Inventions," also speaks vaguely of a mode of propelling ships. But
Capt. Savery, the inventor of the earliest working steam engine, was
the first to suggest the application of steam to navigation; and Dr.
Papin, who contended with Savery for priority of the invention, also
suggested about the same time the application of the elastic force of
steam to that purpose.

These crude notions, however, do not deserve to be considered as
inventions, though they probably assisted in suggesting the idea of
the plan proposed by Mr. Jonathan Hulls, who in 1736 took out a patent
for a steam-boat, and in the following year published a description of
his invention, illustrated by a drawing, entitled, "A description and
draught of a new-invented machine for carrying vessels or ships out
of or into any harbour, port, or river, against wind or tide, or in a
calm."

The greater part of this publication is occupied with answers to
objections that he supposed might be raised to the scheme, and in the
preface he makes the following observations on the treatment inventors
were exposed to in his day, which we fear will apply equally at the
present time. "There is," he says, "one great hardship lies too
commonly on those who purpose to advance some new though useful scheme
for the public benefit. The world abounding more in rash censure than
in candid and unprejudiced estimation of things, if a person does not
answer their expectations in every point, instead of friendly treatment
for his good intentions, he too often meets with ridicule and contempt."

[Illustration]

At the time of Mr. Hulls' invention, Watt had not made his improvements
in the steam engine, and the kind of engine Hulls employed was similar
to Newcomen's, in which the steam was condensed in the cylinder,
and the piston, after being forced down by the direct pressure of
the atmosphere, was drawn upwards again by a weight. The paddle, or
"vanes," as he called them, were placed at the stern, between two
wheels, which were turned by ropes passing over their peripheries.
The alternate motion of the piston was ingeniously converted into a
continuous rotary movement, by connection with other ropes attached to
the piston and to the weight, the backward movement being prevented by
a catch or click.

The woodcut which lays before you is a reduced copy of Hulls'
"draught" of his steam-boat, as given in his book, a copy of which is
preserved in the British Museum.

The utmost application of steam power to navigation contemplated by
Hulls was to tow large vessels into or out of harbour, in calm weather,
by means of a separate steam tug-boat, as he considered the cumbersome
mechanism would be found objectionable on board the ships to be thus
propelled. It does not appear that this plan was effectually tried,
nor was the arrangement of the mechanism, nor the imperfect condition
of the steam engine at that period, calculated to make the effort
successful.

For some years after Mr. Hulls' plan had been published, and had
proved abortive, no further attempt seems to have been made, until the
improvements in the steam engine, by Watt, rendered it more applicable
for the purpose of navigation. The French claim for the Marquis de
Jouffroy the honour of having been the first who successfully applied
steam power to propel boats, in 1782; though another French nobleman,
the Comte d'Auxiron, and M. Perier, had eight years previously made
some experiments with steam-boats on the Seine. The Marquis de
Jouffroy's steam-boat, which was 145 feet long, was tried on the Soane,
near Lyons, with good promise of success. The marquis was, however,
obliged to leave France by the fury of the Revolution, and when he
returned in 1796, he found that a patent had been granted to M. le
Blanc, for building steam-boats in France. He protested against the
monopoly, but the patent remained in force, and the plan received
no further development, either from the Marquis de Jouffroy, or the
patentee.

About five years later, Mr. Patrick Miller, of Dalswinton, in Scotland,
directed his attention to the propulsion of boats by mechanical means,
and contrived different kinds of paddles, and other propellers to be
worked by hand, which were tried on boats on Dalswinton Lake. The
great labour required to work these machines induced Mr. James Taylor,
a tutor in Mr. Miller's family, to suggest the use of steam power to
turn them, and he recommended Mr. Miller to obtain the assistance of
William Symington, an engineer, who was at that time endeavouring to
make a steam locomotive carriage. Among the first difficulties that
suggested themselves, was the danger of setting fire to the boat by
the engine furnace. This difficulty was overcome by Mr. Taylor, and
the arrangements were completed, and the experiment was tried in 1788.
The steam engine and mechanism were applied to a double pleasure-boat;
the engine being placed on one side, the boiler on the other, and the
paddle-wheel in the centre. The cylinders of the steam engine were only
four inches in diameter; but with this engine the boat was propelled
across Dalswinton Lake at a speed of five miles an hour.

The success of this experiment induced Mr. Miller to have a larger
boat built, expressly adapted for the introduction of a steam engine.
It was constructed under the superintendence of Symington, and was
tried successfully on the Forth and Clyde Canal in 1789, when it was
propelled at the rate of seven miles an hour.

In the arrangement of the mechanism of this boat, the cylinder was
placed horizontally, for the purpose of making connection between the
paddle-wheel and the piston, without the working beam. The piston was
supported in its position by friction wheels, and communicated motion
to the paddles by a crank. The paddles were placed in the middle of the
boat, near the stern; and there was a double rudder, connected together
by rods which were moved by a winch at the head of the vessel.

It is not very clear why Mr. Miller did not follow up this success.
Objection, indeed, was made by the proprietors of the canal on account
of the agitation of the water, which it was feared would injure
the banks. It would appear also that a misunderstanding took place
between Miller and Symington, which gave the former a distaste to the
undertaking; and having shown that such a plan was practicable, he left
others to carry it into practical effect.

Several methods of propelling boats, otherwise than by paddles, had
some years previously been suggested; among which were two that have
been again and again tried by succeeding inventors, down to the present
day.

One of these is an imitation of the duck's foot, which expands when it
strikes the water, and collapses when it is withdrawn. The other is
the ejection of a stream of water at the stern, or on both sides of
the boat, so as to produce a forward movement by reaction. Both these
plans of propulsion seem feasible in design; but they have hitherto
failed in practice. A pastor at Berne, named J. A. Genevois, has the
credit of having invented the duck-feet propeller in 1755; and in 1795,
six years after Mr. Miller's successful experiments, Earl Stanhope had
a steam-boat built on that principle. It was so far a failure, that it
was not propelled faster than three miles an hour. The other method of
propulsion, though of older date, was patented in 1800 by Mr. Linnaker,
who proposed to draw the water in at the head of the vessel, and eject
it at the stern, and thus to obtain a double action on the water for
propelling; but the plan was not found to answer.

In 1801, Lord Dundas revived Mr. Miller's project, and availed himself
of Mr. Symington's increased experience and the further improvements in
the steam engine, to construct a much more perfect steam-boat than any
that had been made. He spent £3,000 in the experiments, and in March,
1802, his vessel, called the "Charlotte Dundas," was tried on the same
scene of action, the Forth and Clyde Canal. This boat, according to
Symington's report, towed two vessels, each of seventy tons burthen, a
distance of nineteen miles and a half in six hours, against a strong
wind. The threatened injury to the banks of the canal by the great
agitation of the water prevented the use of this boat, which was
consequently laid aside; for the views of the inventors of steam-boats
in the first instance were limited to their employment to drag boats
along canals.

We now approach a period when more decided advances and more rapid
progress were made towards realizing steam navigation as a practical
fact. Mr. Fulton, an American, residing in France, after making a
number of experiments, under the sanction and with the assistance of
Mr. Livingstone, the American Ambassador, launched a small steam-boat
on the Seine in 1803, but the weight of the engine proved too great for
the strength of the boat, which broke in the middle, and immediately
went to the bottom.

Not disheartened by this failure he built another one, longer and
stronger, and this he succeeded in propelling by steam power, though
very slowly. It was, indeed, a much less successful effort than the
attempts of Mr. Miller and Lord Dundas. Having been threatened with
opposition by M. le Blanc, the patentee of steam-boats in France,
Fulton determined to return to his native country, where the large
navigable rivers and lakes offered ample scope for the development of
steam navigation. Having heard of the success of Symington's boats,
he visited Scotland for the purpose of profiting by his experience;
and he induced Symington, by promises of great advantages if the
invention succeeded in America, to show him the "Charlotte Dundas" at
work, and to enter into full explanations of every part. Thus primed
with the facts, and with the further suggestions of Symington, Fulton
repaired to New York. Mr. Livingstone, who had assisted Fulton in his
experiments, was himself an inventor of several plans of propelling
vessels by steam, and in 1798 he obtained a patent in the State of
New York, for twenty years, on condition that he should produce a
steam-boat by the 7th of March, 1799, that would go at the rate of
_four_ miles an hour. Having failed to fulfil that condition, the
patent privilege was left open, and was promised to the first inventor
who succeeded in propelling a boat by steam power at the proposed
speed of four miles an hour. Fulton, who had entered into partnership
with Mr. Livingstone, possessed advantages in the construction of the
vessel he built in America, far greater than any previous inventor. He
had not only gained knowledge by his former failures, but he was able
to profit by the experience of others, and he had secured a superior
steam engine, manufactured by Boulton and Watt, of twenty-horse power.
This was a much more powerful engine than any that had been used in
any former experiment; the one employed by Mr. Livingstone having had
only five-horse power. This steam-vessel was launched at New York in
1807, and was called the "Clermont," the name of Mr. Livingstone's
residence on the banks of the Hudson. Its length was 133 feet, depth 7
feet, and breadth 18 feet. The boiler was 20 feet long, 7 feet deep,
and 8 feet broad. There was only one steam cylinder, which was 2 feet
in diameter, with a length of stroke of 4 feet. The paddle-wheels were
15 feet in diameter, and 5 feet broad; and the burthen of the vessel
was 160 tons. Crowds of spectators assembled to see the boat start on
its first experimental voyage. The general impression, even of those
who were friendly to Fulton, was that it would fail, and an accident
which occurred when the vessel was under way confirmed this opinion.
The foreboders of evil exclaimed immediately that they had "foreseen
something of the kind;" and observed "it was a pity so much expense
had been incurred for nothing!" The required repairs were, however,
soon made. The vessel when again tried cut her way bravely through
the water, to the astonishment of all, and the doubts, and fears, and
lamentations were quickly changed into congratulations.

As the "Clermont" urged its way up the Hudson, its chimney emitting
innumerable sparks from the dried pine wood used as fuel, it excited
great alarm among those who were not prepared for such an apparition.
An American paper of that day thus described the effect produced on
the crews of other ships in the river:--"Notwithstanding the wind and
tide were adverse to its approach, they saw with astonishment that
it was rapidly coming towards them; and when it came so near that
the noise of the machinery and paddles was heard, the crews, in some
instances, shrunk beneath their decks from the terrific sight, or left
their vessels to go on shore; whilst others prostrated themselves and
besought Providence to protect them from the approach of the horrible
monster which was marching on the waves, and lighting its path by the
fires which it vomited."

During the time that Fulton was building his steam-boat Mr. R. L.
Stevens, of Hoboken, in the State of New Jersey, was also engaged in a
similar undertaking. Though his name is comparatively little heard of
in the history of Steam Navigation, his efforts were more successful
than any that had been made previously, and but for the fortunate
chance to Fulton that he was able to launch and put his boat in action
a few days before Stevens had completed his, all, and more than all,
the merit that is now ascribed to the former would have been attributed
to Stevens. The previous successful experiment of Fulton having
fulfilled the conditions imposed by the State of New York, he obtained
the exclusive right of steam navigation on the rivers and along the
coast of that State; therefore, after Stevens had launched his boat on
the Hudson, he was unable to employ it there. In this predicament he
ventured on the hazardous experiment of taking his steam-vessel by sea,
and successfully accomplished his voyage from New York to Delaware.
This was the first attempt to put to sea in a steam-boat.

Mr. Stevens introduced many important improvements. He increased the
length of stroke of the engines; he applied upright guides for the
piston-rod, to supply the place of the parallel motion; and he divided
the paddle-wheel by boards, by which means a more uniform motion was
obtained. By these improvements he succeeded in raising the speed of
steam-vessels to thirteen miles an hour.

Whilst Steam Navigation was making such progress in America, it was not
neglected in this country. Mr. Henry Bell, of Glasgow, a man of great
ingenuity, had for some time directed his attention to the subject,
and had given some useful hints to Fulton. Seeing, as he afterwards
said, no reason why others should profit by his plans without his
participation in the fame and the profits, he determined to build a
steam-boat himself, which was completed and launched in 1811. Bell
called his boat the "Comet," in commemoration of the remarkable
eccentric luminary which was at that time frightening Europe from
its propriety. The boat was 25 tons burthen, with an engine of about
3-horse power. It plied on the Frith of Forth for a distance of 27
miles, which in ordinary weather it accomplished in 3½ hours. The
"Comet" is generally supposed to have been the first steam-boat that
plied regularly in Europe; and its construction was so perfect, that
no boat built for many years afterwards surpassed it, taking into
consideration its size and the small power of its engine. Bell, though
he had done so much to advance Steam Navigation in this country, was
allowed to suffer neglect and penury in his old age, till the town of
Glasgow granted him a small annuity for his services.

A claim has been preferred on behalf of Messrs. Furnace and Ashton, of
Hull, to priority in building the first steam-vessel that was worked
in England. It is stated, that "about the year 1787, experiments were
made on the river Hull, by Furnace and Ashton, on the propulsion
of vessels by steam power. Furnace and Ashton built a boat, which
plied on the river, between Hull and Beverley, for some time, and
answered exceedingly well. In consequence of the good results of their
experiments, they built a much larger vessel and engine, and sent the
whole to London, to be put together and finished; after which it was
subjected to the severest tests, and gave the greatest satisfaction.
The vessel was bought by the Prince Regent (afterwards George IV.),
who had it fitted and furnished as a pleasure yacht; but it was soon
afterwards burnt, having, it is supposed, been wilfully set on fire
by persons who were afraid that such an invention would be injurious
to their calling. The Prince was so much pleased with the invention
and ingenuity of Furnace and Ashton, that he granted them a pension
for their lives of £70 a year each."[1] This steamer was on the
paddle-wheel principle, propelled by a steam engine, to which was
attached a copper boiler.

From this time forward the progress of Steam Navigation was very
rapid. Steam-ships were built longer and larger, and with more
powerful engines; and the most skilful builders rivalled each other
in the construction and adaptation of their vessels and engines, so
as to attain the highest possible speed. The locality in which Steam
Navigation may be said to have had its birth continued for a long time
to be pre-eminent, and steam-boats built on the Clyde still rank very
high, if not the highest, in the scale of excellence.

The ordinary land steam engine required considerable alterations to
adapt it to marine purposes; nor was it till great experience had been
gained in propelling vessels by steam power, that the more essentially
requisite modifications were adopted. It was found important, in the
first place, to reduce the space occupied by the machinery as much as
possible. The boilers were consequently made of less dimensions, but
more extensive in their heating surface. It was also found desirable
to employ two engines instead of one, the pistons being made to rise
and descend alternately. By this means the motion was rendered more
equable, and by placing the cranks of the common shaft at right angles,
the "dead points" were passed more readily, and the want of a fly wheel
was thus compensated.

The steam-boats employed in this country were, almost from the first,
and continue with few exceptions to be, on the low-pressure condensing
principle; the whole of the machinery being placed below the deck. This
renders it necessary to diminish the height of the engines as much
as possible; and in all marine steam engines, till within the last
twenty years, instead of having a working beam over the cylinders,
a cross-head was placed at the top of the piston-rod, the action of
which was conveyed by parallel motions to cross beams on each side,
which were situated at the bottom part of each engine. The motion,
compared with that of an ordinary land engine, was thus inverted. The
proportions of the cylinders were also different; the length of stroke
being shorter, to diminish the height, and the diameter consequently
greater. The valves, and the gearing connected with them, the air pump,
the condenser, and other subsidiary parts, do not differ essentially
from those of land engines; but the governor is omitted, as it is found
impracticable to work a marine engine with great regularity.

Latterly, many engineers have introduced, with much success,
arrangements for communicating the action directly from the piston-rod
to the crank, without the intervention of the beam and parallel
motions. This is generally done by causing the piston-rod to work
between guides, and a jointed arm connects it with the crank. One
method of producing the same effect is to make the cylinders oscillate
on pivots, as contrived by Mr. Murdoch, in the first model steam
carriage, made in 1784. This principle has been successfully carried
into operation by Messrs. Penn, of Greenwich. The oscillating cylinders
accommodate themselves to the varying directions of the cranks, and
the strain occasioned by guide rods is diminished; but when very large
cylinders are required, the friction and the pressure on the pivots
must tend to counterbalance the advantage otherwise obtained.

In the ordinary paddle-wheel steam-boats, the floats of the
paddle-wheels are fixed at equal distances round the rim, radiating
from the centre; therefore they enter and come out of the water
obliquely. There is, consequently, a considerable loss of power
attending the use of such paddle-wheels, as only one float at a time
can be acting vertically on the water, and exerting the propelling
force in a direct line. Several attempts have been made to remedy this
defect, and to produce what is called "feathering" floats, every one
of which will act against the water at right angles. The mechanism
required for making this adjustment is, however, liable to get out
of order, and the introduction of vertically acting floats has
consequently been very limited.

The large projecting paddle-boxes are objectionable in sea-going
ships, as they present so large a surface to the action of the wind,
and either impede the course of the ship, or make it unweatherly.
This inconvenience was experienced in the early progress of Steam
Navigation, and many attempts were made to overcome it, by substituting
a different kind of propeller. Recourse was had to the inventions of
the ancients, from whom the paddle-wheel was taken, to find some other
means of propulsion. A method of propulsion, similar in principle to
the action of sculls at the back of a boat, had been contrived long
before the inconvenience of paddle-wheels in Steam Navigation was
experienced. In 1784, Mr. Bramah obtained a patent for a propeller
similar in its forms to the vanes of a windmill, which by acting
obliquely on the water as it revolved, pushed the boat forward. Ten
years afterwards, an "aquatic propeller" was patented by Mr. William
Lyttleton, a merchant in London. It consisted of a single convolution
of a three-threaded screw, and may be considered to be the first screw
propeller invented. Numerous other ingenious persons, among whom were
Tredgold, Trevethick, Maceroni, and Millington, afterwards invented
propellers on the screw principle; but none of them were sufficiently
satisfactory in their results to come into practical use.

In 1836, Mr. Smith and Mr. Ericsson obtained a patent for a screw
propeller, which nearly resembled Mr. Lyttleton's original contrivance;
and by perseverance in struggling against the many obstacles with
which he had to contend, Mr. Smith succeeded, though all previous
efforts had failed. His partner, however, became disheartened by the
obstacles thrown in their way, and left this country for America before
the success of the screw was established.

The first ship fitted with the screw propeller was called the
"Archimedes." It was a vessel of 237 tons burthen, with a draught of
water of 9 feet 4 inches. The screw projected at the stern, and being
turned rapidly round by the steam engine, the oblique action of the
thread of the screw against the water impelled the vessel forward.

The "Archimedes" was originally fitted with a single-threaded screw,
the threads of which were 8 feet apart, and there were two convolutions
of the screw round the shaft. One convolution of the screw having
been accidentally broken off, the ship was found to go faster in
consequence; and, following the course of investigation suggested by
the accident, Mr. Smith at last adopted a double-threaded screw, with
only half a convolution. The average performance of the engines was 26
strokes per minute, and the number of revolutions of the screw in the
same time was 138½. The "pitch" of the screw was 8 feet; that is, the
space across one entire convolution of the thread would have measured
8 feet; consequently, had it been acting against a solid body, as a
cork-screw when entering a cork, one revolution of the shaft would have
advanced the vessel 8 feet, and the speed would have been 12½ miles an
hour; but the utmost speed the "Archimedes" obtained was 9¼ nautical
miles. The difference was owing to the screw "slipping" in the water,
because the fluid yielded to the oblique action of the blades.

[Illustration]

The results of the working of that experimental ship were so
satisfactory, that other ships were soon built, with modifications
of the form of the propeller. It was found disadvantageous to have
an entire convolution of the thread of the screw; for one part of it
worked in the wake of the other, and resistance was produced by the
backwater. After numerous experiments, in which the dimensions of the
screw were successively diminished, the propeller was at length reduced
to two oblique blades. Experiments on a large scale were conducted by
Captain Carpenter, to determine the size and angle of inclination best
adapted for the purpose of propulsion; and nearly all the ships now
built for the Royal Navy are fitted with propellers on his principle.
The annexed diagram represents on a scale of one-eighth of an inch to a
foot, the form of the propeller of the "Agamemnon," of 606-horse power,
which was recently engaged in successfully laying down the Atlantic
Telegraph cable. The diameter of the screw is 18 feet, and the pitch 20
feet.

The screw propeller possesses great advantages in ships of war, as
it is not exposed to damage by shot, and it leaves the entire deck
clear for mounting guns. It has also the further advantage of not
interfering with the working of sails, and is, therefore, admirably
adapted for sea-going ships that economize fuel by alternately steaming
and sailing, as the wind is adverse or favourable. The commotion in
the water made by paddle-wheels, which is an objection to their use in
narrow rivers, is avoided by screw propellers, which being immersed
under the water, make little agitation on the surface, and the ships
move along without any apparent impelling power.

The speed of ships with the best constructed screw propellers is fully
equal to that of paddle-wheel vessels; and when two vessels of the same
size, and with engines of equal power, one fitted with paddles, and the
other with the screw, are fastened stem and stern together, in a trial
of strength, the screw propeller has been found to have the advantage,
and to pull its antagonist along at the rate of one or two miles an
hour.

The difficulty at first experienced in the application of the screw
propeller was to communicate a sufficiently rapid motion to the shaft
to which it is fixed; but, by the employment of direct-acting engines,
this difficulty has been for the most part overcome. The power is
generally first applied to drive a large cog-wheel, the teeth of which
take into the teeth of a smaller cog-wheel fixed to the propeller
shaft, and in this manner the velocity is sufficiently increased.

In 1852 the proportion of screw to paddle-wheel vessels building
in the Clyde was as 43 to 30. The advantages of the propeller are
becoming every year more appreciated, and it is rapidly superseding the
paddle-wheel.

In the steam-boats of the United States the engines are constructed on
the high-pressure principle; and by working with steam of the pressure
of 100 pounds on the square inch, and with larger paddle-wheels, their
boats attain a speed exceeding sixteen miles an hour. But numerous
explosions of boilers on the North American rivers have operated
as a caution against the introduction of high-pressure engines in
steam-boats in this country. The dread of high-pressure steam was early
impressed by the destructive explosion of the boiler of a steam-vessel
at Norwich in 1817, which led to a long parliamentary inquiry into
the subject; and the subsequent loss of life by the explosion of the
"Cricket" on the Thames, has tended to strengthen the apprehension
of high-pressure steam engines. For river use, however, when fresh
water is always at command for generating the steam, there appears to
be no more cause for fear of high-pressure engines in boats than on
railways, provided the boilers are constructed with sufficient care.
The experiments made by Mr. Fairbairn on the strength of boilers,
the results of which were communicated at the meeting of the British
Association in 1853, prove, that by increasing the number and strength
of the "stays," or internal supports, of the boilers, they may be made,
if sufficiently strong, to resist any possible pressure; and that the
square shape, which was supposed to be the weakest, offers, on the
contrary, peculiar facilities for giving increased strength. In one
of these experiments made to determine the ultimate strength of the
flat surfaces of boilers, when divided into squares of sixteen inches
area, the boiler did not give way until it had sustained the enormous
pressure of 1,625 pounds on the square inch.

It might be desirable, in the construction of steam boilers, to adopt
the same principle that is introduced in the building of gunpowder
mills, one-half of which is built in strong masonry, whilst the other
is made of wood. By this means, when an explosion does occur, much
less damage is done, for the lighter part only is blown away, which
does little injury. In the same manner, steam engine boilers might
be constructed with a small portion comparatively weaker, so that if
it gave way there would not be much damage done. Safety-valves are
intended to act in that manner; and if they were properly constructed,
they would sufficiently answer the purpose, and guard against the
possibility of danger; but the numerous accidents that occur with
boilers provided with imperfect safety-valves, show that there is
a necessity for some more effectual protection. Engineers are not
sufficiently alive to the importance of improvements in this respect.
They supply an engine with safety-valves, which would answer the
purpose if kept in proper condition; but they do not make effectual
provision against careless management and reckless misconduct. Some
years since, a gentleman in America sent to the author a description,
with drawings, of a safety-valve that combined the principles of the
safety-plug without its inconvenience; it being so contrived that
when the boiler became too hot, it melted some fusible metal which
previously held down the valve, and then a weight pulled it open to
allow an ample escape of steam; but when the heat was lowered, the
valve again closed. This was shown to an eminent engineer for his
opinion. He pronounced it to be very ingenious, and that it would, no
doubt, answer the purpose; but he said, "_An improved safety-valve is
not wanted_, those in use being quite sufficient for the purpose."

In steam-ships, where salt water is used for generating the steam, the
incrustation on the sides of the boilers becomes a serious annoyance.
It obstructs the communication of heat from the furnace to the water,
and the metal is thus liable to become red-hot. Numerous plans have
been adopted for the purpose of preventing the accumulation of salt
on the sides of the boiler, the most common of which is to allow the
water, when saturated with saline matter, to escape, and then to fill
the boiler afresh. Among other contrivances for effecting the same
purpose, without the waste of heating power which the change of
water occasions, is Mr. Hall's plan of condensing the steam in dry
condensers, cooled externally, so that the distilled water may be used
again and again. This plan though theoretically good, is not much
adopted; for the condensation of steam cannot be so well accomplished
by that means as when a jet of cold water is thrown directly into the
condenser. The principle of the dry condenser has, however, been lately
made available in a new kind of engine, wherein the combined action of
steam and of spirit vapour is applied as the propelling power.

Steam-boats had been for many years in extensive use on the rivers and
seas of Europe and America before it was thought practicable to make
voyages in them across the Atlantic. At the meeting of the British
Association at Liverpool in 1837, that subject was brought forward for
consideration, and it was then attempted to be shown, by calculations
of the quantities of coal requisite for such a voyage, that steam
communication with America would not be profitable, if it could be
accomplished, as the coal would occupy so much of the tonnage as to
leave scarcely any space for passengers and goods. Within a few months
afterwards those calculations were set at nought by the "Sirius" and
the "Great Western," which successfully crossed the Atlantic with
passengers and cargo, the former in nineteen days from Cork, and the
latter in sixteen. At the present time, steam-packets are constantly
crossing from New York to Liverpool in eleven days.

Steam-ships now find their way to India and even to Australia, though
the necessity of taking in coals at depôts supplied from England
not only prolongs the time, but adds so materially to the cost, as
to render steam communication with those distant places scarcely
practicable with profit, since no freight can pay for the expense of
coaling under such circumstances. To overcome that difficulty, it
was proposed to build ships large enough to carry a supply of coals
sufficient for the voyage there and back. One of those ships has
been built for the Eastern Steam Navigation Company by Mr. J. Scott
Russell, from the plans of Mr. Brunel, which is 675 feet long, 83 feet
broad, and 60 feet deep. It is adapted to carry 6,000 tons burthen,
in addition to the engines and requisite quantity of fuel, and to
accommodate 2,000 passengers. This monster ship has been built on what
is called the "wave principle" of ship-building, with long concave
bows. It is to be propelled by the combined powers of the paddle-wheel
and the screw. The engines for the former consist of 4 oscillating
cylinders, 16 feet long and 74 inches in diameter, and the screw is
to be worked by 4 separate engines, with cylinders of 84 inches in
diameter. The speed which the "Great Eastern" is estimated to attain
is 24 miles an hour, and it is calculated that the voyage to Australia
will be accomplished in 30 days. There seems, at present, but small
prospect of those calculations being realized, for the great cost
incurred in launching the vessel and other expenses have exhausted the
funds of the company by whom the ship was constructed.

Another company has, however, been formed for the purpose of
completing, if possible, this great experiment in Steam Navigation;
and the opinion so strongly expressed by Mr. Fairbairn at the recent
meeting of the British Association at Leeds, of the strength of the
monster ship, will give additional stimulus to their exertions. The
ship is built on the same principle of construction as the Britannia
Bridge over the Menai Straits, and it was stated by Mr. Fairbairn that
it might be supported out of water, either in the centre or at each
end, without injury.




STEAM CARRIAGES AND RAILWAYS.


No invention of the present century has produced so great a social
change as Steam Locomotion on railways. Not only have places that were
formerly more than a day's journey from each other been made accessible
in a few hours, but the cost of travelling has been so much reduced,
that the expense has in a great degree ceased to operate as a bar to
communication by railway for business or pleasure.

Though the coaching system in this country had attained the highest
degree of perfection, a journey from London to Liverpool, previously
to the formation of railways, was considered a serious undertaking.
The "fast coach," which left London at one o'clock in the day, did not
profess to arrive in Liverpool till six o'clock the following evening,
and sometimes it did not reach there till ten o'clock at night; and the
fare inside was four guineas, besides fees to coachmen and guards. The
same distance is now performed in six hours, at one-third the expense,
and at one-fourth the fatigue and inconvenience.

Railway Locomotion, however, forms no exception to the rule, that
most modern inventions have their prototypes in the contrivances
of ages past. They were used upwards of two hundred years before
locomotive engines were known, or before the steam engine itself was
invented. The manifest advantage of an even track for the wheels
long ago suggested the idea of laying down wood and other hard,
smooth surfaces for carriages to run upon. They were first applied
to facilitate the traffic of the heavily laden waggons from the coal
pits; the "tramways," as they were called, being formed of timber
about six inches square and six feet long, fixed to transverse timbers
or "sleepers," which were laid on the road. These original railways
were made sufficiently wide for the wheels of the waggons to run upon
without slipping off; the plan of having edgings to the rails, or
flanges to the wheels, not having been adopted till a later period.
To protect the wood from wearing away, broad plates of iron were
afterwards fixed on the tramways.

Cast iron plate rails were first used in 1767. The flat plates on which
the wheels ran were made about three inches wide, with edges two inches
high, cast on the near side, to keep the wheels of the "trams" on the
tracks. These iron plates were usually cast in lengths of six feet, and
they were secured to transverse wooden sleepers by spikes and oaken
pegs. The tramways were laid down on the surface of the country without
much regard to hills and valleys, the horses that drew the trains being
whipped to extra exertion when they came to a hill, and in descending
some of the steep inclines, the animals were removed, and the loaded
waggons were allowed to descend the hills by their own gravity, the
velocity being checked by a break put on by a man who accompanied them.

The chief use of the tramways was to facilitate the conveyance of
coals from the pits to the boats; and as the level of the pit's
mouth was higher than that of the water, it was an object, in laying
down a tramway, to make a continuous descent, if possible, for the
loaded trains to run down, the dragging back of the empty ones being
comparatively easy. Thus, though "engineering difficulties" were
not much considered in the construction of those early railways,
engineering contrivances were adopted to diminish the draught, by
making the gradients incline in one direction.

Soon after the invention of the Steam Engine had been practically
applied to mining purposes, its power was directed to draw the coal
waggons on railways. This was done about the year 1808; and, in
the first instance, the application of steam power was limited to
drawing the loaded waggons up steep inclines. A stationary engine was
erected at the top of the incline, and the waggons were drawn up by a
rope wound round a large drum. This mode of traction was afterwards
extended, in many instances, along the whole railway, so as to
supersede the use of horse power. The employment of stationary engines
in this manner was continued, even after the invention of locomotive
steam engines, to draw the trains up inclines that were too steep for
the power of the small locomotives at first used to surmount; nor has
this plan been yet altogether abandoned.

The application of steam to the direct propulsion of carriages was
a comparatively slow process. It was, indeed, contemplated by Watt,
as a substitute for horse power on common roads, though he does not
seem to have contrived any means by which it might be done. The first
known application of the kind was made by Mr. Murdoch, an engineer in
the employment of Messrs. Boulton and Watt, who in 1784 constructed a
working model of a steam carriage, still preserved, and which formed
one of the most interesting objects in the Great Exhibition of 1851.
The boiler of this model locomotive is made of a short length of brass
tube, closed with flat ends. The furnace to generate the steam consists
of a spirit lamp. The steam is conducted directly from the boiler to a
single cylinder, which is mounted on a pivot near the centre, so that
by the movement of the cylinder the piston-rod may adapt itself to the
varying positions of the crank. The two hind wheels are fixed to the
axle, and on the latter is the crank, attached to the piston-rod. A
single wheel in front serves to guide the carriage, which is propelled
by the rotation of the two hind wheels. The elastic force of the steam
is directly applied as the moving power; and after it has done its work
in the cylinder, it is allowed to escape into the air.

This first known application of steam as a locomotive power is more
perfect in its general arrangements than many steam carriages that
were subsequently brought into operation; and in the plan of balancing
the cylinder on pivots, we perceive the origin of the oscillating
engines, which have been recently introduced with much success in Steam
Navigation. By that arrangement there is attained the most direct
application of the piston-rod to the crank, with the least loss of
power.

Mr. Murdoch's intention was to employ such carriages on common roads,
but he did not proceed to put his plan into operation. Several other
engineers, among whom was Symington--who, as we have before seen,
took an active part in the invention of Steam Navigation--afterwards
endeavoured to realize Mr. Murdoch's ideas on a working scale; but the
first who succeeded in making a locomotive engine, that ran with any
success, were Messrs. Trevethick and Vivian. In 1804 they constructed a
locomotive engine, which was employed on a mineral railway at Merthyr
Tydvil, in South Wales. The boiler of their engine resembled the one
in Mr. Murdoch's model, in having circular flat ends; but, to increase
the heating surface, a flue was introduced in the middle of the boiler,
which passed through it and back again, in the shape of the letter
U. The lower part of the tube formed the furnace, and the upper part
returned through the boiler into the chimney. The steam was admitted
into and escaped from the cylinder by the working of a four-way cock,
the contrivance of the slide-valve being then unknown. On the axle of
the crank a cog-wheel was fixed, and, by means of the usual gearing, it
communicated motion to the hind wheels, which were fixed to the axle,
so that when the wheels revolved the carriage was propelled.

It is a remarkable fact that this engine of Mr. Trevethick's presents
the first practical application of high-pressure steam as a motive
power. Watt had, indeed, suggested the application of the impulsive
power of steam, and Mr. Murdoch's model locomotive was necessarily
constructed on that principle; but until Mr. Trevethick's locomotive
engine was in action, no application of high-pressure steam had been
made on a working scale.

The projectors of locomotive engines were for many years possessed with
the notion that it was necessary to have some contrivance to prevent
the wheels from slipping on the road, as it was supposed that otherwise
the wheels would be turned without moving the carriage. Numerous plans
were devised for overcoming this imaginary difficulty; and though
experience proved that even on railways the adhesion of the wheels was,
in ordinary circumstances, sufficient, yet various schemes continued
to be tried for the purpose of facilitating the ascent of hills.
The imitation of the action of horses' hoofs was one of the means
attempted, but such additional aids were eventually found to be of no
avail, and were discontinued.

All the endeavours that were made, in the first instance, to apply
steam power to locomotion, had in view the propulsion of carriages
on common roads, the idea of constructing level railways through the
country, for facilitating the general traffic, being looked upon as
too visionary a project to be realized. The inventors of locomotive
engines consequently directed their attention almost exclusively to the
arrangement that would best apply steam power to overcome the varying
obstacles and undulations of common roads.

It is very curious and interesting, in tracing the progress of an
invention, to observe the different phases through which it has passed,
before it has been brought into the state in which it is ultimately
applied. It not unfrequently happens that the original purpose sinks
into insignificance, and is almost lost sight of, as the invention
becomes more fully developed. Other objects, that were not perceived,
or were considered altogether impracticable, present themselves, and
are then pursued; and the invention, when perfected, is very different
from its original design. Thus the endeavours of the first inventors of
Steam Navigation were confined to the construction of steam-tugs that
would propel the boats along canals, or take a ship into harbour, the
notion of fitting a steam engine into a ship to propel it across the
sea not having been thought of. In the same manner, the invention of
Steam locomotion on railways was either not contemplated in the first
instance, or was considered very subordinate to the construction of
carriages to be propelled by steam power on common roads.

Among the most successful of those engineers, who constructed steam
carriages to run on roads, were Mr. Gurney, Mr. Birstall, Mr.
Trevethick, Mr. Handcock, and Colonel Maceroni. Mr. Gurney was one of
the first on the road. His steam carriage completed several journeys
very successfully, and proved the practicability of employing steam
power in locomotive engines many years before the first passenger
railway was brought into operation. This, like all other new
inventions, was, however, beset with difficulties, among which the
most annoying was the determined obstruction the plan met with from
the trustees of public roads, who levied heavy tolls on the carriages,
and laid loose stones on the roads to stop them from running, as the
driving wheels were found to be destructive to the roads. There was
also considerable danger in running steam carriages on the same roads
on which ordinary traffic was conducted, because the strange appearance
of the engines, their noise, and the issuing steam, frightened the
horses.

Notwithstanding these difficulties, the importance of applying steam
as a locomotive power for passenger traffic became so apparent, that a
Committee of the House of Commons was appointed in 1831, to consider
whether the plan could be adopted with safety on common roads, and
whether it should not be encouraged by passing an Act of Parliament for
regulating the tolls chargeable on such carriages, and for preventing
the obstructions to which they had been exposed. The evidence given
before the Committee was greatly in favor of steam carriages, and
tended to show that there was no insuperable difficulty to the general
adoption of them. The Committee accordingly reported as follows:--

"Sufficient evidence has been adduced to convince your Committee--

"1st. That carriages can be propelled by steam on common roads at an
average speed of ten miles an hour.

"2nd. That at that rate they have conveyed upwards fourteen passengers.

"3rd. That their weight, including engines, fuel, water, and
attendants, may be under three tons.

"4th. That they can ascend and descend hills of considerable elevation,
with facility and safety.

"5th. That they are perfectly safe for passengers.

"6th. That they are not (or need not be, if properly constructed)
nuisances to the public.

"7th. That they will become a speedier and cheaper mode of conveyance
than carriages drawn by horses.

"8th. That as they admit of greater breadth of tire than other
carriages, and as the roads are not acted upon so injuriously as by the
feet of horses in common draught, such carriages will cause less wear
of roads than coaches drawn by horses.

"9th. That rates of toll have been imposed on steam carriages which
would prohibit them being used on several lines of roads, were such
charges permitted to remain unaltered."

In defiance of this favourable report, experience proved that there
were defects in that system of locomotion greater than its advocates
were disposed to admit, and that the mechanism was frequently broken
or disarranged by the constant jarring caused by the roughness of
the road. The alarm of the horses drawing other carriages was also
calculated to produce fearful accidents.

So far, indeed, as regarded the power of locomotion, the steam
carriages were successful. The author was witness of this success
during a short excursion in Colonel Maceroni's carriage, which ascended
hills and ran over rough roads with great ease, and at a speed of
twelve miles an hour. The practical difficulties, however, were so
great, that steam carriages have not been able to compete with horse
power; for the original cost of the boiler and engine, the necessary
repairs, and the expense of fuel, amounted to more than the cost and
keep of horses. The plan was practically tried for several weeks, in
1831, by running a steam carriage for hire from Paddington to the Bank
of England. The carriage, of which the annexed diagram is an outline,
was one of those constructed by Mr. Handcock. The engine was placed
behind the carriage, which was capable of containing sixteen persons,
besides the engineer and guide. The latter was seated in front, and
guided the carriage by means of a handle, which turned the fore wheels.
The carriage was under perfect control, and could be turned within
the space of four yards. With this carriage, Mr. Handcock stated he
accomplished one mile up hill at the rate of seventeen miles an hour.
The carriage loaded very well at fares which would now be considered
exorbitant, but the frequent necessity for repairs rendered the
enterprise unsuccessful, and the steam carriage was taken off the road.

[Illustration]

The successful establishment of railways, and the great advantages
arising from them compared with the ordinary means of conveyance,
still further reduced the chance of establishing Steam Locomotion
on roads, and the plan is now in abeyance, at least, if it has not
been abandoned. It is very possible, however, that in the progress of
invention, modifications may be made in the steam engine, to adapt it
more successfully to the purpose; or more suitable motive powers may be
discovered, that may bring mechanical locomotion on roads again into
favour.

The successful application of Steam Locomotion on railways cannot be
dated more than thirty years ago; yet in that short period its progress
has been so rapid, that but few traces of the old mode of travelling by
stage coaches are now to be seen.

Some locomotive steam carriages had, indeed, been introduced on the
Stockton and Darlington coal railway, by Mr. George Stephenson, in
1825, but their results were not so satisfactory as to induce the
extension of the plan to the other railways that were then laid down
in the coal districts of England. The cylinders of those engines were
vertical, and each of the four wheels acted propulsively on the rails
by means of an endless chain running along cog-wheels fixed on the
axles. The utmost speed that could be obtained by this means was eight
miles an hour; and so little were these engines calculated to solve
the problem of the practicability of steam locomotive engines, that
when the first passenger railway was projected, from Liverpool to
Manchester, it was proposed to propel the carriages by the traction
of ropes, put in motion by stationary steam engines. The directors,
before finally determining on the system of locomotion to be adopted,
offered a premium of £500 for the best locomotive engine to run on that
line. The stipulations proposed, and the conditions which the required
engines were to fulfil, may be regarded as a curious exposition of the
limited views then taken of the capabilities of Steam Locomotion on
railways. The engine "was to consume its own smoke; to be capable of
drawing three times its own weight at 10 miles an hour, with a pressure
on the boiler not exceeding 50 pounds on the square inch; the whole to
be proved to bear three times its working pressure--a pressure guage
to be provided; to have two safety-valves, one locked up; the engine
and boiler to be supported on springs, and rested on six wheels, if
the weight should exceed 4½ tons; height to the top of the chimney not
to exceed 15 feet; weight, including water in boiler, not to exceed 6
tons, or less, if possible; the cost of the engine not to exceed £550."

An engine, called the "Rocket," constructed by Messrs. Booth and
Stephenson, was the successful competitor for the prize. It so far
exceeded the required conditions as to speed, that, when unattached to
any carriages, it ran at the rate of 30 miles an hour. The principal
cause of its successful action was the introduction of a boiler
perforated lengthwise by many tubes, through which the heated air of
the furnace passed to the chimney, and by this means a much larger
evaporating surface was obtained than in the boilers previously
employed, with a single flue passing through the centre. The tubes were
of copper, three inches in diameter, one end of each communicating with
the chimney, and the other with the furnace. There were twenty-five of
these tubes passing through the boiler, and fixed water-tight at each
end.

The boiler was 3 feet 4 inches in diameter, and 6 feet long; and it
exposed a heating surface of 117 square feet. There were two cylinders,
placed in a diagonal position, with a stroke of 16½ inches, and each
worked a wheel 4 feet 8½ inches diameter, the piston-rod being attached
externally to spokes of the driving wheels. The draught of the chimney,
aided by the escaping steam from the cylinders, which was admitted into
it, served to keep the fuel in active combustion. The "Rocket" weighed
41 tons; the tender, with water and coke, 3 tons 4 cwt.; and two loaded
carriages attached, 9½ tons; so that the engine and train together
weighed about 19 tons. The boiler evaporated 114 gallons of water in
the hour, and consumed, in the same time, 217 pounds of coke. The
average velocity of the train was 14½ miles per hour.

The accompanying woodcuts represent an elevation of the "Rocket,"
and a section of its boiler. In these figures, _a_ is the fire-box
or furnace, surrounded on all sides with water, with the exception
of the side perforated for the reception of the tubes; _b_ is the
boiler; _d_, one of the steam cylinders; _e_, the chimney; _h_ and _i_,
safety-valves; _f_, one of the connecting rods for communicating motion
to the driving wheels.

[Illustration]

Three other engines competed with the "Rocket," two of which had
attained great speed on previous trials. These were the "Novelty,"
constructed by Messrs. Braithwaite and Ericsson, which weighed only
2¾ tons; and the "Sans Pareil," manufactured by Mr. Arkworth, which
weighed 4½ tons. On the day of trial, the 6th of October, 1829, these
two locomotive engines were disabled by the bursting of some of their
pipes, and thus the field was left clear to the "Rocket," for the
fourth engine had no chance of winning the prize.

The "Rocket," indeed, more than fulfilled all the conditions required
by the directors of the railway, who thereupon decided on employing
locomotive engines for the traffic on the line.

The "Rocket" has formed the model on which all subsequent locomotive
engines have been constructed; for, though numerous alterations and
improvements have been made in details, and though the size of the
engines has been greatly enlarged, the principle of construction
remains essentially the same. Among the improvements that have been
introduced by different inventors, is an increase in the number of
the tubes in the boiler, so as to facilitate the generation of steam,
some of the engines now made having upwards of 100 tubes, though of
smaller diameter than those of the "Rocket." The boilers have also been
elongated, to enlarge the evaporating surface and economize fuel. The
cylinders are placed horizontally, and they are generally fixed inside
the boiler, to prevent the cooling of the steam. The piston-rods are
attached to cranks on the axle, placed at right angles to each other;
and the engines are generally mounted on six wheels, four of which are
driving wheels, made of larger size than the two others, and they are
coupled together by connecting arms. The large and powerful engines on
the Great Western Railway have, however, only two driving wheels, which
are 8 feet in diameter. These engines weigh as much as 31 tons, which
is seven times more than the weight of the "Rocket." They are capable
of taking a passenger train of 120 tons at an average speed of 60
miles an hour on easy gradients; and the effective power, as measured
by a dynamometer, is stated to be equal to 743 horses.

The accompanying engraving of one of the recently constructed engines
on the Great Western Railway presents a remarkable difference in
point of size and general arrangement to the original prototype, from
which, however, it does not materially differ in the principle of its
construction.

[Illustration]

The complete success of the "Rocket" having settled the question of the
mode of traction, the Directors of the Liverpool and Manchester Railway
made increased efforts to complete the line, and to open it for general
traffic. In September, 1830, all was ready for the opening, which it
was determined should take place with a ceremony indicative of the
importance of the great event. The principal members of the Government
consented to take part in the inauguration of the railway, and the
utmost interest was excited throughout the country for the success of
an undertaking that promised to be the commencement of a new era in
travelling. The 15th of September was the day appointed, and there
were eight locomotive engines provided to propel the same number of
trains of carriages, which were to form the procession. All along the
line there were crowds of persons collected to witness the ceremony.
The trains started from the Liverpool end of the railway; and, as they
passed along, they were greeted by the cheers of the astonished and
delighted spectators. On arriving at Parkside, seventeen miles from
Liverpool, the engines stopped to take in fresh supplies of fuel and
water. The passengers alighted and walked upon the line, congratulating
one another on the delightful treat they were enjoying, and on the
success of the great experiment. All hearts were bounding with joyous
excitement, when a disastrous event occurred, which threw a deep gloom
over the scene. The Duke of Wellington, Sir Robert Peel, and Mr.
Huskisson were among those who were walking on the railway, when one of
the engines was recklessly put in action, and propelled along the line.
There was a general rush to the carriages, and Mr. Huskisson, in trying
to enter his carriage, slipped backwards and fell upon the rails. The
wheels of the engine passed over his leg and thigh, and he was so
severely injured, that he expired in a few hours.

Notwithstanding this lamentable occurrence, the journey was continued
to Manchester, and the carriages returned to Liverpool the same
evening. On the following morning the regular trains commenced running,
and they were crowded with passengers, nothing daunted by the fatal
calamity on the opening day.

The immense advantages of this mode of travelling were at once
apparent, and lines of railway in different parts of the country
were quickly projected. The railway from London to Birmingham was
the first one commenced after the completion of the Liverpool and
Manchester line, and a connecting link with Manchester and Liverpool
was also begun by a separate company. The Birmingham Railway was opened
throughout on the 17th September, 1838.

Railway enterprise was not checked by the great cost of the
undertakings, nor by the miscalculations of the engineers, who, in the
first instance, frequently greatly under-estimated the expenditure
requisite for the cuttings, embankments and tunnels, which were thought
necessary to attain as perfect a level as possible. The original
estimate for the Liverpool and Manchester Railway was £300,000, but
the amount expended on the works at the time of opening was nearly
£800,000. The original estimate of the London and Birmingham Railway,
including the purchase of land, and the locomotives and carriages,
was £2,500,000, whilst the actual cost amounted to £5,600,000, the
cost of the works and stations being about £38,000 per mile. The Grand
Junction Railway, from Birmingham to Liverpool, was more economically
constructed, because the difficulties to be surmounted were not so
great, and less attention was paid to maintain a level line. It was
estimated to cost, including all charges, £13,300 per mile, though the
actual cost was £23,200.

The plan adopted for laying down and fixing the rails on all the
railways in England, with the exception of the Great Western, is
nearly similar to that on which the original coal-pit railways were
constructed. Pieces of timber, called "sleepers," are laid at short
distances across the road, and on to these sleepers are fixed cast iron
"chairs," into which the rails are fastened by wedges, the sleepers
being afterwards covered with gravel or other similar material, called
"ballast," to make the timbers lie solidly, and to keep the road dry.

The railway system of Great Britain was commenced without sufficient
attention to the determination of the best width apart of the rails.
In forming the Liverpool and Manchester Railway, the guage of the
railways in the collieries was adopted, and the width between the rails
was made 4 feet 8½ inches. The same width of rails was adopted on the
London and Birmingham and Grand Junction Railways; and as uniformity of
guage was essential to enable the engines and carriages on one line to
travel on another, the other railways connected with the grand trunk
line were made of the same width of guage. Mr. Brunel, the engineer
of the Great Western Railway, departed from that uniformity, and laid
down the rails 7 feet apart. The increased width of guage possesses
many advantages, of which greater steadiness of motion and greater
attainable speed, without risk, are the most important; but, at the
same time, the additional space incurs a greater expense in laying out
the line. As branches from the Great Western Railway spread into the
districts where the narrow guage railways had been laid down, much
inconvenience has arisen from the break of guage, as it occasions the
necessity for a change of carriages. On some railways, to avoid this
inconvenience, narrow and broad guage rails have been laid down on the
same line.

If the railway system of Great Britain were to be recommenced, after
the experience that has now been acquired, the medium guage would most
probably be adopted; and in commencing to lay down railways in Ireland,
the Irish Railway Commissioners recommended 6 feet 2 inches as the most
desirable width, and that standard has been advantageously adopted in
the sister country.

Travelling experience tells greatly in favour of the broad gauge. There
is no railway out of London whereon the carriages run so smoothly, and
on which the passengers are so conveniently accommodated, as on the
Great Western. The speed attained on that railway also surpasses that
on any other. The express train runs from London to Bristol, a distance
of 120 miles, in less than three hours. The author accompanied an
experimental train, when one of the large engines was first put upon
the line, and during some portion of the journey a rate of 70 miles an
hour was accomplished without any inconvenient oscillation.

It must be observed, with regard to the action of locomotive engines,
that as the piston-rods are attached directly to cranks on the axle,
each piston makes a double stroke for every revolution of the driving
wheels; consequently, when the engine is running at great speed, the
movement of the piston is so rapid, that there is neither time for
the free emission of the waste steam, nor for the full action of the
high-pressure steam admitted. There is, therefore, a great waste of
power occasioned by the admitted steam having to act against the steam
that is escaping; and an engine, calculated to have the power of 700
horses, will not exert a tractive force nearly equal to that amount.
With a driving wheel 6 feet in diameter, a locomotive engine will be
propelled 18 feet by each double stroke of the piston, if there be no
slipping on the rails; consequently, in the space of a mile, the piston
must make 300 double strokes. When running, therefore, at the speed of
30 miles an hour, the piston makes 150 double strokes per minute.

The success of the great experimental railway from Manchester to
Liverpool not only stimulated similar works in this country, undertaken
by private enterprise; but the Continental Governments quickly
perceived the importance of that means of communication, and commenced
the formation of railways at the national cost, and placed them under
governmental control. Belgium was peculiarly adapted, by the general
level state of the country, for the formation of railways; and long
before any connected system was completed in this country, the _chemins
de fer_ formed a complete net-work in that kingdom, and the system of
conducting the traffic was brought to a much higher state of perfection
than was attained in this country. The rate of travelling, however, was
slower.

It is a question that has been often mooted, whether it is better
to allow the system of communication throughout the country to be
conducted by independent companies of enterprising individuals, or
to place it entirely under the control of the Government. The want
of system manifested in the formation of the railways in England
has proved a serious inconvenience, and has occasioned wasteful
expenditure, besides having led to a fearful destruction of life,
owing to the want of careful attention to the means of safety, and to
ill-judged parsimony in the management of the traffic. There can be
no doubt that if the Government had undertaken the work zealously,
and with the view of establishing a complete system of railway
communication, many of the inconveniences now experienced might have
been avoided, and the railways might have been laid down and worked
at considerably less cost, and with a large addition to the national
revenue. There is, however, so strong a disinclination in this country
to the centralization of Government power, and to the extension of
Government influence, that the people generally had rather submit
to considerable inconvenience and expense, than tolerate the system
of railway management which has been adopted on the Continent. The
necessity of interference, to protect the interests of the public, has
nevertheless compelled the Government, though late, to adopt measures
for controlling the management of the railway companies, and stringent
regulations are now imposed with a view to prevent unnecessary danger
to railway passengers.

The railway system of Great Britain, though established entirely by
private enterprise, represents an amount of capital equal to one-third
of the national debt, and nearly 100,000 individuals are directly
employed in conducting the traffic on the various railways in this
kingdom. An idea of the vastness of these undertakings, and the
important interests involved in them, may be formed from the following
facts, stated by Mr. Robert Stephenson, at the Institution of Civil
Engineers:--

"The railways of Great Britain and Ireland, completed at the beginning
of 1856, extended 8,054 miles, and more than enough of single rails
were laid to make a belt round the globe. The cost of constructing
these railways had been £286,000,000. The working stock comprised 5,000
locomotive engines and 150,000 carriages and trucks; and the coal
consumed annually by the engines amounted to 2,000,000 tons, so that
in every minute 4 tons of coal flashed into steam 20 tons of water.
In 1854 there were 111 millions of passengers conveyed on railways,
each passenger travelling an average of 12 miles. The receipts during
1854 amounted to £20,215,000; and there was no instance on record in
which the receipts of a railway had not been of continuous growth,
even where portions of the traffic had been abstracted by new lines.
The wear and tear of the railways was, at the same time, enormous. For
instance, 20,000 tons of iron rails required to be annually replaced,
and 26 millions of wooden sleepers perished in the same time. To supply
this number of sleepers, 300,000 trees were felled, the growth of which
would require little less than 5,000 acres of forest land. The cost of
running was about fifteen pence per mile, and an average train will
carry 200 passengers. Without railways, the penny post could not have
been established, because the old mail coaches would have been unable
to carry the mass of letters and newspapers that are now transmitted.
Every Friday night, when the weekly papers are published, eight or ten
carts are required for Post Office bags on the North-Western Railway
alone, and would hence require 14 or 15 mail coaches."

Adverting to other advantages derived from railway locomotion, Mr.
Stephenson noticed the comparative safety of that mode of travelling.
Railway accidents occurred to passengers in the first half of 1854 in
the proportion of only one accident to every 7,194,343 travellers.
As regards the saving of time, he estimated that on every journey,
averaging 12 miles in length, an hour was saved to 111 millions of
passengers per annum, which was equal to 38,000 years, reckoning eight
working hours per day; and allowing each man an average of 3s. a day
for his work, the saving of time might be valued at £2,000,000 a year.
There were 90,000 persons employed directly, and 40,000 collaterally,
on railways; and 130,000 men, with their families, represent 500,000 so
that 1 in 50 of the entire population of the kingdom might be said to
be dependent for their subsistence on railways.

Every year adds to the extent of the railway system, and to the
increase of the traffic, so that considerable addition should be made
to the amounts stated by Mr. Stephenson to represent the state of
railway enterprise and railway traffic at the present day. The traffic
returns for the week ending the 25th of September, 1858, amounted
to £502,720; and the gross receipts of the railways in 1857 were
£24,174,610. The railways now open for traffic in England, Scotland,
and Ireland extended to upwards of 9,000 miles, and the lines reported
to be in the course of construction amount to one-ninth the length of
those completed.

In estimating the importance and advantage of railway travelling, there
must not be omitted its cheapness and comfort, compared with travelling
by stage coach. There are some persons, indeed, who look back with
regret to the old coaching days; and it must be admitted that railways
have taken away nearly all the romance of travelling, and much of the
exhilarating pleasure that was experienced when passing through a
beautiful country on the top of a well-horsed coach in fine weather.
The many incidents and adventures that gave variety to the journey were
pleasant enough for a short distance; but two days and a night on the
top of a coach, exposed to cold and rain, or cramped up inside, with
no room to stir the body or the legs, was accompanied with an amount of
suffering which those who have experienced it would willingly exchange
for a seat, even in a third-class railway carriage. In a national and
in a social point of view, also, railways have produced important
improvements. They tend to equalize the value of land throughout the
kingdom, by bringing distant sources of supply nearer the points of
consumption; they have given extraordinary stimulus to manufacturing
industry; and by connecting all parts of the country more closely
together, railway communication has concentrated the energies of the
people, and has thus added materially to their wealth, their comforts,
and to social intercourse.

Nor must we, in noticing the grand invention of locomotion on
railways, omit to mention some of the many subsidiary works which
have been created during its progress towards perfection, and which
have contributed to its success. Tunnels, of a size never before
contemplated, have penetrated for miles through hard rocks, or through
shifting clays and sands; embankments and viaducts have been raised
and erected, on a scale of magnitude that surpasses any former similar
works; bridges of various novel kinds, invented and constructed for
the special occasions, carry the railways over straits of the sea,
through gigantic tubes; across rivers, suspended from rods supported by
ingeniously devised piers and girders; and over slanting roads, on iron
beams or on brick arches built askew. As to the locomotive engines,
though the principle of construction remains the same, the numerous
patents that have been obtained attest that invention has been active
in introducing various improvements in the details of construction,
to facilitate their working, and to increase their power. The various
plans that have been contrived for improving the structure of the
wheels and axles, for the application of breaks, for deadening the
effect of collisions, for making signals, for the forms of the rails,
and for the modes of fastening them to the road, are far too many to be
enumerated.

In addition to the innumerable contrivances that have been invented
for the improvement of the working of ordinary railways, several
distinct systems of railway locomotion have been introduced to public
notice, some of which seemed very feasible, though they have nearly
all gradually disappeared. Of these, the Atmospheric railway was the
most promising, and for a time it bid fair to supersede the use of
locomotive engines. The propulsion of the carriages, by the pressure
of the atmosphere acting on an attached piston working in a vacuum
tube, possessed many theoretical advantages, and if it could be
applied economically, railway travelling would become more pleasant
and more free from danger than it is. On several lines of railway the
atmospheric plan was put into operation, but owing to the expense of
working, it was gradually abandoned. The short line from Kingston to
Dalky, in Ireland, up a steep incline, was favourable to the working of
the atmospheric railway, and there it continued to linger for some time
after it had been abandoned elsewhere.

It is to be regretted that the atmospheric railway should have failed
in economical working, for it possessed greater advantages for general
traffic than the ordinary locomotive railway trains; and it is probable
that if the same amount of inventive power and industry, which have
been bestowed in improving locomotive engines, had been directed to
overcome the difficulties of atmospheric traction, it might have proved
economically successful.

The facility of travelling by railway has excited a spirit of
locomotion before undreamed of. Instead of the diminished demand for
horses which was apprehended when railways displaced stage coaches,
public conveyances have increased a hundredfold. We can now scarcely
conceive the time when there was not an omnibus in the streets of
London, yet, scarcely more than thirty years ago, they were unknown,
and travelling by stage carriages from one part of the town to another
was prohibited by law! On their first introduction, omnibuses were
considered absurdities, and were ridiculed as "painted hearses." The
present omnibus traffic in London alone amounts to nearly £20,000 per
week.




THE AIR ENGINE.


Numerous attempts have been made to supersede steam as a motive power,
with the view to avoid the loss of heat by its absorption in the steam
in a latent state. Mercury vapour and spirit vapour have been tried,
in the expectation that as they possess much less capacity for heat,
an equal pressure might be obtained, with a diminished loss of heating
power. Several gaseous agents have been applied to the same purpose, of
which carbonic acid gas seemed to present the best prospect of success,
because it becomes expanded with a comparatively small increase of
temperature. None of these attempts to produce a motive power superior
to steam have yet proved successful. They have all, after a short
season of promise, dropped out of notice; and the only one that is
still in the field, struggling for superiority, is the air engine.

The first known air engine was invented by Sir George Cayley, in 1803.
In his engine the air was heated by passing directly through the hot
coals of the furnace, which some engineers yet consider to be the best
mode of expansion; but its operation did not answer expectations. Mr.
D. Stirling, of Dundee, afterwards improved on Sir George Cayley's
plan, and introduced a method of regaining the heat from the expanded
air, after it had done its work in the cylinder, and of applying it to
expand the air again. Engines on this construction have been for some
years working in Scotland, and in 1850 Mr. Stirling took out a patent
for an improvement in the arrangement, which is stated to have been
very successful.

Though Sir George Cayley and Mr. Stirling were the first in the field
as inventors of air engines, the name of Mr. Ericsson, an American,
is more closely associated with the invention, as he has for many
years been conducting experiments on a large scale, and has tried his
"caloric engine" on land, and on a ship of large burthen, built for the
purpose.

The principle and the working of Mr. Ericsson's caloric engine is
nearly the same as Mr. Stirling's; but as it has been brought most
prominently into notice, we shall direct attention more particularly
to its construction and performances. Mr. Ericsson obtained a patent
for his caloric engine in this country in 1833, and a subsequent patent
for improvements on it was taken out in 1851. During those years, and
to a late period, he was indefatigably working out the principle, and
numerous highly favourable reports have from time to time been made of
the results of the experiments; but the advantages to be derived from
the air engine remain nevertheless very questionable.

The object attempted to be gained is to make the same heating power
do its work again and again. Atmospheric air, after being expanded by
passing over an extensive hot surface, exerts the force thus acquired
to raise the piston of a large cylinder, and it is then attempted
to abstract the heat as the air issues out, and to apply it to the
expansion of a further quantity.

The practicability of this plan has undergone much discussion; its
friends and foes being equally confident in their opinions. The
former pronounce it to be one of the most valuable inventions of
the age, being calculated to economize heat, and to give greatly
additional impulse to navigation; whilst its opponents declare that the
calculations are erroneous, the experiments fallacious, and that the
expanded air consumes more heating power than steam.

In one of the favourable notices of Mr. Ericsson's engine in an
American publication, it is thus described:--"Two caloric engines have
been constructed in New York, one of 5-horse power, the other of 60.
The latter has four cylinders; two of 6 feet diameter, placed side by
side, surmounted by two of much smaller size. Within are pistons, so
connected that those in the lower and upper cylinders move together.
A fire is placed under the bottom of the large cylinders, called the
working cylinders; those above are called the supply cylinders. As
the piston in the supply cylinder moves down, valves at the top admit
the air. As they rise, those valves close, and the air passes into
a receiver and regenerator, where it is heated to about 450°, and
entering the next working cylinder, it is further heated by a fire
underneath to 485°. The air is thus expanded to double its volume;
and supposing the supply cylinder to be half the size of the other,
the air, when expanded, will completely fill the larger cylinder. As
the area of the piston of the smaller cylinder will be only half that
of the larger, and as the air will be of the same pressure in both,
the total pressure on the piston of the large cylinder will be double
that on the small one. This surplus furnishes the working power of
the engine. After the air in the working cylinder has forced up the
piston within it, a valve opens; and as the air passes out, the piston
descends by gravity, and cold air rushes in, and fills the supply
cylinder.

"The most striking feature is the regenerator. It is composed of wire
net, placed together to a thickness of about 12 inches. The side
of the regenerator, near the working cylinder, is heated to a high
temperature. The air passes through it before entering the working
cylinder, and becomes heated to 450°. The additional heat of 30° is
communicated by the fire underneath to the large cylinder. The expanded
air forces the cylinder upwards, valves open, and it passes from the
cylinder, and again enters the regenerator. One side of the regenerator
is kept cool by the air on its entering in the opposite direction at
each stroke of the piston; consequently, as the air of the working
cylinder passes out, the wires abstract its heat so effectually, that
when it leaves the regenerator, it has been robbed of all except about
30°. In other words, as the air passes into the working cylinder, it
gradually receives from the regenerator about 450° of heat; and as it
passes out, this is returned to the wires, and it is thus used over and
over again; the only purpose of the fires beneath the cylinders being
to supply the 30° of heat which are lost by radiation and expansion.

"The regenerator in the 60-horse engine measures 26 inches in height
and width. Each disc of wire composing it contains 676 superficial
square inches, and the net has 10 meshes to the inch. Each superficial
inch, therefore, contains 100 meshes, and there are 67,600 in each
disc; and as 200 discs are employed, the regenerator contains
13,520,000 meshes, with an equal number of small spaces between the
discs as there are meshes; therefore, the air is distributed into
27,000,000 of minute cells. The wire in each disc is 1,140 feet long;
and the total length of wire in the regenerator is 41½ miles, or equal
to the surface of four steam boilers, each 40 feet long and 4 feet
diameter."

The accounts received from America of the great success that had
attended the working of Mr. Ericsson's air engine, on the ship
"Ericsson," attracted much attention in this country, and formed
the subject of two evenings' discussion in the Institution of Civil
Engineers. The most prevalent opinion was, that it is impossible to
regain the heating power without corresponding loss of mechanical force
or the addition of heat, and that there must have been some fallacy in
the reports of the work done and of the quantity of fuel consumed.

It is, indeed, evident that nothing approaching the amount of heat
said to have been recovered could be regained by passing through
the regenerator; for as the apparatus becomes heated by the first
portions of air passing through it, the temperature of the quantity
that afterwards passed must at least be equal to that of the heated
wires, and the last portions of air would consequently scarcely part
with any caloric to the regenerator, previously heated to nearly
its own temperature. Experience has since proved that the notion of
regaining the heat by the regenerator was fallacious, for in the
last improvements in Mr. Ericsson's engine, it is stated that the
regenerator has been abandoned, and the plan has been adopted of
cooling the air as it issues from the large cylinder, by passing it
through tubes surrounded by cold water, and then using the same air
over again.

One great practical inconvenience in the use of the air engine was the
necessity of having enormously large cylinders to attain the required
power, with the low amount of pressure that can be procured by the
expansion of the air. The consequent friction increased the loss of
power, and the difficulty of lubricating the pistons added to the
practical objections to the air engine. To overcome these objections,
the air in Mr. Stirling's engine is compressed before it is heated, by
which means an equal amount of pressure is obtained on a smaller piston.

The air engine would in many respects possess advantages over the steam
engine, if it could be worked economically. The space occupied by the
boilers would be saved, and the danger of explosions would be avoided;
for hot air does not scald, and the quantity at any time expanded would
be too small to do much injury.

A patent has since been obtained by Messrs. Napier and Rankine, for
improvements in the air engine, which they anticipated would remove
the objections that have been raised to the engines of Stirling and
Ericsson. The heating surface has been greatly increased by employing
tubes; and other defects in the former engines, to which their want
of complete success is attributed, have been remedied, so that Mr.
Rankine, in his description of the improvements at the meeting of the
British Association at Liverpool, confidently anticipated to effect a
great saving of heating power, combined with the other advantages of
the air engine. He estimated the consumption of fuel by a theoretically
perfect air engine on Mr. Stirling's principle at 0·37 lbs. per horse
power per hour; whilst a theoretically perfect steam engine would
consume 1·86 lbs. The actual average consumption of a steam engine
is, however, 4 lbs. of fuel per horse power per hour, and the actual
consumption of Stirling's engine is stated by Mr. Rankine to have
been 2·20 lbs, and that of Ericsson's 2·80 lbs. It appears from this
statement, therefore, that the air engines of Messrs. Stirling and
Ericsson are superior in point of economy of fuel to steam engines; and
if Mr. Rankine's anticipations of the superiority of his air engine be
realized, it will effect still greater economy. In Messrs. Napier and
Rankine's engine, the air is compressed before expansion, so that the
size of the cylinders may be reduced to even smaller dimensions than
the cylinders of steam engines of equal power.




PHOTOGRAPHY.


The power we now possess of fixing the transient impression of the rays
of light, and of retaining the beautiful images of the camera obscura,
is perhaps the most astonishing of the present age of wonders. Effects
similar to those of the electric telegraph, of steam navigation, of
dissolving views, and of other wondrous realizations of inventive
genius, had been anticipated in growing tales of Eastern romance
centuries ago; but the most fanciful imagination had not conceived the
possibility of making Nature her own artist, and of producing, in the
twinkling of an eye, a permanent representation of all the objects
comprehended within the range of vision.

Such an idea could scarcely have occurred until after the invention of
the camera obscura; but when looking at the beautiful pictures focused
on the screen of that instrument, it became an object of longing desire
to fix them there.

To trace the history of Photography from its earliest beginnings, we
must go back to the days of the alchemists, who were the discoverers
of the influence of light in darkening the salts of silver, on which
all photographic processes on paper depend. That property of light was
noticed in 1566, and it induced the speculative philosophers of that
day to conceive that luminous rays contained a sulphurous principle
which transmitted the forms of matter. Homberg, more than a century
afterwards, misled by this action of the sun's rays, supposed that they
insinuated themselves into the particles of bodies, and increased their
weight; and Sir Isaac Newton also entertained a similar opinion.

The influence of the solar rays in facilitating the crystallization of
saltpetre and sal ammoniac, was shown by Petit in 1722; and in 1777,
the distinguished chemist Scheele discovered that the violet rays of
the spectrum possess greater power in producing those changes than
any other. A solution of nitrate of silver, then called "the acid of
silver," was known to be peculiarly susceptible to the action of those
rays. The experiment by which it was illustrated consisted in pouring
the solution on chalk, which became blackened by exposure to light.
These discoveries were made by Scheele in his endeavours to find in
light the source of "phlogiston"--that _ignis fatuus_ of the chemists
of the last century. We thus perceive, in the first steps towards the
invention of Photography, one of the many instances of the discovery of
truth in the search after error.

At the beginning of the present century, Mr. Wedgwood, the celebrated
porcelain manufacturer, undertook a series of experiments to fix the
images of the camera, assisted by Mr. (afterwards Sir Humphry) Davy.
They so far succeeded as to impress the images on the screen, but
unfortunately they had not the power of preserving the paper from
being blackened all over when exposed for a short time to the light.
"Nothing," said Sir Humphry Davy, in his account of these experiments,
"but a method of preventing the unshaded parts of the delineation from
being coloured by exposure to light is wanting to render this process
as useful as it is elegant."

It was in June, 1802, that Mr. T. Wedgwood published "an account of a
method of copying paintings on glass, and of making profiles by the
agency of light; with observations by H. Davy." Mr. Wedgwood made use
of white paper or white leather, moistened with a solution of nitrate
of silver. The following description of the process, contributed to
the "Journals of the Royal Institution" by Davy, will be read with
interest, as showing how closely these experiments approximated to
the photogenic process, invented by Mr. Talbot thirty-six years
afterwards:--

"White paper or white leather moistened with a solution of nitrate
of silver undergoes no change in a dark place; but on being exposed
to daylight, it speedily changes colour, and after passing through
different shades of grey and brown, becomes at length nearly black;
the alterations of colour take place more speedily in proportion as
the light is more intense. In the direct rays of the sun, two or three
minutes are sufficient to produce the full effect. In the shade,
several hours are required; and light transmitted through different
coloured glasses acts on it with different degrees of intensity.
Thus it is found that red rays, or the common sunbeams passed through
red glass, have very little action on it. Yellow or green are more
efficacious; but blue and violet light produce the most decided and
powerful effects.

"When the shadow of any figure is thrown on the prepared surfaced, the
part concealed by it remains white, and the other parts speedily become
dark. For copying paintings on glass, the solution should be applied on
leather, and in this case it is more readily acted on than when paper
is used. When the colour has been once fixed on leather or paper, it
cannot be removed by the application of water, or water and soap, and
it is in a high degree permanent. The copy of a painting or a profile,
immediately after being taken, must be kept in a dark place. It may,
indeed, be examined in the shade, but in this case the exposure should
only be for a few minutes; by the light of candles or lamps, it is
not sensibly affected. No attempts that have been made to prevent the
uncoloured parts of the copy or profile from being acted upon by light,
have as yet been successful. They have been covered with a coating
of fine varnish, but this has not destroyed their susceptibility of
becoming coloured; and even after repeated washings, sufficient of the
active part of the saline matter will still adhere to the white parts
of the leather or paper, to cause them to become dark when exposed to
the rays of the sun.

"The woody fibres of leaves, and the wings of insects, may be pretty
accurately copied; and in this case it is only necessary to cause the
direct solar light to pass through them, and to receive the shadows
on prepared leather. Images formed by means of the camera obscura
have been found too faint to produce, in any moderate time, an effect
on nitrate of silver. To copy those images was the first object of
Mr. Wedgwood in his researches on this subject, and for this purpose
he first used the nitrate of silver, which was mentioned to him by a
friend as a substance very sensible to the influence of light; but all
his numerous experiments, as to their primary end, proved unsuccessful."

It will be seen, from the foregoing account of the results of their
experiments, that Mr. Wedgwood's process and the early processes
of Mr. Talbot were nearly alike; and if he had possessed the means
which the compound salt hyposulphite of soda afforded to subsequent
photographers, of destroying the sensibility of the prepared paper to
further impressions of the rays of light, there can be little doubt
that the invention would have attained a high degree of perfection at
the commencement of the present century. As it was, the failure of Mr.
Wedgwood to accomplish the object he was so nearly attaining appears to
have discouraged attempts by others, and twenty years elapsed without
any advance having been made towards its realization.

M. Niepce, of Chalons on the Saone, who was the first to succeed in
obtaining permanent representations of the images of the camera,
commenced experimenting on the subject in 1814, at least ten years
before M. Daguerre directed his attention to Photography. In 1826
these two gentlemen became acquainted, and conjointly prosecuted
the investigations which led to the beautiful result of the
Daguerreotype. M. Niepce having previously succeeded in obtaining
durable representations of the pictures focused in the camera, he
came to this country in 1827, and exhibited several of the results
of his process, and communicated to the Royal Society an account of
his experiments. These photographs, which may be considered the first
durable ones that had been obtained, were, with one exception, taken
on plates made of pewter. One of the largest was 5¼ inches long and 4
inches wide. It was taken from a print 2½ feet in length, representing
the ruins of an abbey. When seen in a proper light, the impression
appeared very distinct. Another one, which was stated to have been the
first successful attempt, was a view taken from nature, representing
a court-yard. Its size was 7½ inches by 6 inches, but it was not so
distinct as the preceding one. A third specimen was an impression on
paper, _printed from a photograph on metal_, the picture having been
etched into the plate by nitric acid, and then printed from. All these
specimens, though extremely curious as the first successful attempts
to preserve the images of the camera, were more or less imperfect,
and were far from presenting the beautiful results of Photography now
attained. It is remarkable, however, that the original process of
etching the picture on a metal plate, and printing from it, has now, in
the perfected state of the art, become the most recent improvement;
and the prints from photographic plates present some of the most
beautiful effects hitherto produced.[2]

M. Niepce communicated the particulars of his process to M. Daguerre
in December, 1829. They then entered into an agreement to pursue their
investigations jointly, but it was not until ten years afterwards that
the invention of the Daguerreotype by M. Daguerre was made known.
To M. Niepce must, therefore, be awarded the honour of having first
discovered the means of rendering permanent the transient images of
the camera obscura. The plan he adopted was to cover a plate of white
metal with asphalte varnish, and expose it to the action of light in
a camera, when the parts whereon the light was concentrated became
hardened, and the other parts remained unaltered, and could be washed
away.

In M. Niepce's account of the process, after describing the preparation
of the asphalte varnish, he says:--"A tablet of _plated silver_, or
well-cleaned and warm _glass_, is to be highly polished, on which a
thin coating of varnish is to be applied cold, with a light roll of
very soft skin. This will impart to it a fine vermilion colour, and
cover it with a very thin and equal coating. The plate is then placed
on heated iron, which is wrapped round with several folds of paper,
from which, by this method, all moisture has been previously expelled.
When the varnish has ceased to simmer, the plate is withdrawn from the
heat and left to cool and dry in a gentle temperature, and protected
from a damp atmosphere. The plate, thus prepared, may be immediately
subjected to the action of the luminous fluid in the focus of the
camera; but even after having been thus exposed a length of time
sufficient for receiving the impressions of external objects, nothing
is apparent to show that these impressions exist. The forms of the
future picture remain still invisible. The next operation then is to
disengage the shrouded image, and this is accomplished by a solvent."

The solvent employed was a mixture of one part of oil of lavender, and
ten parts of oil of petroleum. The solvent was poured over the plate,
and allowed to remain. M. Niepce continues: "The operator, observing
it by reflected light, begins to perceive the images of the objects
to which it has been exposed gradually unfolding their forms, though
still veiled by the supernatant fluid, continually becoming darker from
saturation with the varnish."

The time required for the exposure of the plates in the camera was six
or eight hours. For the purpose of darkening the pictures, M. Niepce
used iodine, and it has been supposed that the use of iodine for that
purpose suggested the employment of it to his partner.

The process adopted by M. Daguerre was, to deposit a film of iodine on
a highly polished silver plate, by exposing the plate to the vapour
of iodine in a dark box. The prepared plate was then placed in the
camera, and after an exposure of ten minutes or more, according to the
brightness of the day, an impression was made on the iodised silver,
but too faint to be visible. To bring out the image thus invisibly
impressed, the plate was exposed to the vapour of mercury, in a closed
box. The mercury adhered to the parts on which the light had acted,
and left the other parts of the plate untouched; and by this means a
beautiful representation was produced, in which the deposited mercury
represented the lights of the picture, and the polished silver the
shadows. The iodised silver remaining on the plate not acted on by
light, was washed away by a solution of hyposulphite of soda, and the
picture could then be exposed without injury.

Nothing can exceed the delicacy of delineation by such a Daguerreotype;
for the fine surface of the highly polished silver seems to exhibit the
impressions of the smallest objects that emit rays of light. The length
of time required to produce an impression was, however, a serious
obstacle to the use of the process, as originally invented, for taking
portraits. Numerous attempts were consequently made to obtain a more
sensitive material. Bromine was tried, in addition to iodine, and with
such complete success, that a few seconds were sufficient to effect an
impression on the plate, which could be forcibly brought out by the
vapour of mercury.

It was in 1840 that portraits were first taken by the Daguerreotype
process in this country. In the first instance, a concave mirror was
employed to concentrate the rays of light on the plate, instead of a
lens; and the author has now in his possession a portrait taken in
this manner, by "Wolcott's reflecting apparatus." The object of using
a concave mirror was to be able to concentrate a greater number of the
rays of light than could be done by a lens, and thus to form a brighter
image. At the time that portrait was taken, the means had not been
discovered of making the mercury adhere to the plate, and a feather
would brush it away. Soon afterwards, however, M. Fizeau ingeniously
contrived to fix the images on the plate by gilding it. This was done
by pouring on to the plate a few drops of a diluted solution of muriate
of gold, and holding it horizontally over the flame of a spirit lamp;
by which means the gold was deposited and formed a thin, beautiful film
of the metal over the surface, and thus not only made the picture more
durable, but gave it increased effect.

The French government, fully appreciating the importance of the
invention, determined to purchase it from the patentee, and to throw it
open to the public. An account of the invention was published in June,
1839; and in the following month an arrangement was entered into, to
the effect that, in consideration of M. Daguerre making the process
fully known, a pension of 6,000 francs should be granted to him for
life, and a pension of 4,000 francs to M. Isidore Niepce, the nephew of
the original inventor of Photography, his uncle having died before the
final success was attained.

It was generally supposed at the time, that by the grant of those
pensions the invention was thrown open to the whole world, as
represented by the French Minister; but, nevertheless, M. Daguerre
patented the process in other countries, and France alone reaped the
benefit of a free use of the invention.

Whilst M. Daguerre was thus successfully working out to perfection the
plan of producing beautiful naturally-impressed pictures on iodised
silver surfaces, Mr. Fox Talbot was at the same time nearly attaining
the same results. The following is the account given by himself of his
researches:[3]--"Having in the year 1834 discovered the principles of
Photography on paper, I some time afterwards made some experiments on
metal plates; and in 1838 I discovered a method of rendering a silver
plate sensitive to light, by exposing it to iodine vapours. I was at
that time, therefore, treading in the footsteps of M. Daguerre, without
knowing that he, or indeed any other person, was pursuing, or had
commenced or thought of, the art which we now call Photography. But
as I was not aware of the power of mercurial vapour to bring out the
latent impressions, I found my plates of iodised silver deficient in
sensibility, and therefore continued to use in preference my photogenic
drawing paper. This was in 1838. Some time after--in August, 1839--M.
Daguerre published an account of his perfected process, which reached
us during the meeting of the British Association; and I took the
opportunity to lay before the Section the facts which I had myself
ascertained in Metallic Photography."

Whilst to M. Daguerre must be awarded the honour of having first
brought to perfection the method of rendering permanent the images of
the camera on metal plates, Mr. Fox Talbot may claim to be the first
who perfected similar images on paper, which the comparative roughness
of the surface alone prevented from being as delicately beautiful
as the pictures of the Daguerreotype. He commenced his experiments
in Photography in 1834; and on the 31st of January, 1839, he read a
paper before the Royal Society, entitled, "Some Account of the Art of
Photogenic Drawing; or, a process by which natural objects may be made
to delineate themselves without the aid of the artist's pencil."

Mr. Talbot had not then succeeded in obtaining the impressions of
images focused in the camera; what he had succeeded in doing was to fix
upon paper the shadows of objects placed upon it, and exposed to the
light of the sun. The paper was first dipped into a solution of common
salt, and then wiped dry, to diffuse the salt uniformly through the
substance of the paper. A solution of nitrate of silver was then spread
over one surface with a soft brush, and dried carefully before a fire
in a darkened room. The strength of the solution was regulated by first
obtaining a saturated solution of the nitrate of silver, and afterwards
diluting it with six or eight times its volume of water. The objects to
be copied, such as leaves, lace, or other flat surfaces, were pressed
against the prepared paper by a glass fixed in a frame, and exposure
to light quickly darkened all the parts of the paper, excepting those
shaded by the objects. The image thus impressed was what is termed a
"negative," the dark parts which excluded the light being left white on
the paper, and the parts through which the light passed being darkened.
To produce a picture corresponding with the natural lights and shades,
the process was repeated, substituting the picture first obtained, on
thin transparent paper, for the original object, by which means the
lights and shadows were reversed.

The chloride of silver, formed on the surface of the sensitive paper
by the combination of the common salt and nitrate of silver, being
insoluble in water, great difficulty was experienced in washing it
away, so as to prevent the whole surface from afterwards darkening
on exposure to light. The application of hyposulphite of soda, for
the purpose of making the pictures durable, was suggested by Sir John
Herschel, and it answers remarkably well, as it dissolves the chloride
of silver. A solution of ammonia is nearly equally efficacious in
removing the chloride.

The Calotype process, by which the images of the camera can be
fixed upon paper, was invented by Mr. Talbot, in 1840. It is thus
described:--Dissolve 100 grains of crystallized nitrate of silver in 6
ounces of distilled water. Procure some fine writing paper, and wash
one side of it with the solution, laid on with a soft brush; then dry
the paper cautiously, by holding it at a distance from the fire. When
dry, dip the paper into a solution of iodide of potassium, containing
500 grains dissolved in 1 pint of water, and let it remain in the
solution two or three minutes. Then dip it into a vessel of water;
remove the water on the surface by blotting paper, and dry it by a
fire, in the dark or by candle-light. The paper thus prepared is called
"iodised paper;" it is not very sensitive to light, and may be kept for
some time without spoiling. Next dissolve 100 grains of crystallized
nitrate of silver in 2 ounces of distilled water; add to the solution
one-sixth of its volume of strong acetic acid, and call that mixture
A. Then make a strong solution of crystallized gallic acid in cold
water, and let that solution be called B. Mix equal volumes of A and
B together in small quantities at a time. That mixture Mr. Talbot
calls gallo-nitrate of silver, and with it wash over the surface of
the iodised paper. Allow the paper to remain half a minute, and then
dip it into water, and again dry it lightly with blotting paper. The
paper thus prepared is very sensitive, and will receive an impression
in the camera in the shortest possible time. The impression is at first
invisible, but it may be brought out by laying the paper aside in the
dark, or by washing it once more in the gallo-nitrate of silver, and
holding it at a short distance from the fire. To fix the picture, the
paper is first washed in water and lightly dried, and then soaked in
a solution of hyposulphite of soda for a few minutes, by which means
the iodised silver is removed, and after being again washed in water
and dried, the process is completed. The picture thus produced is a
negative one, and requires to be transferred in the manner before
stated. The original Calotype may, by that means, serve to produce a
great number of pictures.

Mr. Talbot's patent was sealed on the 8th of February, 1841. In his
specification, he claimed the use of gallic acid, and he succeeded
in enforcing his claim in a Court of Law, though it appeared that on
the 10th of April, 1839, photographs of objects taken in the solar
microscope in five minutes, by the Rev. J. B. Reade, were shown at
the London institution, which were described to have been produced by
an infusion of galls, and fixed with hyposulphite of soda. It must be
mentioned, however, to Mr. Talbot's honour, that on a representation to
him by the President of the Royal Society that the art of Photography
was impeded in its progress in this country by patent monopolies,
he generously made a present to the public of all his inventions
and discoveries, reserving to himself only the privilege of taking
portraits.

The transfer from one paper to another of the picture obtained in
the camera, and the comparative roughness of the surface of the
paper itself, prevent Calotypes from exhibiting that sharpness and
delicacy of definition which are so admirable in a Daguerreotype.
Several attempts were therefore made to obtain a more smooth surface
for the reception of the image; but without much success, until glass
was adopted for the purpose. To make that material available, it is
necessary to coat it with some substance that will absorb the sensitive
solution. In the first instance, the white of eggs was employed
with considerable success. Albumen has, however, been supplanted by
collodion--a solution of gun-cotton in ether--which is found to be
peculiarly suitable for the reception of the sensitive preparation of
silver.

In conducting the collodion process, the collodion is first iodised by
adding to it iodide of potassium and iodide of silver, dissolved in
alcohol. The iodised collodion is then poured over a plate of glass
that has been carefully cleaned, and is moved about horizontally
until a perfectly uniform film is spread over the surface, to which
it adheres firmly. The plate is afterwards dipped into a solution of
nitrate of silver, which renders it so highly sensitive to impressions
of light, that it will receive an image in less than a second. The
image is latent, until it is developed by pouring over the plate a
mixture of pyro-gallic acid in distilled water, acetic acid, and
nitrate of silver. The impression is fixed with hyposulphite of soda.

The pictures produced by the collodion process are negatives, which
serve admirably for transferring positive pictures on to sensitive
paper. But, if required, the negative picture can be readily changed
into a positive one, by converting the darkened silver into white
metallic silver, by a mixture of protosulphate of iron and pyro-gallic
acid. In a short time a white metallic image is obtained, which, when
relieved by a background of black velvet or black varnish, equals in
delicacy of finish the most beautiful Daguerreotypes.

Many attempts have been made, but hitherto without success, to obtain
photographs coloured, as well as shaded, by nature. The opinions of
those who have most studied the subject differ as to the possibility
of ever attaining that desired object. Sir John Herschel has so far
shown that it is not impossible, as to have impressed the colours of
the solar spectrum on paper, by the mere action of light; and parts
of the images of objects fixed on the screen of the camera are also
sometimes coloured. These facts induce us to hope that in the progress
of discovery some means may be found of obtaining naturally-coloured
photographs, notwithstanding it has been pronounced, by good
authorities, to be an absolute impossibility.

Specimens of coloured photographs were exhibited by Mr. Mercer at the
recent meeting of the British Association, which showed that by the
use of various chemical preparations that are sensitive to light,
photographs may be shaded in colours. The principal re-agents employed
were salts of iron, and by immersing the paper in suitable menstrua,
after the image had been impressed in the camera, the picture was
developed in any colour required; the same tint being spread over the
whole. One purpose to which it was suggested this coloured photographic
process is applicable, is printing on woven fabrics, the action of
light serving as a mordant to fix the colours.

Photography has been already applied to various uses, and it is capable
of being rendered much more valuable. To the meteorologist it affords
the means of registering the rise and fall of the mercury in the
barometer and thermometer, and, by a self-registering apparatus, the
changes of temperature and of atmospheric pressure are marked upon
paper that records the time at which the changes occur. It may also be
applied, in the same manner, to register the directions of the wind,
and the times of its changes. The sun impresses his own image upon
paper; and the spots on his surface, thus correctly delineated, can be
compared with those seen in pictures of the sun at other times; and
the foundation is laid for more correct knowledge of the nature of
those appearances, and of the motion of the sun himself. Photographs of
the moon and planets present exact representations of those heavenly
bodies, as seen through the most powerful telescope; and, with the
assistance of the stereoscope, the figure of the moon is shown in its
true globular form, as it can be seen by no other means. It has been
proposed, indeed, by the aid of Photography, to extend our knowledge
of the stars far beyond the reach of telescopic vision; for as the
image focused on the screen of the camera is composed of rays from
every object on the body of a star, it might be possible to see those
objects by greatly magnifying the image. It remains, however, for the
further progress of discovery and invention, to arrive at so delicate a
delineation by photographic processes, as to obtain landscapes of the
moon, and portraits of the inhabitants of Jupiter!

One of the latest advances in the art of Photography has been the
engraving on steel-plates by the action of light, by which means more
forcible effects have been obtained than by the impressions of light
upon paper. Mr. Fox Talbot has distinguished himself in thus fixing the
images on steel, as he was the first to impress them upon paper. In
his method of doing so, he covers the steel plate with a solution of
isinglass and bichromate of potass, and placing a collodion negative
picture upon it, he exposes it to the action of light. When the picture
is sufficiently impressed, he etches it into the plate by means of
bichloride of platinum. M. Niepce, the nephew of the original inventor
of Photography, has produced the same effect by reviving the first
processes adopted by his uncle; using, as he did, bitumen, dissolved
in essential oil of lavender, to cover the plates. Two other foreign
photographers, M. Poitevin and M. Pretschi, have also successfully
directed their attention to engraving the images of the camera, which
has now obtained a high degree of perfection.

It is well worth notice that these most recent improvements in
Photography are but further developments of the original designs of M.
Niepce, who not only succeeded in etching the pictures impressed by the
light of the sun on his metal tablets, but made use of a glass surface,
on which the now generally adopted collodion process depends.




DISSOLVING VIEWS.


There are no optical illusions more extraordinary than those shown
in the exhibition of Dissolving Views. The effects of the changes in
the diorama are only such as are seen in nature, the same scene being
represented under different circumstances, and the marvel in that case
is that such beautiful and natural effects can be produced on the
same canvas. But Dissolving Views set nature at defiance, and exhibit
metamorphoses as great as can be conceived by the wildest fancy.

Whilst, for instance, the spectator is looking at the interior of a
church, he sees the objects gradually assuming different appearances.
The columns that support the vaulted roof begin to fade away, and their
places are occupied by other forms, which gradually become better
defined and stronger, and a tree, a house, or, it may be, a rock,
thrusts the columns out of view, and the roof dims into blue sky,
chequered with clouds. The original view thus entirely disappears, and
the scene is changed from the interior of a church to open country, or
to a rocky valley. This is done, not by changing at once one scene
into another, but by substituting different individual objects, which
at first appear like faint shadows, and then, becoming more and more
vivid, at length altogether supplant their predecessors on the field of
view, and will, in their turn, be extinguished by others.

It sometimes happens that some strongly marked object resists
apparently the efforts made to dispossess it, and in the midst of a
mountainous scene will be observed the form of a chandelier or of a
statue, that occupied a distinguished place in the church that has
just vanished. In a short time, however, these relics disappear, and
the mountain, the valley, and the lake are freed from the incongruous
images of the former scene.

[Illustration]

[Illustration]

These effects are produced in a manner as simple as they are
extraordinary. All that is requisite is to have two magic lanterns
fitted on to a stand, with their tubes inclined towards each other, so
that both discs of light may exactly coincide, and form on the screen
a single disc. If paintings on glass, representing different views, be
then placed in each lantern, with the lenses adjusted to bring the rays
to a focus on the screen, the two images will be so mingled together
as to present only a confused mixture of colours. Suppose one of the
views to be the interior of a church, and the other to be a mountain
scene;--the pillars of the church will be mingled with trees and rocks,
and in the midst of the confusion there may perhaps be discerned
a strongly painted chandelier or an altar piece. When an opaque
shade is placed before the lens of either of the lanterns, to prevent
the light from reaching the screen, the previous confusion becomes
instantly clear and distinct, and the church or the landscape is seen
without any interfering images. If the opaque screen be gradually
withdrawn from one lens, and at the same time drawn in an equal degree
over the other, the different objects will again be mingled, and those
in the one scene will predominate over those in the other in proportion
to the relative quantities of light permitted to issue from each
lantern to the screen. The two first of the accompanying drawings are
thus blended together in the third, when the screen is half withdrawn
from each.

[Illustration]

It is usual to fix the opaque shade, which alternately covers and
exposes the two magic lanterns, on to a central pin, so that it may be
moved vertically up or down. The shade is so arranged, that in raising
the end to cover the lens of one lantern, the farther end descends,
and exposes, in an equal degree, the other lens. During the time that
either of the views is altogether concealed, the painting is changed;
and in this manner an unlimited number of metamorphoses may be effected.

It requires no expensive apparatus to show the effect of Dissolving
Views on a small scale. Two common magic lanterns are quite sufficient
for the purpose of private exhibition, and the angle at which they
should be fixed on their stand may be readily ascertained after a few
trials. To make the transformation more extraordinary, a man's face may
be painted on one glass and a landscape on the other; and, when the
change is made from the face to the landscape, a strongly painted eye
or nose may be seen occupying the centre of the view, long after the
other features have disappeared, until all the rays of light from that
painting have been excluded. The change from youth to age, from beauty
to ugliness, may also be shown with striking effect.

It will be observed that the principle, on which the metamorphoses
of Dissolving Views depend, is similar to that which produces the
variations in the diorama. In both cases there are two paintings on
the same space, either of which may be shown at pleasure by different
dispositions of the light; the chief difference between them being
that the Dissolving Views are seen altogether by reflected light,
whilst in the diorama the paintings at the back and front are shown
alternately by reflected and by transmitted light.




THE KALEIDOSCOPE.


No invention, on being first brought out, created so general a
sensation as the Kaleidoscope. Every person, who could buy or make one,
had a Kaleidoscope. Men, women, and children--rich and poor; in houses
or walking in the streets; in carriages, or on coaches--were to be seen
looking into the wonder-working tube, admiring the beautiful patterns
it produced, and the magical changes which the least movement of the
glass occasioned.

It was in the year 1814 that Sir David Brewster discovered the
principle on which the effects of the Kaleidoscope depend, whilst
he was engaged in experiments on the polarization of light by
successive reflections between plates of glass. The reflectors were
in some cases inclined to each other, and he remarked the circular
arrangement of the images of a candle round a centre. In afterwards
repeating the experiments of M. Biot on the action of fluids on
light, he placed the fluids in a trough formed by two plates of glass
cemented together at an angle. The eye being placed at one end, some
of the cement which pressed through between the plates appeared to be
arranged in a circular figure. The symmetry of this figure being very
remarkable, Sir David Brewster undertook to investigate the cause of
the phenomenon, and the result of his investigations was the invention
of the instrument to which he gave the name of Kaleidoscope, from the
Greek words καλος {kalos}, beautiful, ειδος {eidos}, a form, and σκοπεω
{skopeô}, to see.[4]

The Kaleidoscope in its simplest form consists of two equal strips of
plate glass, about 8 inches long and 2 inches wide, silvered on one
side, to act as reflectors. These glasses are placed one over the other
exactly, and then the edges on one side being separated, whilst the
two other edges are kept close together, they are fixed by means of
separating pieces of wood and string at the angle required. The glasses
are then fitted into a metal tube, which has an eye-hole at one end,
and at the other end of the tube there is fixed a small cell of ground
glass, to contain pieces of differently stained glass or other objects,
that are to be multiplied by reflections into beautiful symmetrical
figures. In the better kind of Kaleidoscopes, the cell containing the
objects may be turned round, by which means the pieces of glass shift
their positions, and the figures instantly change. The same effect is
produced, though in a less agreeable manner, in the common kind of
instruments, by turning the tube.

To form by the combined reflections from the two glasses a perfectly
symmetrical figure, the sector comprised between the inclined sides of
the glasses may consist of any even aliquot part of a circle. In the
accompanying diagram, the ends of the flat silvered glasses _a c_, _b
c_, are inclined at an angle of 60 degrees; therefore the circle is
completed by the junction of six sectors. In such a Kaleidoscope, the
circular figure will be formed by three reflections from each glass.

[Illustration]

[Illustration]

To make the formation of the circular figure by repeated reflections
more intelligible, we will consider it as composed of the smallest
possible number of equal divisions, as in the second diagram, in which
the circle is divided into quadrants. In such an arrangement of the
reflectors, the figure seen on looking through the central aperture
will consist of four parts. In the first place, the objects included in
the space _a b c_, between the inclined glasses, will be seen directly
by rays of light from the objects themselves; viz., the small cross
_d_, and the triangle _e_. The same field of view will be reflected
from both mirrors, by which reflection the cross on one side will
seem to be doubled, and the triangle on the other will have another
similar one added to it, to make a complete rhomb. The cross will also
be reflected by the mirror on the right side, and the triangle by the
one on the left. The images of the objects contained within the space
_a b c_, being thus presented by reflection on both sides, they become
the objects for further reflections from parts of the mirrors still
nearer the spectator. Thus the images _d_¹ on both sides are reflected
to form the single image _d_², and the images _e_¹ are in the same
manner reflected to form the second image _e_².

When the angle formed by the inclination of the mirrors divides the
circle into a greater number of sectors, the reflections of the images
are repeated, from points nearer and nearer to the eye, and the circle
is thus completed, however numerous the sectors may be; but at each
repetition of the reflection, the images will become more dim, since,
owing to the imperfection of reflecting surfaces, a portion of the
light is absorbed at each reflection.

In the first instruments that were constructed, the objects were
fixed in the field of view, therefore scarcely any change of pattern
was obtainable. It was not until some time afterwards that the idea
occurred to Sir David Brewster of producing endless changes of the
figures, by making the objects movable in a cell of glass at the end
of the instrument. He afterwards introduced other improvements in the
Kaleidoscope, for extending its range of objects, for varying the
angles of inclination, and for projecting the figures on a screen. In
the instrument, as ordinarily made, the objects to be seen properly
must be placed close to the end of the reflectors; but by the addition
to the instrument of a tube containing a lens, the rays from distant
objects are brought to a focus near the mirrors, and the image formed
there is repeated by the reflectors in the same manner as a solid
object.

The projection of the figures on a screen, by an apparatus similar to
a magic lantern, gives great additional pleasure to the effects of
the Kaleidoscope, as the figures are not only seen by several persons
at the same time, but they are presented in a magnified form. The
projection of the figures also increases the use of the instrument in
designing patterns, for which purpose it has been employed with great
advantage.

A patent for the Kaleidoscope was taken out in 1817, but the high
prices charged by the opticians who were authorized by the inventor
to sell the instrument, and the facility with which it could be
made, occasioned a general violation of the patent right, and it was
not long before the claim of Sir David Brewster, as the original
inventor, was disputed. In the indignant vindication of his claim, he
observes:--"There never was a popular invention which the labours of
envious individuals did not attempt to trace to some remote period;"
and the Kaleidoscope was not an exception. It was found that Kircher
had described the effects of repeated reflections as far back as
1630; and that Mr. Bradley had, in 1717, made a philosophical toy,
consisting of two small mirrors, that opened like a book, which, when
partially opened, repeated the reflections of objects placed near it
in the same manner as the Kaleidoscope. But this instrument was so
different in its construction, and in the effects it produced, from the
Kaleidoscope, that Sir David Brewster's claim to be the inventor may
be freely admitted. The fact that it took the world by surprise, and
created a sensation greater than any other invention had done before,
is sufficient to establish its title as an original invention.




THE MAGIC DISC.


There are several ways of illustrating the retention by the retina of
the eye of the images of objects after they have been withdrawn from
sight, but none is so curious as the philosophical toy called the Magic
Disc, which, from the optical principles involved in its extraordinary
effects, deserves to be noticed as one of the remarkable inventions of
the present century.

One of the most striking methods of exhibiting the retentive property
of the retina, before the invention of the Magic Disc, was to paint
different objects at the back and on the front of a card, and by then
giving rapid rotation to the card, both objects were seen together.
Thus, when the figure of a bird is painted on one side, and an empty
cage on the other, by rapidly turning the card, the bird appears to be
in the cage. In the Magic Disc the objects are painted on the same side
of a circular piece of card-board, and both are exposed to view during
their rapid rotation.

The disc is divided into eight or ten compartments, in each one of
which the same figures are repeated, though the positions of one
or more of them are changed. A favourite subject represented is a
clown leaping over the back of a pantaloon, which affords a simple
illustration of the apparent relative movements of two bodies, and will
serve to explain how the effect is produced.

[Illustration]

The instrument consists of a disc of stiff card-board, about nine
inches diameter, mounted on a horizontal pivot in the centre, on which
it may be freely turned. Between each of the compartments of the disc
there is an elongated aperture, about one inch long and a quarter of an
inch wide, for the eye to look through. Suppose the disc to be divided
into eight compartments, by radial lines. In the compartment No. 1,
the pantaloon is represented in a stooping posture, and the clown is
on the ground ready to make a spring. In No. 2 the pantaloon is in the
same attitude, but the clown has commenced his leap, and is raised a
little way from the ground. In the third division he is shown still
higher in the air; and in the fourth he is mounted above the shoulders
of pantaloon, who retains the same posture as at first. The fifth
compartment represents the clown as having jumped over pantaloon's
head, and coming down to the ground; and in each succeeding division
his farther descent is shown, till, in No. 8, he has reached the ground
again, and is ready to recommence the leap.

When the disc is turned rapidly round on its pivot, the figures
painted upon it are mingled together, and present a confused medley of
lines and colours, in which no object can be distinctly defined. This
mingling of the objects is caused by the retention of the images by the
retina, so that if the eye be directed to any point, the impression of
the lines and colours that pass rapidly before it is not effaced before
another and another appear to produce fresh impressions, and they
mingle together in confusion. If, for instance, there were a circle
formed of dots marked on the disc, the impression of each dot on the
retina would be prolonged; and as, by the rotation, other dots would
come into the field of view before the impression of the first was
removed, it would form an unbroken ring. But if the disc were screened
from sight, at intervals of nearly equal duration to that of the
continuous impression, so as to efface the image of one dot before the
rays of another were admitted to the eye, then the ring would be seen
to be composed of dots, as distinctly as when the disc was stationary.

The effect of screening the objects from the eye at short intervals
is produced by looking with one eye through the openings at the image
of the disc, reflected from a mirror. The figures are then seen only
when the apertures come opposite the eye; but as the impression of one
view remains till it is renewed by the light admitted through the next
aperture, there is continuous vision of the objects painted on the disc.

It is thus that the figures of pantaloon and clown become visible, and
their apparent relative movements are occasioned. For instance; each
time that the impression of the figure of the pantaloon is renewed,
he is seen in the same place and in the same attitude; therefore he
appears to be stationary, though the successive pictures that compose
his figure to the eye are in rapid rotary motion. The figure of the
clown, however, is seen in a different position each time that he
comes into view, therefore he appears to be in motion relatively to
pantaloon, though stationary as regards his absolute position on the
disc.

The same effect would be produced if the disc, during its rotation,
were seen by successive electric sparks. The electric spark is so
momentary in its duration, that the most rapidly moving objects appear
stationary; therefore each spark would show a seemingly stationary
disc, on which the figure of the clown would appear in different
relative positions; and the illusion would be as perfect as when the
rays of light are interrupted at intervals.

The electric spark is so instantaneous that a cannon ball might be
seen in its rapid flight, if illuminated by a flash of lightning, and
would seem to be stationary. Professor Faraday mentioned, in one of his
lectures, the extraordinary appearance which a man, who was jumping
over a stile, presented when seen by lightning on a dark night. The man
seemed to be resting horizontally in the air, with one hand touching
the stile.

The duration of the impression of an object on the retina is capable of
illustration by means of the Magic Disc in a great variety of designs,
each one of which may represent many movements. The turning of the
wheels of machinery, the tossing of balls, the dancing figures of men
and women may thus be shown, the designs for which afford ample scope
for exercising the pencil of an ingenious artist.




THE DIORAMA.


Those who are old enough to remember the Regent's Park before there
were any houses northward of the New Road, may recollect that among
the first buildings erected, on what is now called Park Square, was a
strange-looking, partly semi-circular erection, provided with ample
lighting space, which attracted great attention during its progress,
and was the cause of much speculation as to its probable purpose. That
building was intended for the exhibition of the Diorama.

M. Daguerre, the inventor of the Daguerreotype, had, in conjunction
with M. Bouton, a short time previously opened a similar exhibition in
Paris, where the beauty of the paintings, aided by the extraordinary
effects of newly contrived dispositions of the light, had excited
a great sensation. The Diorama was opened in London on the 6th of
October, 1823, and for a long time it was equally popular in this
metropolis.

The visitors, after passing through a gloomy anteroom, were ushered
into a circular chamber, apparently quite dark. One or two small
shrouded lamps placed on the floor served dimly to light the way
to a few descending steps, and the voice of an invisible guide gave
directions to walk forward. The eye soon became sufficiently accustomed
to the darkness to distinguish the objects around, and to perceive
that there were several persons seated on benches opposite an open
space, resembling a large window. Through the window was seen the
interior of a cathedral, undergoing partial repair, with the figures
of two or three workmen resting from their labour. The pillars, the
arches, the stone floor and steps, stained with damp, and the planks
of wood strewn on the ground, all seemed to stand out in bold relief,
so solidly as not to admit a doubt of their substantiality, whilst the
floor extended to the distant pillars, temptingly inviting the tread
of exploring footsteps. Few could be persuaded that what they saw was
a mere painting on a flat surface. This impression was strengthened
by perceiving the light and shadows change, as if clouds were passing
over the sun, the rays of which occasionally shone through the
painted windows, casting coloured shadows on the floor. Then shortly
the brightness would disappear, and the former gloom again obscure
the objects that had been momentarily illuminated. The illusion was
rendered more perfect by the excellence of the painting, and by the
sensitive condition of the eye in the darkness of the surrounding
chamber. Whilst gazing in wrapt admiration at the architectural
beauties of the cathedral, the spectator's attention was disturbed by
sounds underground. He became conscious that the scene before him was
slowly moving away, and he obtained a glimpse of another and very
different prospect, which gradually advanced until it was completely
developed, and the cathedral had disappeared. What he now saw was a
valley, surrounded by high mountains capped with snow. This mountain
valley seemed scarcely less real than the arched roof and columns of
the cathedral, whilst a foaming cascade, dashing down the rocks, and
the sound of rushing waters, added to the illusion. After looking for
some time at this beautiful valley, the clouds were seen to gather on
the mountain tops, and a storm impended. A gleam of sun-light, still
resting on the edge of the clouds, exhibited a strange contrast between
the silvery brightness and the dense black vapour that shrouded the
hills, and could almost be felt. It was but a passing thunderstorm.
Presently the dark clouds rose from the valley, and dispersed; the sun
again shone on cottage, vineyard, and mountain, charming the spectator
as much by the beauty of the scene as he was astonished by the
wonderful change.

Such was the Diorama as it was first exhibited in London to admiring
crowds. In subsequent years greater changes were made in the variations
of light and shade; and by the introduction of mechanical contrivances,
with more or less success, the magical effects were increased, without,
however, adding to the apparent reality of the objects. A church or
cathedral was always the subject of one view, and sometimes of both.
The interior of an empty church would be shown by evening twilight.
The shades of evening gradually darkened into the obscurity of
night, and then the glimmer of candles would be seen spreading more
and more widely, until the church was lighted up, and it was occupied
by a crowded congregation at midnight mass. Some views represented
the exterior of a ruin or of a cathedral after sunset, and as night
advanced, the stars twinkled in the blue sky, and the moon rose and
threw its silvery light on water, buildings, and clouds, contrasting
in some cases with the red glare of lamps from the windows of houses
and shops. The disc of the moon exactly resembled that of the real
luminary, and all around being so dark, the rays from its surface cast
shadows of intervening objects. In one picture a still more astonishing
appearance was produced, by the change of the interior of a beautifully
painted and decorated church into a mass of charred ruins.

The means principally adopted for the production of these magical
changes in a painting on a flat surface, and for giving such seeming
reality to the objects represented, were for some time kept secret;
nor do we think they are even yet much known. As in many other clever
inventions, the effects are produced in a very simple manner. The
picture is painted on both sides of a transparent screen, and the
change of scene is occasioned almost entirely by exhibiting the picture
at one time by reflected light, from the surface nearest the spectator,
and afterwards by transmitted light, after excluding the light from the
front.

Let us take for illustration the interior of a church, at first seen
empty, and afterwards filled with people, and illuminated by candles.
The empty church is painted on the front on fine canvas or silk, in
transparent colours, and at the back are the figures and candles,
and other objects intended to appear with them. The arrangements for
illuminating the picture are so contrived, that the light may be thrown
entirely on the front or on the back, or partly on both. When the light
is on the front, the empty church only is visible. It is then gradually
darkened, and the back of the picture is illuminated, by which means
the figures and candles are seen; and the form of the building being
preserved, the same church, which was before empty, becomes occupied by
a crowded congregation.

It may be mentioned, as an illustration of the perfect illusion of
the Diorama, that a lady who on one occasion accompanied the author
to the exhibition, was so fully convinced that the church represented
was real, that she asked to be conducted down the steps to walk in the
building.

[Illustration]

The effect of changing the direction of the light may be readily
perceived by making a drawing on both sides of a sheet of paper, as
shown in the annexed engraving. The side backing this page represents
the interior of St. Paul's Cathedral when empty, and on the back
several figures are drawn. Those figures are invisible until the
leaf is held up against the light, and when the drawing is seen as a
transparency, the objects on the back, as well as those in front, come
into view, and the building appears to be occupied.

[Illustration]

Any one who has a taste for drawing, and a little ingenuity, may thus
produce many pleasing and astonishing effects. It will be desirable
to procure, in the first instance, a box, so contrived that it will
hold the painting, and afford the means of throwing the light on the
front or on the back at pleasure. The diagram shows the form of such
a box. The letters _a_, _b_, _c_, _d_ mark the outside; the aperture,
at _c d_, being enlarged to permit several persons to look into it at
the same time. The box may be of any required dimensions, to suit the
size of the drawing, which is to be fitted into a groove at _a b_,
and the interior must be blackened. The lid, _e_, when open, as in
the diagram, admits the light to the front of the picture, the back
being covered with an opaque screen. As the lid is closed, the picture
becomes darkened, and by the gradual removal of the screen at the same
time, it is changed into a transparency. This portable Diorama can be
most conveniently shown by lamplight, the flame of an argand lamp, the
wick of which can be heightened and lowered, being best adapted for
the purpose. The effect by daylight is, however, superior, but the
room must then be darkened, and the admission of light confined to the
picture.

[Illustration]

The moving water, and the motion of smoke and clouds, which were
frequently introduced in the Diorama, were mechanical additions, the
effects being produced by giving motion to bodies behind, the forms
of which were seen by transmitted light. The introduction of such
mechanical aids, however, detract from the artistic character of the
Diorama, the principal merit of which consists in exhibiting the
changes occasioned by variations in the mode of throwing the light on
the two-faced picture.

It is to be regretted that exhibitions of a larger and more showy kind
should have superseded the Diorama in public estimation; and that,
from the want of support, their charming and marvellous pictorial
representations, which formed, in days gone by, one of the principal
"sights" of London, should be now closed.




THE STEREOSCOPE.


One of the most beautiful as well as the most remarkable pictorial
illusions is produced by the combination of two views into one by the
recently invented instrument called the Stereoscope. In the Diorama, in
the Magic Disc, and in the Dissolving Views, separate paintings combine
to produce different effects; but in the Stereoscope the two pictures
unite into one to give additional effect to the same view, and to make
that which is a flat surface, when seen singly, appear to project like
a solid body.

The principle of the Stereoscope depends on the different appearance
which near objects present when seen by the right or by the left eye.
For instance, on looking at a book placed edgewise, with the right eye,
the back and one side of the book will be perceived; and on closing
the right eye and opening the left, the back and the other side of the
book will be seen, and the right-hand side will be invisible. It is the
combination of both these views by vision with two eyes that produces
the impression of solidity of objects on the mind; and if the different
appearances which the book presents to each eye be copied in separate
drawings, and they can afterwards be placed in such a position as to
form a united image on the retinæ of the eyes, the same effect is
produced as if the book itself were looked upon.

[Illustration]

This diagram represents the outlines of a near object, as seen by each
eye separately. The one on the right hand shows it as seen with the
right eye, and the other as it looks with the left eye; and if both
drawings be combined into one image, it stands out in bold relief.
This may be done without any instrument, by squinting at them; but
the effect is more readily and far more agreeably produced by the
Stereoscope, so named from the Greek words στερος {steros}, solid, and
σκοπεω {skopeô}, to see.

Professor Wheatstone claims to be the first who contrived an instrument
to illustrate this effect of binocular vision, and he also claims to be
the first who brought to notice the different appearances of objects
seen with each eye separately. Sir David Brewster, however, disputes,
on behalf of Mr. Elliot, of Edinburgh, Professor Wheatstone's claim to
the invention of the first stereoscopic instrument; and he has shown
that the difference of vision with each eye was remarked by Galen,
1,700 years ago; that it was noticed by Leonardo da Vinci in 1500, and
formed the subject of a treatise by a Jesuit, named Francis Aquilonius,
in 1613; and that it was a well-known phenomenon of vision long before
it was mentioned by Professor Wheatstone.[5] Mr. Elliot, though he
conceived the idea, in 1834, of constructing an instrument for uniting
two dissimilar pictures, did not carry it into effect until 1839, the
year after Mr. Wheatstone had exhibited his reflecting Stereoscope to
the Royal Society, and at the meeting of the British Association.

Mr. Elliot's contrivance, to which Sir David Brewster is inclined to
give precedence in point of date, was very inferior in its effects
to the reflecting Stereoscope. It was without lenses or mirrors, and
consisted of a wooden box 18 inches long, 7 inches broad, and 4½ deep,
and at the end of it was placed the dissimilar pictures, as seen by
each eye, that were to be united into one. The view he drew for the
purpose comprised the moon, a cross, and the stump of a tree, at
different distances; and when looked at in the box, the cross and the
stump of the tree appeared to stand out in relief.

The accompanying woodcut represents the original stereoscopic pictures,
copied from Sir David Brewster's book; and by looking towards the
picture on the left with the right eye, and on the right-hand picture
with the left eye, the two will be seen united, and the cross and the
stump of the tree will appear to stand out solidly.

[Illustration]

The arrangement of the apparatus, as described by Professor Wheatstone,
in his paper read before the Royal Society, consists of two plane
mirrors, about 4 inches square, placed at right angles; and the
drawings, made on separate pieces of paper, were reflected to the eyes
looking into the mirrors at their junction. The diagram is a sketch of
this arrangement. In the middle of a narrow slip of wood, _d e_, about
12 inches long, the two mirrors, _a b_, are fixed, inclined at the
required angle from their line of junction at _c_. Upright pieces of
wood, _d h_, _e f_, at each end, are furnished with slides or clips to
hold the drawings, which are reflected from the inclined mirrors, and
seen in them by each eye separately. Thus, the left eye sees only the
picture fixed on _d h_, and the right eye sees the one placed at _e f_;
and the two images, being combined at the seat of vision, produce the
same impression as a solid body.

[Illustration]

It is almost unnecessary to describe the external appearance of the
lenticular instrument invented by Sir David Brewster, and explained by
him at the meeting of the British Association in 1849. In the best kind
of instruments the glasses, through which the pictures are seen, are
composed of a single large double-convex lens, divided in the middle,
the thin edges being set towards each other, about 2½ inches apart. The
more improved instruments, indeed, are made from lenses upwards of 3
inches in diameter, which, being cut into two, and the thin parts being
ground flat, are set edge to edge, and from an aperture sufficiently
large for both eyes to look through. By this means the instrument
suits all eyes, without requiring adjustment, and the field of view is
increased. A diaphragm, or partition, placed at the junction of the two
lenses, confines the vision of each eye to its appropriated picture,
and thus tends to prevent the confusion of images that might otherwise
arise.

The object of using semi-lenses is to facilitate the union of the two
pictures into one, by looking through the lens towards its edge,
instead of through the centre, the image being thus refracted to a
different position. This may be easily exemplified by looking at an
object steadily through different parts of the same lens. After looking
at it with the right eye through the centre, and whilst keeping the
axis of the eye in the same direction, move the lens slowly towards the
right, so as to bring the edge of the lens opposite the pupil. This
movement of the lens towards the right hand will be accompanied by an
apparent movement of the image towards the left, so as to bring it to a
point between the two eyes. If the experiment be repeated with the left
eye, the image will be removed towards the right hand; and thus, by
looking at the two stereoscopic pictures through the thin parts of two
lenses, the images are superposed and form a single one.

Sir David Brewster attached much importance to the semi-lenses, which
have the effect of prisms in refracting the rays of light; but that
form of lens is not essential to give apparent solidity to the images;
and many of the commoner kind of instruments are now made with ordinary
double-convex lenses, and without any partition. With the semi-lens,
however, there is less difficulty in uniting the two pictures into one
than when an ordinary lens is employed.

In taking photographic pictures for the Stereoscope with a single
camera, it is necessary to alter the angle of the instrument after
having taken one picture, to direct it to the same object in the
angle of vision as seen by the other eye. This method of producing
stereoscopic pictures with the same camera is very objectionable when
any moving objects are in the field; for they will be in a different
position in each, and sometimes disappear altogether from the second
picture. The plan adopted by the best photographers is to have two
cameras set at the requisite angle to each other, so that both pictures
or portraits may be taken at the same time.

At the meeting of the British Association in 1853, M. Claudet
endeavoured to establish some rules for the angle at which photographic
pictures must be taken, in order to produce the best effect of relief
and distance without exaggeration. He observed, that in looking at a
single picture with two eyes, there is less relief and less distance
than when looking at it with one eye, because in the latter case we
have the same effect we are accustomed to feel when we look at the
natural objects with one eye; while, if we look at the single picture
with two eyes, we have on the two retinæ the same image with the same
perspective, which is not natural, and the eyes have not to make the
usual effort for altering their convergence according to the plane on
which the object observed is situated. This inaction of the convergence
of the eyes diminishes the illusion of the picture, because the same
convergence for all the objects represented gives an idea that they
are all placed on the same plane. The photographic image being the
representation of two different perspectives, we must, when we look
at them in the Stereoscope, as when looking at the natural objects
themselves, converge, more or less, the axes of the eyes. Therefore
we make the same effort, and have the same sensation in regarding
the combined photographic pictures, as when we look at the objects
represented.

Sir David Brewster has suggested various applications of the
Stereoscope; viz., to painting, to sculpture and engineering, to
natural history, to education, and to purposes of amusement. The latter
is the principal purpose to which the instrument is at present applied;
and some of the many ways in which it may contribute to delight the
spectator are pointed out in Sir David Brewster's book.

"For the purpose of amusement," he observes, "the photographer might
carry us even into the regions of the supernatural. His art enables
him to give a spiritual appearance to one or more of his figures,
and to exhibit them as 'thin air,' amid the solid realities of the
stereoscopic picture. While a party are engaged with their whist or
their gossip, a female figure appears in the midst of them with all the
attributes of the supernatural. Her form is transparent; every object
or person beyond her being seen in shadowy but distinct outline. She
may occupy more than one place in the scene, and different portions
of the group might be made to gaze upon one or other of the visions
before them. In order to produce such a scene, the parties which are
to compose the group must have their portraits nearly finished in the
binocular camera, in the attitude which they may be supposed to assume
if the vision were real. When the party have nearly sat the proper
length of time, the female figure, suitably attired, walks quickly to
the place assigned to her, and after standing a few seconds in the
proper attitude, retires quickly, or takes as quickly a second, or even
a third, place in the picture, if it is required, in each of which she
remains a few seconds, so that her picture in these different positions
may be taken with sufficient distinctness in the negative photograph.
If these operations have been well performed, all the objects
immediately behind the female figure, having been previous to her
introduction impressed upon the negative surface, will be seen through
her, and she will have the appearance of an aërial personage, unlike
the other figures in the picture."

It is in the foregoing manner that the remarkable stereoscopic effect
of "Sir David Brewster's ghost" is produced, a representation of which
is given in the next page.

Sir David Brewster mentions many other curious applications of the
Stereoscope, among which are the dioramic effects of pictures seen
alternately by reflected and by transmitted light; a daylight view
being apparently lighted up artificially in the night, by seeing it at
one time with the light reflected from the surface, and then excluding
the light from the front, and viewing it as a transparency.

One of the most interesting effects of the Stereoscope has been
recently produced by Mr. De la Rue, who has contrived the means of
giving apparent rotundity to the surface of the moon, as viewed
through a powerful telescope. The disc of the full moon, however
highly magnified, presents, as is well-known, the appearance of a flat
surface, with the lights and shadows marked seemingly on a plane.
Owing to the great distance of that luminary, there is no variation
in its appearance, whether it be looked at with one eye or with the
other, therefore it seems removed beyond the operation of the ordinary
cause of stereoscopic effects. Nevertheless, Mr. De la Rue has taken
photographs of the moon which, when placed in the Stereoscope, combine
to form a solid-looking globe, on which all the lights and shadows are
distinctly and beautifully delineated. He has produced this effect by
taking his photographs at different periods of the year, when there is
a slight variation in the direction of the moon's face to the earth;
and by combining these separate photographs into one image in the
Stereoscope, the form of the moon appears as convex as the surface of
an artificial globe.

[Illustration]

M. Claudet, who is one of the most successful photographers in
the metropolis, has contrived an arrangement which he calls a
"Stereomonoscope," by which the appearance of solidity is communicated
to a single image formed on a screen of ground glass. The screen of
ground glass has a black back, and is placed in the focus of a lens in
an ordinary camera obscura, wherein the image may be seen by looking
down upon it. The particles of the roughened glass reflect to each
eye different parts of the image focused on the screen, and by this
means a similar effect is produced as when two dissimilar pictures are
looked at through a stereoscope instrument. One great advantage of this
arrangement is that several persons may look at the image at the same
time.

Mr. John Sang, of Kirkaldy, has very recently imparted stereoscopic
effect to copies of paintings and engravings, the flat surfaces of
which were previously thought to defy any such application of the
Stereoscope. The means he employs of doing so are at present kept
secret, but he has shown its practicability by copying, on wood
engravings, Mr. George Cruikshank's series of "The Bottle." In some
respects this process seems almost more wonderful than the original
Stereoscope, for it gives solid form and apparent substantiality to the
mere creations of the artist's pencil.




THE ELECTRIC TELEGRAPH.


No application of science has so completely realized the visions of
fancy as the Electric Telegraph. So closely, indeed, does the real of
the present day approach to the ideal of ages past, that it might be
supposed the narratives in the tales of faëry land were true records
of the inventions of former times, and that the combined efforts of
inventive genius during the last half century were but imitations and
reproductions of what had been successfully accomplished "once upon a
time." There is also an intermediate period--between the indefinite
of faëry tales and the positive of scientific history--in which
sympathetic tablets and magical loadstones, scarcely less mythical, are
stated to have been invented; and the individuals are named who thus
paved the way for instantaneous communication between all parts of the
world.

The Jesuits of the sixteenth and seventeenth centuries took the
place of the magicians of the Middle Ages. In the seclusion of their
monasteries, they speculated on the mysterious powers of Nature, then
partially revealed to them, and shadowed forth images of their possible
applications. It is to a vague speculation of this kind that we may
attribute the notice given by Strada, in his "Prolusiones Academicæ,"
of the sympathetic magnetic needles, by which two friends at a distance
were able to communicate; though the then fanciful idea has been
literally realized. A still more extraordinary foreshadowing of one
of the most recent improvements of the Electric Telegraph was the
transference of written letters from one place to another by electric
agency. This is said to have been accomplished by Kircher, who, in his
"Prolusiones Magneticæ," describes, though very vaguely, the mode of
operation. But even admitting that there were substantial foundations
for these imaginary phantasms, that would not in the least detract from
the merit of those who, following closely the footsteps of scientific
discovery, have successfully applied the principles unfolded by the
investigations of others, and by their own assiduous researches. Thus,
whilst steam navigation was facilitating the means of intercourse over
rivers and seas, and whilst railways and locomotive engines served to
bring distant cities within a few hours' journey of each other, another
source of power, infinitely more rapid in its action than steam, has
been made to transmit intelligence from place to place, and from one
country to another, with the speed of lightning.

The plan of making communications by signals has been in operation from
time immemorial; the beacon lights on hills having served in ancient
as well as in modern times to give warning of danger, or to announce
tidings of joy. Such simple signals were not capable of much variety of
expression; but even beacon lights might be made to indicate different
kinds of intelligence, by multiplying the number of the fires, and
by altering their relative positions. It was not, however, till the
invention of telegraphs that anything approaching to the means of
holding regular communication by signals was attained. The semaphore
of the brothers Chappe, of France, invented by them in 1794, was the
most perfect instrument of the kind, and was generally employed for
telegraphic purposes, until it was supplanted by the Electric Telegraph.

The semaphore consisted of an upright post, having arms on each side,
that could be readily extended, at any given angle. The extension of
these arms on one side or the other, either separately or together,
and at different angles, constituted a variety of signals sufficient
for the purposes of communication. The semaphores, erected on elevated
points, so as to be visible through telescopes, signalled intelligence
slowly from one station to another, till it reached its ultimate
destination; and thus--daylight and clear weather permitting--brief
orders could be sent from the Admiralty to Portsmouth in the course of
a few minutes. But the communication was liable to be interrupted by
fogs, as well as by nightfall.

A remarkable instance of the imperfection of sight telegraphs occurred
during the Peninsular War. A telegraphic despatch, received at the
Admiralty from Portsmouth, announced--"Lord Wellington defeated;"--and
then the communication was interrupted by a fog. This telegraphic
message caused great consternation, and the utmost anxiety was
experienced to learn the extent of the supposed disaster. When,
however, the fog dispersed, the remainder of the message gave a
completely opposite character to the news, which in its completed form
ran thus: "Lord Wellington defeated the French," &c.

Some better means of transmitting important intelligence was evidently
wanted; for not only was the semaphore liable to frequent interruptions
by the weather, but its action was very slow, and the frequent
repetitions from station to station increased the risk of blunders.

The instantaneous transmission of an electric shock suggested the
means of communicating with greatly increased rapidity; and when
it was ascertained, by experiments made by Dr. Watson at Shooter's
Hill, in 1747, that the charge of a Leyden jar could be sent through
a circuit of four miles, with velocity too great to be appreciable,
the practicability of applying electricity for conveying intelligence
became at once apparent.

Of the many means by which this object was attempted to be
accomplished, it will be only possible, in this general survey, to
notice those that mark the first steps of the invention, and the most
important of those that have accompanied its progress to the present
time.

The first method that suggested itself was to transmit signals by
means of pith-ball electrometers. When, for instance, two pith-balls
are suspended from a wire that is made to form part of an electric
circuit, the electricity communicated to the balls causes them to
diverge, and when the electricity in the wire is discharged, they
immediately collapse. This action of pith-balls, when electrified,
was the simplest mode known of making telegraphic signals, and it was
accordingly adopted by several of the early inventors of Electric
Telegraphs. The first person who proposed to apply it for that purpose
was M. Lesage, of Geneva, in 1774. His plan was to form 24 electric
circuits by as many separate wires, insulated from each other in glass
tubes; and to place in the circuit, at each communicating station,
an equal number of pith-ball electrometers. Each electrometer was to
represent a letter of the alphabet, and they were to be brought into
action by an excited glass rod. When a communication was to be made,
the wires connected with the separate galvanometers were to be charged
alternately with electricity by the excited rod of glass; and the
person at the receiving station, by noticing which of the electrometers
were successively put into action, could spell the words intended to be
communicated.

By the means thus proposed, correspondence could have taken place at
only short distances, for the charge of an excited glass rod would have
been too feeble to produce any sensible effect on the electrometers had
the length of the circuit been considerable. This difficulty might
have been overcome by substituting the charge of a Leyden jar for the
excited glass; but the more serious obstacle to the use of such a
telegraph would have been the cost, and the difficulty of insulating
the 24 wires required to work it.

Most of the early telegraphic inventors encumbered their inventions
with the same obstacle, as they seemed to consider it necessary to
have a separate circuit for each letter of the alphabet. It was not so
however, with all; for M. Lomond, a Frenchman, who ranks second in the
list of telegraphic inventors, modified the principle of M. Lesage, so
as to enable him to work with only two wires and one electrometer at
each station. With the experience since gained in the application of
the needle telegraph, such an arrangement seems very simple, and we are
inclined to wonder that it was not generally adopted, especially after
M. Lomond had shown the way.

To produce all the requisite signals with a single pith-ball
electrometer, it was necessary to vary the durations of each
divergence, and to combine several to form a single symbol. Thus,
suppose that a single divergence of the pith-balls for a second was
understood to signify the letter _A_; one divergence, followed by an
immediate collapse, by discharging the electricity, might signify _B_;
two prolonged divergences might signify _C_, and two short ones _D_;
and by thus increasing the number and varying the divergences of the
two pith-balls, all the letters of the alphabet might be indicated.

A still more direct method of representing the letters of the alphabet
was proposed by M. Reizen in 1794, by the application of the means
frequently adopted for exhibiting the light of the electric spark. The
charge of a Leyden jar was sent through strips of tin foil, pasted on
to a flat piece of glass, so as to form several lines, joined at the
ends alternately into a continuous circuit. Interruptions were made
in the foil by cutting small portions away, at which points brilliant
sparks appeared when the jar was discharged. As the interruptions
were so contrived as to form letters, and the strips of tin foil were
all arranged separately on a long pane of glass, any letter required
could be distinctly made visible by discharging the jar through that
particular circuit. To produce all the letters of the alphabet in this
manner, a separate circuit was required for each.

Another plan, far less feasible, and scarcely deserving of notice,
excepting for its peculiarity, was proposed in the following year
by M. Cavallo, who suggested the setting fire to combustibles, or
the explosion of detonating substances, as the means of signalling
intelligence. About the same time several attempts were made by
electricians in Spain to transmit signals by electricity, but their
plans were not more practicable than those already mentioned, and
depended for their effects on the discharge of Leyden jars.

The discovery of voltaic electricity at the beginning of the present
century was an important step in the progress of the Electric
Telegraph, though several years elapsed before the applicability of
the discovery for that purpose became known; and it was not fully
appreciated till within the last twenty years.

The electricity generated by the voltaic battery is far greater in
quantity than the most powerful electrical machine can excite, whilst
its intensity is so feeble that it cannot pass in a spark through the
smallest interval of air. It presents, therefore, much less difficulty
in the insulation of the wires than frictional electricity, whilst
the rapidity of its transmission is for practical purposes equally
efficient. The electricity generated by the voltaic battery being great
in quantity and feeble in intensity, it is capable also of effecting
chemical decomposition and of imparting magnetism, both of which
properties have proved eminently useful in perfecting the Electric
Telegraph.

The first application of voltaic electricity to telegraphic purposes
was made by Mr. Soemmering in 1809. The signals of his telegraph
consisted of the bubbles of gas arising from the decomposition of
water, during the action of the electric current. His apparatus
consisted of a small glass trough, filled with acidulated water,
through the bottom part of which were introduced several gold wires
corresponding to the letters of the alphabet. The instant that an
electric current was sent through any two of the wires, by making
connection with a voltaic battery at the transmitting instrument,
bubbles of hydrogen gas rose from one of the gold wires, and bubbles of
oxygen gas from another; and as the volume of hydrogen gas, liberated
during the decomposition of water, exceeds by sixteen times that of
the oxygen, it was easy to distinguish them. In this manner all the
letters of the alphabet could be indicated by using 24 wires. The
object of having gold wires in the decomposing trough was to prevent
the oxidation of the metal; for had copper, or any other metal that
combines with oxygen, been employed, the points of the wires would soon
have become corroded.

This telegraph of Soemmering's, though not adapted for practical
application in the form he presented it, on account of the number of
wires required for the purpose, was nevertheless superior to any that
had previously been invented; and by a little modification it might
have been made a perfect instrument, capable of transmitting messages
by means of only two wires. Such a modification of the instrument was
proposed by M. Schweigger, twenty years afterwards; the only thing
required being the adoption of a code of symbols, by means of which
all the letters might be indicated by combinations of the four primary
signals that are obtainable by two wires, as is at present done by the
needle telegraph in common use. At that time, however, the discovery of
the magnetic properties of the electric current, and other improvements
in the means of communicating, superseded for some years the use of
signals made by electro-chemical decomposition.

The next important step in the progress of telegraphic invention, after
that of Mr. Soemmering, was made by Mr. Ronalds, who in 1816 succeeded
in making a perfect apparatus, that transmitted every requisite signal
with the use of only a single circuit. In the agent employed, however,
there was a retrogression to frictional electricity and the pith-ball
electrometer, for at that time the property which a voltaic current
possesses of deflecting a magnetic needle had not been discovered.

Mr. Ronalds's plan was to have, at each communicating station, a good
clock with a light paper disc fixed on to the seconds wheel, on which
were marked all the letters of the alphabet, and the ten numerals. Only
so much of this disc was exposed to view as to show a single letter
at a time, through a small aperture, as the seconds wheel revolved.
The clocks at the corresponding stations were set exactly together, so
that the same letter was exposed to view at each instrument at the same
instant. A pith-ball electrometer, connected in a single circuit with
the transmitting station, was kept distended during the transmission
of a message by charging the wire from an electrical machine; and when
the letter required to be indicated appeared at the aperture of both
instruments, the operator at the transmitting instrument instantly
discharged the electricity of the wire by touching it, and thus
caused the pith-balls to collapse. In this manner the person at the
receiving station, by attentively watching the pith-balls, and noticing
the letter that appeared at the instant of collapse, could read the
messages signalled.

Mr. Ronalds so far perfected his invention, that it worked accurately,
though slowly, through eight miles of wire insulated in glass tubes.
Having thus succeeded in putting into action his single wire
telegraph, Mr. Ronalds sought the patronage of Government for its
practical adoption, such a notion as that of establishing a telegraph
for commercial purposes not being at that time entertained. For a
length of time his application received no attention, and when at
length the Lords of the Admiralty condescended to answer, they sent Mr.
Ronalds, as the reward for his ingenuity, and as compensation for the
time and money bestowed in perfecting the invention, the expression of
their opinion--that "telegraphs are of no use in time of peace, and
that during war the semaphore answered all required purposes"! This
reply, so characteristic of the manner in which Government _employés_
generally regard anything new to which their attention is solicited,
completely disheartened Mr. Ronalds. He abandoned the Electric
Telegraph to its fate; and having gone abroad, he returned some years
later to find that, notwithstanding the _dictum_ of the Lords of the
Admiralty, telegraphs are of great use in time of peace as well as
of war, and that the old semaphore had been entirely superseded by
the means of transmission he had indicated twenty years before. Mr.
Ronalds has since received a small pension, not however as a reward
for his ingenious telegraph invention, but for his services in other
departments of science.

The discovery of the magnetic property of an electric current by
Professor Œrsted, in 1818, was most important in the subsequent
progress of telegraphic invention, though it was not applied in a
practical manner till nearly twenty years afterwards. In 1820, indeed,
M. Ampère submitted to the Academy of Sciences at Paris a telegraphic
instrument for the transmission of signals by the deflection of
needles, but he adopted the impracticable plan of the earliest
inventors, of having a separate wire for each letter of the alphabet. A
much more important contribution to telegraphic invention by M. Ampère
was the discovery of electro-magnets, which act an important part in
many recent electric telegraphs.

As the magnetic properties of a voltaic current are extensively applied
in electric telegraphs, it is desirable briefly to explain the nature
of the action of voltaic batteries before proceeding farther with the
history of the invention.

To excite a current of voltaic electricity, it is usual to employ a
series of zinc and copper plates, arranged alternately in separate
jars; or, what is now most common, in cells of gutta percha, separated
from each other in a gutta percha trough. The cells are nearly filled
with diluted sulphuric acid, and a wire is attached to each end of
the trough; one being connected with the last zinc plate, and the
other with the last copper plate of the opposite ends of the trough.
When these wires are brought into contact, electricity is instantly
generated by the action of the acid on the zinc plates. The electricity
excited by the action on the zinc in one cell is carried on to the
next, and that again excites and transfers an additional quantity to
the third cell, thus increasing in intensity to the last pair of plates
in the series. The _electric current_, as it is called, passes along
the wire, and whether the wire be one yard, or whether it be a hundred
miles long, the generation of electricity takes place the instant
that the circuit is completed, and ends the instant that the circuit
is broken. There is this difference, however, in the transmission of
electricity through a long and through a short circuit, that in the
former case the increased resistance offered by the length of the wire
greatly diminishes the quantity of electricity transmitted though it
does not perceptibly retard the velocity.

When a balanced magnetic needle is held above a short thick copper wire
whilst it is transmitting an electric current, the needle is deflected
from its natural position, and inclines either to the right or to the
left, according to the direction in which the current passes. If, for
instance, the north pole of the needle be pointed towards the copper
pole of the battery, it will be deflected towards the east, but if
the direction of the battery current be reversed, the deflection will
be towards the west. The effect instantly ceases when the current is
interrupted by breaking connection with either pole of the battery. The
copper wire, though under ordinary circumstances incapable of being
rendered magnetic, thus becomes endowed with strong magnetic properties
when it is transmitting an electric current, and acts on the magnetic
needle in the same manner as if there were an immense number of small
magnets placed along the wire across its diameter.

The magnetic property of an electric current, first discovered by
Œrsted, was applied by M. Ampère to impart magnetism to iron, by
coiling a length of copper wire round a bar of iron, taking care to
cover the wire with an insulating substance, so that when an electric
current was transmitted the electricity might not pass through the
iron. Coils of copper wire, covered with cotton or silk, can thus
impart most powerful magnetism to a piece of soft iron; but it loses
its magnetic power the instant that the electric current is interrupted.

The effect of a coil of insulated wire in increasing the magnetic
power of an electric current, was applied by M. Schweigger in 1832
to increase the sensitiveness of a suspended magnetic needle. By
surrounding a compass needle with several convolutions of covered wire,
it was found that the deflections of the needle were much greater
and more active; and he thus showed the way to the construction of
those delicate galvanometers, which indicate by their deflections
the slightest disturbance of electrical equilibrium. Schweigger may,
therefore, be considered the original inventor of the Needle Telegraph;
and as he pointed out a method of impressing symbols on paper
mechanically, by means of electro-magnets, he may be considered also as
the original inventor of Recording Electric Telegraphs.

The first near approach to the needle telegraph, now used in this
country, was made by Baron de Schilling, who, in 1832, constructed
at St. Petersburg an electric telegraph consisting of five magnetic
needles. This may be considered as the precursor of the five-needle
telegraph, first patented by Professor Wheatstone in 1837. By the
separate deflection of those needles to the right hand or to the
left, by reversing the connections with the poles of the batteries,
ten primary signals could be obtained; and by bringing two into
action at the same time, many more signals might be made than were
required for indicating the letters of the alphabet, and they could
be appropriated to express several words. For the action of this very
efficient telegraph only five wires were required, and the signals
being all primary ones, the messages might have been transmitted very
quickly.[6] In a subsequent modification of the telegraph, he contrived
to make all the signals with one magnetic needle alone, by repeating
the deflections to the right and to the left, as done in the needle
telegraph now generally used in England.

Another step made by Baron de Schilling was the invention of an
alarum to call attention when a message was about to be sent. Some
contrivance of this kind was considered essential in the early days of
the practical application of the Electric Telegraph, as no one then
contemplated that telegraphic communications would be so frequent as
to require a person to be always near the instrument, waiting for the
receipt of messages.

Baron de Schilling's alarum was very simple. One of the magnetic
needles acted as a detent which held a weight suspended, and when
the needle was deflected, the weight fell upon a bell. The alarums
subsequently invented were constructed on the same principle, but
instead of employing one of the magnetic needles as a detent, an
electro-magnet was used for the purpose, and clock mechanism was
introduced to sound a bell continuously, as soon as it was set in
action by the withdrawal of the detent. At the present time alarums are
not used in the regular stations of the electric telegraph companies;
the sound of the needles, as they strike against the ivory rests on
each side, being sufficient to call the attention of the clerks, who
are in constant attendance.

We have hitherto been enabled to trace, step by step, the advances
made at intervals--years asunder--in bringing the Electric Telegraph
into practical use; but we are now approaching a time when it becomes
difficult to enumerate, and impossible to describe within reasonable
compass, the numerous inventions that were patented and otherwise made
known for giving greater efficiency to that means of communication.

In the early part of the year 1837, the electric telegraphs of Mr.
Alexander, of Edinburgh, and of Mr. Davy, were publicly exhibited
in London, and excited much attention; though, at that time it was
not supposed that it would be possible to make use of that means of
communication for general purposes. Mr. Alexander's telegraph was the
same in principle as those of M. Ampère and of Baron de Schilling,
though in some respects not so efficient as either, for its action was
slow, and it required a separate wire for each letter of the alphabet.
It was considered a great advantage of this telegraph at the time,
that it exhibited actual letters of the alphabet, instead of symbols.
This was effected by having the twenty-six letters painted on a board,
and concealed from view by a number of small paper screens, which were
attached to magnetic needles. When any of the needles was deflected
by sending an electric current through the surrounding coil, the
screen was withdrawn and exposed the letter behind. Twenty-six keys,
resembling those of a pianoforte, were ranged in connection, one with
each wire, and on pressing down any one of the keys, contact was made
between the battery and the wire connected with its associated magnetic
needle; and in this manner, messages might easily be transmitted
and read. The objections to this telegraph, in the form in which it
was exhibited, were not only the impracticability of laying down
and insulating so many wires, but the paper screens attached to the
needles impeded their action, and rendered the transmission a very slow
process. It is questionable, indeed, whether that telegraph could have
been worked at all through a circuit of many miles.

Mr. Davy's telegraph was similar to that of Mr. Alexander's, though
much more compact and better arranged. The letters were painted on
ground glass, lighted behind, so that when the screens were withdrawn
the letters were seen in transparency.

[Illustration]

Professor Wheatstone, who had for some previous years been endeavouring
to perfect a practical electric telegraph, took out his first patent
in 1837. It closely resembled in general features the telegraph of
Baron de Schilling. It consisted of five magnetic needles, ranged side
by side on a horizontal line that formed the diameter of a rhomb. The
needles were suspended perpendicularly, being kept in that position by
having the lower ends made slightly heavier than the upper. The rhomb
was divided into thirty-six equal parts by ten cross lines, and the
needles were placed at the points where the lines intersected, as shown
in the diagram.

At each intersection, and along the boundary lines of the rhomb,
letters were marked, any one of which might be pointed at by the
combined action of two of the needles. Thus, if the two extreme needles
were deflected inwards, one towards the left and the other towards the
right, they would point to the letter _A_ at the top of the rhomb.
If the extreme needle on the left and the fourth one were similarly
deflected, they would point to the letter _B_; and thus all the letters
marked on the intersections of the lines could be pointed to. A
telegraph that could be worked with five circuits came within the range
of practicability, and it was put into operation on the Great Western
Railway as far as Slough, a distance of 18 miles.

When the work of actually making communication by insulated wires
between places far apart came to be done, much difficulty arose as to
the best and cheapest mode of doing it. The plan first attempted was
to surround the wires with pitch, and to bury them in a trench in the
ground. But this was found to be attended with great inconvenience, for
the pitch cracked, and electric communication was established between
the adjacent wires. The method of suspending the wires on posts was, we
understand, suggested by Mr. Brunel, who had seen wires so suspended
for other purposes on the Continent, and he recommended it to Mr. Cooke
for the Electric Telegraph. The plan was tried with success, and
was generally adopted by the Electric Telegraph Company in extending
their lines over the country. We shall have occasion to revert to this
practical part of the subject, when describing more particularly the
means of making communication from one place to another.

In continuing the history of the invention, as regards the different
modes by which communications are transmitted along the insulated
wires, the next telegraphs that deserve notice are those of Dr.
Steinheil, which became known also in 1837. One of his telegraphs made
the signals by sounds, produced by magnetic needles striking, when
deflected, against bells of different tones. By another telegraph
of his invention the symbols where marked upon paper by small tubes
holding ink, fixed to the needles. In this manner the letters of the
alphabet were indicated by dots upon a strip of paper, kept slowly
moving by clock mechanism. This telegraph could be worked by a
single circuit; and it appears that Dr. Steinheil was the first who
discovered, or at least who practically applied, the conducting power
of the earth for the return current. Each circuit, therefore, consisted
of only a single wire; the wire that had been previously used to
complete the circuit being superseded by burying in the earth, at each
terminus, a small copper plate. Dr. Steinheil also introduced the use
of galvanized iron wire. An electric telegraph of this construction was
put into operation at Munich, through a distance of 12 miles.

[Illustration]

In the following year Messrs. Cooke and Wheatstone so far simplified
the arrangements of their needle telegraph as to make all the requisite
signals with two needles. With a single combined battery and two wires
six primary signals are thus obtained; and by repeating the deflections
and combining the action of the two needles, all the letters can
be readily and quickly indicated. A single needle instrument was
invented by Messrs. Cooke and Wheatstone, but as there are only two
primary signals, one to the right and one to the left, the deflections
are necessarily repeated more frequently, and the transmission is
consequently more slow. The accompanying diagram represents the
alphabet of the single needle instrument. The deflections for each
letter commence in the direction of the short marks, and end with
the long ones. Thus, to indicate the letter _R_, the needle is first
deflected once to the left and then once to the right; and the letter
_D_ has the deflections reversed, beginning with one to the right and
ending with one to the left. In no instance does it require more than
four deflections to indicate a single letter, yet the transmission
with the double needle is found so much quicker that the single needle
instrument is only rarely used.

At the end of each word, it is customary for the clerk at the receiving
station to indicate, by a deflection of the needle to the right, that
he understands, or by a deflection to the left, that he does not
understand, and in the latter case the word is repeated. In the early
days of the Electric Telegraph, the transmission of 40 letters a minute
with the double needle instrument was considered quick work; but the
practised clerks will now transmit one hundred letters in that time,
which is as fast as any person can write with pen and ink.

Since the invention of the double and single needle telegraphs there
have been many modifications in the instruments, to make them work
more promptly and with less vibration; but in all essential parts
the telegraphs of Messrs. Cooke and Wheatstone remain unaltered, and
continue to be generally used in this country.

Of the numerous other telegraph instruments that have been invented
since 1837, that of Mr. Morse is in most general use, especially on the
Continent and in America. Mr. Morse, indeed, claims to be the first
inventor of a practical Electric Telegraph; for, according to his
statement, he, in 1832, invented a telegraph, which was in principle
the same as the one now in use. It was not, however, till September,
1838, that he made his instrument known in Europe, by sending a
description of it with a model to the Academy of Sciences at Paris.
Mr. Jackson, an American, disputed with Mr. Morse for the honour of
the invention, and when the latter asserted that he had described his
telegraph in 1832, to some passengers on board a packet-boat, Mr.
Jackson affirmed that it was he who described it on that occasion, and
that Mr. Morse, being present, got the idea from him. It is painful
and difficult to decide when we find two claimants thus directly
in opposition to each other, and mutually preferring charges of
falsehood and fraud. The only safe guide in such cases is to refer to
the earliest published and authentic descriptions of the inventions;
and, following that guidance, the invention of what is called Morse's
telegraph must be attributed to him whose name it bears; but we must,
according to the same rule, date it several years later than 1832.

Mr. Morse's telegraph is a recording instrument, that embosses
the symbols upon paper, with a point pressed down upon it by an
electro-magnet. The symbols that form the alphabet consist of
combinations of short and long strokes, which by their repetitions and
variations, are made to stand for different letters. Thus a stroke
followed by a dot signifies the letter _A_; a stroke preceded by a
dot, the letter _B_; a single dot, the letter _E_; and in this manner
the whole alphabet is indicated, the number of repetitions in no case
exceeding four for each letter. The letters and words are distinguished
from one another by a longer space being left between them than
between each mark that forms only a part of a letter or of a word. The
annexed diagram represents the symbols for the whole alphabet.

[Illustration]

The mechanism of this telegraph instrument is very simple. The
transmitter is merely a spring key, like that of a musical instrument,
which, on being pressed down, makes contact with the voltaic battery,
and sends an electric current to the receiving station. The operator at
the transmitting station, by thus making contact, brings into action an
electro-magnet at the station he communicates with, and that pulls down
a point fixed to the soft iron lever upon a strip of paper that is kept
moving by clockwork slowly under it. The duration of the pressure on
the key, whether instantaneous or prolonged for a moment, occasions the
difference in the lengths of the lines indented on the paper. A single
circuit is sufficient for this telegraph, and a boy who is practised
in the use of the instrument will transmit nearly as many words in a
minute as can be sent by the double needle telegraph with two wires.

The working of Mr. Morse's telegraph, it will be observed, depends
altogether upon bringing into action at the receiving station an
electro-magnet of sufficient force to mechanically indent paper. Now
the resistance to the passage of electricity along the wires diminishes
the quantity transmitted so greatly, that at long distances it would
be almost impossible to obtain sufficient power for the purpose,
if it acted directly. To overcome that difficulty, an auxiliary
electro-magnet is employed. The electro-magnet which is directly in
connection with the telegraph wire is a small one, surrounded by about
500 yards of very fine wire, for the purpose of multiplying as much as
possible the effect of the feeble current that is transmitted. The soft
iron keeper, which is attracted by that magnet, is also very light,
so that it may be the more readily attracted. This highly sensitive
instrument serves to make and break contact with a local battery, which
brings into action a large electro-magnet, and as the local battery and
the magnet are close to the place where the work is to be done, any
required force may be easily obtained. By this means the marks may be
impressed on the paper at distances of 400 miles or more apart.

This is a very efficient and remarkably simple telegraph, and as it
operates with a single wire, it has completely supplanted the needle
telegraph on the Continent; though the liability to error, common to
all manipulated telegraphs, is considerably increased by this mode of
transmission, nor can unintelligible signals be indicated and corrected
so readily as by the needle instrument.

There have been several modifications of Mr. Morse's telegraph, for the
purpose of increasing the rapidity of its action and the distinctness
of the marks. The most important of these was made by Mr. Bain, who
in 1847 applied for this purpose the method of impressing the symbols
on paper by electro-chemical decomposition. Mr. Davy had, in 1843,
taken out a patent for the application of electro-chemical marks to
telegraphic purposes, but his method was not sufficiently practical
to be brought into use. Mr. Bain adopted an alphabet of short and
long strokes, similar to that of Mr. Morse; but instead of making and
breaking contact by a key pressed down by the finger, he punched holes
in a strip of paper, corresponding in lengths and positions to the
marks intended to be transmitted. A small metal spring, connected with
the voltaic battery, pressed upon a metal cylinder attached to the
telegraph wire, and when the spring and cylinder touched, an electric
current was transmitted. The strip of punched paper was placed upon the
cylinder so as to interrupt the circuit, excepting in the parts where
the apertures allowed the spring to make contact; therefore when the
strip of paper was moved along, an electric current was transmitted
through the apertures, and it was stopped when the paper intervened.
At the receiving station, paper well moistened with a solution of
prussiate of potass and nitric acid was placed upon a corresponding
cylinder to receive the message, and a piece of steel wire was kept
steadily pressed upon it as it moved along. The action of the electric
current at the parts where it was transmitted caused the acid to enter
into combination with the steel, and the consequent deposition of iron
on the paper was instantly converted by the prussiate of potass into
Prussian blue. On the parts where the electric current was interrupted
no action took place, and thus numbers of short and long marks were
made on the paper, corresponding to the lengths of the apertures
on the prepared message. A representation of the punched paper for
transmitting the word "Bain" is shown in this diagram.

[Illustration]

As electro-chemical action takes effect much more rapidly than the
mechanical movement of an indenting point, Mr. Bain's telegraph could
work much faster than Mr. Morse's. We have been informed that as many
as 1,000 letters per minute have occasionally been transmitted by
this means from Manchester to London. The disadvantage attending that
mode of transmission arises from the tedious process of punching the
message preparatory to transmission; and though circumstances may arise
in which it would be of great importance to adopt this rapid system
of transmission with a single wire, it has been yet but little used
in this country by the Electric Telegraph Company, who purchased Mr.
Bain's patent for £10,000.

Another modification of Mr. Morse's telegraph, which has been more
extensively adopted in England, consists in merely substituting marks
made on paper by electro-chemical decomposition for those indented
by pressure. It has been found desirable in practice, however, to
introduce an auxiliary electro-magnet, called a "picker," for making
and breaking contact, by which arrangement the dotted marks can be
made by a local battery, and any required amount of electric power be
obtained. The marks produced in this manner are more distinct, and
are more quickly made, than by mechanical pressure. By a more recent
application of Mr. Morse's system, the marks are made on paper with ink
flowing through a glass pen, in the same manner as in the telegraph of
M. Schweigger, already noticed. As the strip of paper is moved along,
a continuous line is thus drawn on the paper. When no signals are
being transmitted the line is straight, but when an electric current
is sent through the wire, it brings into action an electro-magnet,
which attracts the penholder on one side, and alters the direction of
the mark. The transmission is effected by making and breaking contact
with a key, and the continuance of the divergence of the mark from
its normal direction is regulated by the duration of pressure on the
key. The symbols are thus made by deviations from the straight line,
of different lengths and of varied combinations. Practical application
alone can determine whether this mode of making the marks possesses any
advantage over Mr. Morse's original plan. The patent for this telegraph
was granted to Mr. Wilkins in 1854, but a similar instrument, applied
to the notation of astronomical observations, was shown in the American
department of the Great Exhibition of 1851.

The recording telegraph instruments hitherto noticed impress on the
paper only hieroglyphical symbols, which require long practice to
decipher readily. It has, from the first practical application of the
invention, been considered highly desirable that the letters of the
alphabet should be indicated and printed in their proper forms, so that
the momentary transmission of an electric current should leave behind
a durable impression that could be read without difficulty. Professor
Wheatstone and Mr. Bain separately attempted to accomplish this desired
object by the invention of Printing Telegraphs, which print messages
from types. It is a question in dispute which of them was the first
to design a telegraph of this kind. In 1845, Mr. Bain had a printing
telegraph in operation experimentally on the South-Western Railway,
for a distance of seven miles, and we are not aware that Professor
Wheatstone ever succeeded in working his printing instruments when
separated at a distance from each other. In principle, both inventions
were similar. A wheel, into the periphery of which were inserted types
of the twenty-six letters, was made to rotate in close proximity to a
piece of paper, over which was placed a blackened surface that would
leave a mark on the paper when pressed upon. When the required letter
came opposite the paper, the type-wheel was stopped and forced against
it, so that the letter was impressed, and the black from the interposed
surface marked the form of the type. The paper was then moved forward
to leave space for the next letter, and thus a continuous message could
be printed. The objection to these instruments was the uncertainty of
stopping the type-wheel at the proper point, so as to avoid printing
wrong letters; and when the instruments became thus irregular, they
continued so till they were again adjusted. This difficulty has since
been overcome; and by the combined efforts of Mr. House in America,
and of Messrs. Brett in this country, the printing telegraph has
attained a high degree of perfection. The mechanical arrangements of
the instrument, though very complex, consist essentially, like those of
Mr. Bain and Professor Wheatstone, in having a type-wheel, which, by
the action of the operator at the transmitting instrument in making and
breaking contact, moves or stops at the required point, and the letters
are printed by forcing the paper against the type by an electro-magnet.
The movements of the type-wheel are regulated by an electro-magnet, and
one great improvement introduced by Mr. Brett prevents the continuance
of error, should any be made during transmission, by bringing the
type-wheel to its first position after printing each letter, so that
if a wrong letter be printed, the subsequent letters will not continue
erroneous. This printing telegraph works with a single wire, but its
operation is rather slow.

The last recording telegraph we shall notice is the one invented by the
author, which transmits copies of the handwriting of correspondents.
The communication to be transmitted is written upon tin foil, thinly
coated with varnish, with a pen dipped in an ink composed of caustic
soda and colouring matter. The alkali detaches the varnish, and when
the surface is washed over with a wet sponge, the metal is exposed
on those parts written upon, the writing appearing metallic on a
dark ground. The message is then placed round a metal cylinder that
is connected with the line wire from the receiving station. A brass
point, in connection with the voltaic battery, lightly presses on
the message as the cylinder rotates, so that the electric circuit is
made and broken through the message as it passes under the connecting
point, the coating of varnish on the foil being sufficient to interrupt
the electric current in those parts where the point is resting upon
it. On a corresponding cylinder in the electric circuit, at the
receiving station, paper moistened with a solution of prussiate of
potass and nitrate of soda is placed to receive the message; and it
is pressed upon by the point of a steel wire, in connection with the
communicating wire. The accompanying diagram will assist in explaining
the arrangement.

The cylinder of the instrument is shown at _a_; _b_ is the metal
style connected by the wire _g_ with one of the poles of the voltaic
battery; _o_ is the arm which holds the style and serves to insulate
it from the rest of the apparatus; _c_ is a fine screw on which that
arm traverses as the cylinder revolves; _d d_ are cog-wheels to turn
the screw. The speed of the instrument is regulated by the fan _e_; _f_
is the impelling weight, and _h_ the wire connected with the distant
instrument. The receiving and the transmitting instruments are alike,
the only difference between them being that the style of the copying
instrument is steel instead of brass wire.

[Illustration]

As the cylinder _a_ is connected by the wire _h_ with the distant
instrument, and through it with one of the poles of the voltaic
battery, the electric circuit is completed by passing from _g_
through the tin foil message, or through the paper placed on the
cylinder. This will be the case whenever the style of the transmitting
instrument is pressing on the metallic writing; and at those times the
electro-chemical action of the voltaic current will produce a blue mark
on the paper of the receiving instrument, by the deposition of iron and
its combination with the prussiate of potass. The circuit will in like
manner be interrupted whenever the point _b_ presses on those parts
of the message where the varnish is not removed; and thus, as the two
cylinders revolve, there will be a succession of small blue marks on
the parts where the writing allows the electric current to pass. As the
arms that carry the points traverse on screws, they are drawn along
as the cylinders rotate, so as to press on fresh parts of the message
and of the paper at each revolution. The steel point would therefore
draw a series of spiral lines on the paper, if the electric current
were not interrupted; but the interposition of the varnish breaks those
lines, and as the point passes over different portions of the letters
at each revolution of the cylinder, the marks and the interruptions on
the paper correspond exactly with the forms of the letters, and thus
produce a copy of the writing placed upon the receiving cylinder, in
blue characters on a yellowish ground. Or the message may be written
on unprepared tin foil with a pen dipped in varnish; in which case the
writing will be copied in white characters on a ground of dark lines,
as in the accompanying specimen, _A_ being the writing on tin foil, and
_B_ the message received.

It is essential to the perfect working of the copying telegraph that
the corresponding instruments should rotate exactly together. This is
effected by an electromagnetic regulator, which being put in action by
one instrument, governs the movements of the distant instrument with
the greatest exactness, as proved at a distance of 300 miles.

It might be supposed, as the points must traverse several times over
the same line of writing to copy it, that the process is a slow one;
but in consequence of the rapidity with which the cylinders revolve,
this is not the case. The ordinary speed is one rotation in two
seconds, and at that rate three lines of writing, containing sixty
words, would be copied in one minute, which is three times as fast as
an expeditious penman can write.

[Illustration]

The advantages proposed to be gained by the copying telegraph,
in addition to its increased rapidity of transmission, are the
authentication of telegraphic correspondence by the signatures of the
writers, freedom from the errors of transmission, and the maintenance
of secrecy. As a special means of obtaining secrecy, the messages may
be received on paper moistened with a solution of nitrate of soda
alone, in which case they would be invisible until brushed over with a
solution of prussiate of potass, to be applied by the person to whom
the communication is addressed.

Professor Wheatstone has recently contrived an improvement in his index
telegraph, which was described by Professor Faraday in a lecture at
the Royal Institution in June last. Its chief merit, however, consists
in the beauty of the mechanism, for it is essentially the same as the
index telegraphs he and others have previously invented, with the
substitution of magneto-electricity for the moving force.

Having now traced the history of the invention of the instruments by
means of which messages may be transmitted, it becomes necessary to
describe the methods employed for making the electrical connection from
one place to another. This part of the electric telegraph system is,
after all, the most essential to its efficient working, and bears the
same relation to the transmitting instruments that the structure of a
railroad does to locomotive engines in the system of railway conveyance.

The fact that an electric current might be sent through a long circuit
had been established by Dr. Watson, in conjunction with other Fellows
of the Royal Society, in 1747, when they sent the charge of a Leyden
jar through two miles of wire, supported upon short sticks driven into
the ground; the wire at each terminus being connected with the earth
for the return current. This method of insulation and conduction fully
answered the purpose, and served to determine the great velocity with
which electricity is transmitted, for no perceptible interval occurred
between the discharge of the Leyden jar at one end of the circuit, and
its effect at the other extremity.

Mr. Ronalds made the next experiment on an extensive scale, by
insulating eight miles of wire in glass tubes, the wire being carried
backwards and forwards for that distance on his lawn at Hammersmith.
That mode of insulation was found very efficient. It was, indeed, too
perfect, for the difficulty arose of discharging the electricity from
the wire after the charge had passed through it.

The length of telegraphic communication established at Munich, in 1837,
by Dr. Steinheil, was an important practical advance in the system of
extending and insulating the wires, and deserves consideration, not
only from the extent to which it was carried into practical operation,
but from the circumstance that the earth was employed to form the
return circuit. The wires appear to have been carried through the city
by extending them from the church towers and other elevated buildings.
That plan, indeed, presents so many facilities for passing telegraph
wires through towns, that it is not improbable it may be ultimately
adopted in this country.

Though the conducting power of the earth was thus early made use of for
one-half of the circuit, the fact seems to have been unknown in England
at the time of laying down the telegraph wires to Slough in 1845,
for a separate wire was then used for the return current. Some years
afterwards, indeed, Mr. Bain laid claim to the discovery; but the fact
that the conducting power of the earth had been previously applied to
the purpose by Dr. Steinheil has been incontestably proved.

In the early stages of the practical application of electric telegraphs
in this country, Mr. Cook took an active part in overcoming the
numerous difficulties attending the proper protection and insulation
of the wires. In the first instance, the plan of burying the wires in
trenches was tried, but with very indifferent success, as the asphaltum
and other resinous substances with which it was attempted to insulate
them were inadequate for the purpose, and allowed the electricity to
escape from wire to wire. The method of supporting the wires on tall
posts was then adopted by Mr. Cooke, the wires being insulated from
the posts at the points of suspension, by passing them through quills.
Various improvements have since been made in the insulators, and the
plan most in favour at present is to pass the wires through globular
earthenware or glass insulators, attached to the posts, as shown in the
annexed diagram. The wires themselves are about one-sixth of an inch in
diameter; they are made of iron coated with zinc, or galvanized, as it
is termed, to protect them from rust.

[Illustration]

Notwithstanding the great care taken to insulate the wires at the
posts, a large quantity of the electricity escapes in wet weather,
and returns to the battery without having reached the most distant
stations, and thus not unfrequently the communications are interrupted.
The author is of opinion that the loss of electricity in wet weather
is occasioned rather by communication from one wire to another
through the moist atmosphere, than by defective insulation at the
posts. In confirmation of this opinion it may be stated, that he has
experimentally determined that a working electric current might be
transmitted from London to Liverpool, if all the points of attachment
were connected by water with the surface of the ground, provided that
the rest of the wire were insulated.[7]

The use of gutta percha as an insulating covering for wire has given
rise to a new era in telegraphic communication. Gutta percha is an
excellent insulator, and wire covered with two coatings of that
material, about one-sixteenth of an inch each, is so far protected,
that 100 miles of it immersed in water transmits an electric current
from a powerful voltaic battery with very trifling loss. This
perfection in insulation has greatly facilitated the establishment of
telegraphic communication between England and the Continent. The first
attempt to establish a submarine circuit between Dover and Calais took
place on the 28th of August, 1850. A single copper wire, about the
thickness of a common bell wire, coated thickly with gutta percha, was
laid across the English Channel experimentally, without any protection.
It proved sufficient for the transmission of an electric current, and
several messages were sent through it between Dover and Calais; but
it was far too feeble to resist the action of the waves, and the
following day it was cut through by friction against the rocks, and the
communication was stopped.

[Illustration]

The plan afterwards adopted for a permanent submarine line was to
enclose five similar wires in a hollow iron wire cable. The wires
were first slightly twisted, to prevent them from being broken when
stretched. They were then covered with hempen yarn, to protect the
gutta percha from attrition, and they were thus introduced into the
hollow cable, of which they formed the core. The accompanying woodcut
represents this structure of the cable; the five twisted wires are
shown at _C_; _B_ represents the same covered with hemp yarn; and
_A_ a portion of the completed cable, constructed of thick iron wire
galvanized. This cable has now been laid down for seven years, and with
perfect success. Its strength has often been severely tested, as it has
been sometime drawn up by ships' anchors, and considerably strained;
but it has not been broken, and the insulation is almost perfect. The
success of this submarine cable has induced the extension of that means
of communicating with the Continent, and similar submarine telegraph
cables have been laid down from Dover to Ostend, from Harwich to the
Hague, from Scotland to Ireland, and across the Mediterranean Sea as
far as Malta. The weight and the cost of those cables present a serious
obstacle to their adoption in forming a telegraphic communication with
America; and when it was determined to attempt to establish electrical
connection with the New World, a different form of cable was adopted.
The conductor of the electric current in the Atlantic cable is composed
of seven strands of fine copper wire twisted together, the aggregate
thickness of which is not greater than the single copper wire of other
submarine cables. This fine copper cord is covered carefully with gutta
percha; it is then coated with tarred hemp, and is protected externally
by an iron wire rope, composed of numerous strands of fine wire. The
form and exact size of the cable are shown in the accompanying drawing
and section. The central dots in the section are the conducting wires
round which are the gutta percha and hemp, and the outer rim represents
the iron wire casing.

[Illustration]

[Illustration]

The successful laying down of so frail a cable, after many failures,
affords good ground for hoping that, with the experience already
gained, subsequent efforts will prove more satisfactory and much
less expensive than this first attempt to establish telegraphic
communication with America. The most questionable part of the problem
has, indeed, been already solved; for the transmission of electric
signals, through that length of submerged wire, was at one time
doubted; and though the communication through the present cable has
ceased, it has sufficiently established the fact, that telegraphic
communication with America is a practicable undertaking.

The excellent insulation obtained by means of gutta percha covered
wires has caused a return to the original plan of burying the wires in
trenches in the ground. The British and Submarine Telegraph Company
make all their communications by that means; the number of coated wires
required being enclosed in iron tubes, and laid in the ground along
the common roads. That plan is, however, attended with considerable
disadvantages. In the first place, the cost of the coated copper wire
is more than quadruple that of galvanized iron wire; and though copper,
compared with iron, offers only one-seventh part the resistance to the
transmission of electricity, yet the thin wire employed is scarcely
equal in conducting power to the galvanized iron wire usually supported
on posts. The quantity of electricity transmitted is therefore less,
and the comparative intensity of it is greater.

Another difficulty attending the use of insulated wires buried in the
ground arises from a very peculiar condition of electrical conduction,
that could scarcely have been anticipated. The wire, coated with
gutta percha, and surrounded externally with water or with moist
earth, becomes an elongated Leyden jar; the gutta percha representing
the glass, the wire the inside coating, and the water the conducting
surface outside. Thus, when electricity is transmitted through such a
medium, a portion of the charge is retained after connection with the
battery has been broken. This effect increases with the length of the
wire and the intensity of the current; and it materially interferes
with the working of many telegraph instruments. In some experiments
with the copying telegraph at the Gutta Percha Works in the City Road,
it was found that through a circuit of 50 miles of wire immersed in
water, the mark made by electro-chemical decomposition on paper had
a tendency to become continuous; so that instead of ceasing to mark,
when the varnish interrupted the current, a line was drawn continuously
on the paper, though the stronger marks where the current passed were
sufficient to make the writing legible. The retention of the charge
was also shown still more remarkably by the explosion of gunpowder by
the electricity retained in the wire half a minute after connection
with the battery had been broken. It is owing to the retention of the
electricity by the wire that the slowness with which the messages
through the Atlantic cable were transmitted is to be attributed, and
not to the length of the cable. The rate of one word a minute was the
average speed of transmission when the first messages were sent through
the wire. The effect of the _retardation_ of the electric current is
comparatively insignificant and were it not for the peculiar action of
the surrounding water, the messages might have been transmitted twelve
times faster than they were.

The cost of constructing a telegraphic line has greatly diminished
with the increased facilities of insulating the wires, and since the
expiration of patents, which conferred a monopoly on certain plans of
doing so. The cost to the Great Western Railway Company for a line of
six wires to Slough, was £150 per mile, with comparatively low and
slender posts and very imperfect insulation. The cost of the same
number of wires at the present day would not be one-half that sum, with
thicker wires and better insulation.

It is customary in England to restrict the suspension of telegraphic
wires to railways, from the notion that the protection of railways is
necessary to prevent wilful damage to the wires; and as the Electric
Telegraph Company have made exclusive arrangements with all the railway
companies out of London, the competing telegraph companies have
preferred to lay their wires underground rather than incur the supposed
risk of damage to the wires if suspended from posts on common roads,
though by this means the cost of construction is at least quadrupled.
The protection which railways afford is, however, more imaginary than
real, for any one inclined to interrupt the communication could easily
do so; and if on common roads proper precautions were taken in fixing
the posts, and a heavy penalty were imposed on wilful offenders, the
common roads and open fields would, there can be little doubt, offer
as safe a course for the telegraphic wires as railways.

The conducting power of the earth is now employed by all electric
telegraph companies for one-half of every circuit. Thus, whether a
communication be sent from London to Liverpool, to Edinburgh, Paris,
or Brussels, the moist earth serves to complete one-half of the
communication. In the telegraphic circuit between London and Liverpool,
for example, the insulated wire is connected at each end with the
earth by being soldered to a copper plate, which is buried a few feet
underground, so as to insure its being always surrounded with moisture.
To improve the connection of this plate with the earth, it is customary
to bury with it a quantity of sulphate of copper, the solution of which
surrounds the earth-plate with a better conducting liquid than water,
and thus extends the connecting surface. The gas pipes or water pipes
are sometimes employed for the attachment of the wires instead of an
earth-plate, but the latter is generally preferred.

In arranging a telegraphic circuit, the voltaic batteries and the
instruments are introduced at breaks in the telegraph wire. The course
of the electric current is from the copper end of the battery through
the transmitting instrument, then along the wire to the receiving
instrument; from that it passes to the earth and is thus returned to
the transmitting station, where it completes the circuit by being
conducted from the earth-plate to the zinc end of the voltaic battery.
The arrangement for completing the circuit will be more clearly
understood by reference to the accompanying diagram.

[Illustration]

The wire from _C_, which is the copper pole of the voltaic battery,
is connected with the instrument _A_; the electric current is then
transmitted along the wire _D_ to the receiving instrument _B_; thence
it is transferred to the earth-plate _E_, passes through the earth to
the corresponding plate _E´_, which is connected with _Z_, the zinc
pole of the battery. When a communication is returned from _B_ to _A_,
a similar arrangement is made; the wires connected with the instruments
being so arranged as to bring into action a voltaic battery at _B_, and
to throw out of circuit the one at _A_; for the connection with the
battery is only made when the transmitting instrument is worked.

Since all the electric telegraphs in different parts of the world are
connected with the earth, as one portion of the circuit, it might
be supposed that the various currents would mingle, and occasion a
confusion of messages; but it must be borne in mind that no electric
current is formed until a communication be made from one pole of a
voltaic battery to the other, and as such communication can only be
completed through the insulated wire, the earth-currents cannot
mingle, but each one passes to the proper terminus of its respective
battery. The accompanying diagram and explanation may serve to remove
the difficulty of understanding why the two circuits are maintained
quite distinct.

[Illustration]

The letters _A_ _B_ represent the wires making communications between
the batteries _D_ and _E_, and the telegraph instruments _I_ _O_ at the
receiving station. The electricity from the copper end of the battery
_D_ would be conducted along _A_ through the instrument _I_, and by
the wire _K_ to the earth-plate _H_. It would be then transmitted
through the earth on its return to the battery, in the direction of the
arrows, to the other earth-plate _G_, and thence it would find its way
to the zinc pole of the battery _D_, and complete the circuit. In the
same manner, the electric current from the copper end of the battery
_E_ would be transmitted through the wire _B_, and would complete its
current also by means of the earth-plates _G_ _H_, and would traverse
the course indicated by the arrows, and return to the zinc end of
_E_. Though both electric currents traverse the same wire from the
instruments _I_ _O_ to the earth-plate _H_, and are thence transmitted
through the earth to a single plate, _G_, at the transmitting station,
there is no mingling of currents, the electric current of each battery
being kept as distinct as if separate wires were used both for the
transmitted and the return current. It would, indeed, be as impossible
for the separate currents transmitted from the two batteries to be
mingled together, as it would be for the written contents of two
letters enclosed in the same mail-bag to intermix.[8]

The length of telegraph lines at present laid down by the several
telegraph companies in Great Britain, exceeds 10,000 miles. To complete
those lines required 40,000 miles of wire, and there are 3,000 persons
engaged in the transmission of telegraphic intelligence.

In North America there is a direct communication from New York to New
Orleans, a distance of 2,000 miles, through the whole length of which
wires messages can be transmitted without any break. Wires have also
been suspended on lofty posts across the Indian Peninsula, where no
railways have been yet laid down. Lines of insulated wire, partly
submerged in the sea, partly buried underground, and partly suspended
on posts in the air, place London and Vienna in direct communication;
and other telegraph lines are in the course of construction, which will
unite London with Africa: and a complete net-work of telegraph wires is
spreading over the face of Europe.

It will not be long before this system of communication is connected
with a similar one in America. The failure of the cable already laid
down has confirmed the opinion of the author, expressed in papers
read at meetings of the British Association for the Advancement of
Science, and in his work on Electricity, that the conducting wire
should be sufficiently strong to be self-protective, without requiring
an external coating of iron wire rope. A conducting copper wire, a
quarter of an inch in diameter, covered with gutta percha and tarred
hemp, would be more flexible and stronger than the combined cable;
and it being a much better conductor of electricity, the rapidity of
transmission would be greatly increased.

The effect of the establishment of competing telegraph companies in
England has been to diminish the charge for transmitting messages, in
some instances to one-fifth of the rate formerly demanded; and when
further experience in the construction of telegraphic lines, and the
adoption of more rapidly transmitting instruments, have facilitated
and improved the means of communication, we may anticipate that
correspondence by Electric Telegraph will in a great measure supersede
the transmission of letters by post.




ELECTRO-MAGNETIC CLOCKS.


The invention of Electro-Magnetic Clocks closely followed the
introduction of the electric telegraph; and Professor Wheatstone,
to whom the world is principally indebted, in conjunction with Mr.
Cooke, for the perfection and application of the needle telegraphic
instrument, claims also to be the original inventor of Electro-Magnetic
Clocks. His claim is, however, disputed by Mr. Bain, who asserts that
he was the first who conceived the idea of applying the power of
electro-magnets to the regulation and movements of clocks, and it must
be admitted that he brought the invention into a working state.

In the first stage of the invention, the object attempted to be
attained was to regulate several clocks, once an hour--or oftener, if
required--so that they might all indicate precisely the same time.
For this purpose Mr. Bain took for a standard time-keeper a clock of
the best possible construction, placed in circumstances favourable
to maintaining accuracy. The minute-hand of his clock, the instant
that it pointed to the hour, made connection with a voltaic battery
that brought into action a series of electro-magnets attached to the
clocks to be regulated; one of them being fixed on the top of each
clock. Its momentary action was made to collapse a pair of clippers,
which in closing seized the minute-hand of the clock to which it was
attached, and brought it to the hour point. Thus all the clocks in
the series could be regulated every hour, for the collapse of the
clippers pushed the hand forward if it were too late, or thrust it
back if it had gained. Mr. Bain contemplated the application of this
contrivance to all the public clocks of a town, by having wires laid
down in the streets to connect them in one voltaic circuit. Such a
plan would, however, have involved greater expense and trouble in its
accomplishment than the object seemed to merit; but the regulation
of any number of clocks in a large establishment might have been
practicable by that means. We are not aware, however, that this mode
of regulating clocks by electricity was ever adopted, and it has since
been superseded by an arrangement made by Mr. Shepherd, junior, to be
presently noticed.

Improving on this first application of electro-magnetism to the
regulation of clocks, Mr. Bain afterwards employed the power to keep
the clocks in action, so that each clock might be propelled by magnets
alone, without any weight, and without the ordinary train of wheels.

Every one acquainted with the mechanism of a clock is aware that the
weight communicates motion to a train of wheels, and that the movement
is regulated by the vibration of a pendulum, which is acted on by
the last wheel of the train. That wheel, called the escapement, is
so formed, that each tooth catches in succession into a detent fixed
on the pendulum near the point of suspension, which allows one tooth
to pass at each double vibration. The pendulum, therefore, governs
the movement of the train of wheels by checking the escapement, and
allowing the teeth to pass one by one; and as pendulums of given
lengths vibrate in given times, if their actions be not interfered
with, the clocks will keep regular time. But the pressure of the
escape-wheel against the detent, and the consequent friction, prevent
the pendulum from acting freely. In the best made clocks there are
special contrivances to detach the pendulum as much as possible from
the wheels, and likewise to compensate for variations in the length of
the pendulum by change of temperature.

In the clocks actuated by electro-magnetism, the movement of the
pendulum is not maintained by repeated impulses of the escape-wheel, as
in ordinary clocks, but by magnetic attraction; an electro-magnet being
so arranged as to attract the bob of the pendulum in both directions
alternately. In Mr. Bain's arrangement, the bob of the pendulum
is formed of a hollow coil of covered copper wire, which, on the
transmission of an electric current, becomes magnetic, and it is then
attracted by several permanent magnets fixed in a hollow horizontal
bar, over which the coil of wire moves. The accompanying diagram will
serve to explain more clearly the parts of the clock on which the
movement of the pendulum depends.

The pendulum rod, _B_, is made of wood, and the bob, _A_, consists of a
hollow coil of thick copper wire covered with cotton, through which the
hollow bar, _C C_, passes. Inside that bar there are several permanent
magnets, packed on each side of the ends of the coil of wire, the poles
of those on one side being the opposite of those on the other. In the
diagram only one magnet on each side is represented, _n_ and _s_, to
prevent confusion. The ends of the coil of wire are attached to the
pendulum rod, and they are conducted up it so as to form connection
with the wires of the voltaic battery, which are connected with gold
studs inserted into a horizontal stage fixed to the clock-case. A small
movable bridge, formed of wire, and having the ends tipped with gold or
platinum, rests upon the stage, and is shifted from side to side by the
pendulum. In these movements the gold points touch and slide over the
gold studs in the stage, and thereby make and break contact with the
voltaic battery, and alternately send and interrupt an electric current
through the coil of wire.

[Illustration]

Suppose, for instance, that the pendulum is about to rise to the right
towards _s_, at which time the voltaic circuit is completed. The coil
is, therefore, magnetic, and is attracted by the permanent magnet in
_C_. As the pendulum approaches the end of its swing, it pushes the
movable bridge away from the gold studs on which it rests, and thus
breaks connection with the voltaic battery, and the pendulum descends
unrestrained by the attractive force of the magnets. As the pendulum
descends towards its lowest point, it shifts the bridge on to the metal
studs on the other side, which are so disposed as to send a current
through the coil in a direction opposite to the former, so that the
poles of the voltaic battery are reversed, and the attractive force
is exerted in drawing the pendulum towards the left hand. In this
manner the power imparted to the coil, as the pendulum vibrates to and
fro, produces a continuous repetition of the attraction on each side
alternately, and maintains a constant action.

The only wheels required in a clock of this kind are those which turn
the hands; and the motion is communicated from the pendulum to the
seconds wheel by means of a small attached lever, working on a ratchet
wheel. The minute and the hour hands derive their movements from the
seconds wheel in the usual manner.

The voltaic battery employed to work Mr. Bain's clocks consists of a
pair of large copper and zinc plates buried in the moist earth, which
excite a sufficient amount of electricity to maintain the motion of the
pendulum. A battery of this kind will remain in action a long time, and
will serve to keep a clock going for several months. It is, indeed, a
near approach to the attainment of perpetual motion, since nothing but
the wearing away of the materials, or the accumulation of dust on the
connecting points, seems to prevent the realization of that mechanical
chimera.

There is a disadvantage attending the arrangement of Mr. Bain's
clocks, arising from the attachment of the pendulum to the wheels;
and as the moving force is derived directly from voltaic electricity,
any variation in the power of the battery causes variation in the
lengths of the vibrations, and produces irregularity. For the purpose
of remedying these defects, Mr. Shepherd, junior, has adopted an
arrangement which detaches the pendulum from the clock movement, and
makes its vibrations altogether independent of the varying force of
voltaic batteries.

In Mr. Shepherd's arrangement, the impulse of the pendulum is given
by successive blows from a spring, which is drawn back and then
liberated at each vibration. The hands of the clock are also moved
by electro-magnets, by which means the impelling forces and the
resistances encountered by the pendulum are always constant. By making
the pendulum thus independent of the works, and employing it merely to
make and break contract at regular intervals, any number of clocks in
the same establishment may be set in motion, and kept exactly together,
by a single pendulum.

The large clock over the principal entrance to the Great Exhibition was
on this construction. It would have been impossible, with any approach
to regularity, to have moved hands of that size, exposed as they
were to the wind, unless the pendulum had been independent of such
resistances.

Electro-Magnetic Clocks have not yet come into general use, partly
owing to imperfections in the battery connections, which occasionally
put a stop to their movements, but principally on account of the high
prices charged by the patentees. As no trains of wheels are requisite
in an Electro-Magnetic Clock, it might be manufactured very cheaply;
and when the price is reduced to its proper standard, and the trifling
practical defects are remedied, these clocks may possibly supersede
others.




ELECTRO-METALLURGY.


The electrotype, electro-gilding and plating, and the other
applications of the deposition of metals from their solutions, by
the agency of voltaic electricity, had their origin in the chance
observation of peculiarities in frequently repeated experiments. In
this, as in most other inventions, there are contending claimants for
priority; but there is little merit due to any of the first discoverers
of the process, who seem to have been guided altogether by accident. It
seems strange, now, on observing the extensive use that is made of the
deposition of metals, that it should have remained so long unapplied
after the principle had been known.

The "revivification," as it was called, of metals from their solutions
by voltaic electricity, was known at the beginning of the present
century; for, in 1805, Brugnatelli, an Italian chemist, gilded a silver
medal by connecting it with the negative pole of a voltaic battery,
when immersed in a solution of ammoniuret of gold. It did not occur to
him, however, that any use could be made of that mode of gilding, and
the experiment had no result.

Nothing further was done, even experimentally, towards advancing
the art of electrotyping, until Mr. Spencer, of Liverpool, when
experimenting with a Daniell's battery, in 1837, accidentally coated a
penny piece with copper; and when the thin sheet of metal was removed,
he found on it an exact counterpart of the head and letters of the
coin. Even this did not suggest any useful application; nor was it
until, by a further accident, a drop of varnish fell on the copper of
the negative pole, and showed that no deposition took place on the part
so covered, that the idea occurred to him of turning the deposition of
the copper to account. The method he adopted of doing so was to cover
a copper plate with varnish or wax, and to etch a design through the
covering. By then exposing the plate to the action of a solution of
sulphate of copper, when in connection with the negative pole of a
voltaic battery, the metal was deposited in the lines drawn through the
varnish, and a design in relief was fixed to the copper. This slight
advance in the art was not made known until it was announced, in 1839,
that Professor Jacobi, of St. Petersburg, had made application of
the same process. Mr. Spencer, indeed, was forestalled, even in this
country, by Mr. Jordan, a printer, who published an account in the
_Mechanics' Magazine_ for May, 1839, of a method of making copper casts
by the deposition of copper from its solution. In the autumn of the
same year, however, Mr. Spencer exhibited to the British Association
several more perfect specimens of electrotyping, that showed the
process might be rendered valuable; and from that time rapid progress
was made in bringing it into practical operation in a variety of ways.

The deposition of copper from its solution, when under the action
of voltaic electricity, is not produced by the decomposition of the
sulphate of copper, as might be supposed, but by the decomposition of
the water that acts as the solvent of the metallic salt. Thus, when
two platinum wires from the poles of a voltaic battery are introduced
into acidulated water, hydrogen gas is disengaged at the wire connected
with the negative pole, and oxygen at the other; but when a solution
of sulphate of copper is substituted for water, the hydrogen that is
disengaged combines with the oxygen that held the copper in solution,
and the metal is liberated. The copper thus liberated from its
combination with the oxygen is deposited, in a pure metallic state, on
the surface connected with the negative pole of the battery.

The simplest illustration of electro-metallic deposition is obtained
by immersing a silver spoon and a strip of zinc into a solution of
sulphate of copper. So long as the two metals are kept apart, no change
takes place on the silver, but on bringing them into contact, voltaic
action immediately commences, and a coating of copper is deposited
upon the spoon, and adheres firmly to the metal. If the action be
continued, and the supply of copper be maintained by the addition of
fresh crystals of the sulphate, the coat of copper may be increased in
thickness to almost any extent.

The first applications of the discovery were directed to the copying
of medals and coins. An impression of the metal was obtained in fusible
metal, which is an alloy composed of tin, lead, and bismuth, melted
together in the proportions of two of the latter to one each of the
former. This alloy expands on cooling, and thus affords a very sharp
impression of the medals; and as it melts at a low temperature, it may
be easily removed after the copper coating has been deposited upon it.

An electrotype mould, obtained directly from the medal, is, however,
more sharp in its definition than an impression, and is therefore
preferable, when circumstances admit of its being so taken. For that
purpose, the surface whereon the deposition is to be made is smeared
over with sweet oil, or with black lead. It is then carefully wiped
with cotton wool, but a minute quantity of the oil will still remain,
sufficient to prevent the metal from adhering.

A simple form of apparatus for the electrotype process is shown in the
accompanying diagram.

An earthenware jar, _a_, serves to hold the solution of copper, which
should be maintained in a saturated state by the addition of crystals
of the salt. A porous tube, _b_, holds a rod of amalgamated zinc, to
the top of which a binding-screw is soldered. The copper mould or
medal, _c_, is suspended in the solution by a wire, which is held
tight by the binding-screw, _d_. The porous jar is then filled to the
same height as the copper solution in the jar with diluted sulphuric
acid, in the proportions of one of acid to twenty of water. Voltaic
action immediately commences, and the copper will continue to be
deposited from the solution as long as the supply of fresh crystals
of sulphate of copper is continued. In about twenty-four hours the
coating of copper will be as thick as a thin card, and it may be then
removed. When detached from the medal, it will be found to be an exact
counterpart, in the minutest details, of the original; those parts of
the medal which are in relief being, of course, the reverse in the
mould.

[Illustration]

The extreme minuteness and delicacy of the electrotype process is
strikingly exemplified in its application to the transference of
engraved copper-plates. A highly finished engraved copper-plate
has a film of metal deposited over its whole surface, which, when
detached, exhibits all the lines that are cut into the copper-plate
in relief. That electrotype cast then serves as the mould for further
depositions, in which every line in the original engraving is so
perfectly developed, that it is impossible to detect a difference
in the impressions taken from the two plates. By this means any
number of casts may be made and worked from, whilst the original is
preserved uninjured. The objection to this application is that the
metal deposited is not so hard as the hammered plates, and will not,
therefore, bear the wear and tear of copper-plate printing so well as
the plates made by hand.

It was at one time supposed that the depositing of metal on surfaces,
by voltaic action, might be applied to the manufacture of numerous
kinds of copper articles without manual labour. For this purpose, casts
were made of plaster of Paris, which were covered with black lead,
to give them the property of conducting electricity, and the metal
was then deposited upon them. But, independently of the practical
difficulties attending the operation, it was found that the metal was
not sufficiently hard, and the cost of the requisite voltaic batteries
rendered the economy of the process questionable.

One of the successful applications of Electro-Metallurgy is founded
on the original application of it by Mr. Spencer. As already stated,
he covered metal plates with wax, and after scratching through the
coating, and exposing the metal, he submitted the plate to voltaic
action in a solution of sulphate of copper, and thus obtained a
representation, in relief, of the figures cut through the wax; but
he does not seem to have thought of the application of this mode of
deposition, since adopted, by which engravings in relief are obtained,
and printed from with the ordinary letter-press, in the same manner as
woodcuts. The name given to this new art is "Glyphography," and it is
used with great advantage when the effect of copper-plate engraving
is required; for cross lines, which are difficult to cut in wood, can
be worked by this method with as great facility as in copper-plate
etching.

Another application of Electro-Metallurgy that promises to be useful,
is the coating of glass and earthenware vessels with copper, so as to
enable them to be placed over the fire without being cracked. A glass
sauce-pan might thus be made, which, protected by metal covering,
would neither break nor crack when placed upon the fire, because the
metal would diffuse the heat over the whole surface, and prevent the
unequal expansion of the vessel, which is the cause of the cracking of
glass and earthenware when placed upon the fire. A patent was granted
last year for a mode of coating earthenware vessels with copper or
iron by electro-chemical deposition. The earthenware is first covered
either with copper leaf or with bronze powder, to obtain an electrical
conducting surface on which the copper can be deposited, and the
vessel is then placed in a solution of sulphate of copper, and put in
connection with the negative pole of a voltaic battery.

The electrotype is frequently applied with advantage to the
preservation and multiplication of objects of art and natural
productions, for even the forms of flowers may be in this manner
rendered durable; but the most important use that has been made of
the process is in plating and gilding. To effect that object, it is
necessary to employ a voltaic battery separated from the vessel in
which the decomposition takes place. The annexed diagram shows an
arrangement of this kind. A single cell of a Daniell's battery, _a_,
is connected by wires from its positive and negative poles, with metal
rods placed across the decomposition cell, _b_. The articles to be
plated are suspended by wires from the metal rod, _f_, and a plate of
silver is attached to the rod, _e_. Thus, when the vessel is filled
with the silvering liquid, a voltaic current is established, and the
deposition is effected on the articles connected with the negative pole.

[Illustration]

The menstruum best adapted for electro-plating is a solution of silver
in cyanide of potassium. During the process of deposition, the same
quantity of metal that is deposited from the liquid on the objects
connected with the negative pole of the battery is restored to it, by
dissolving an equal quantity from the silver plate connected with the
positive pole, and in this manner the solution is maintained at the
same strength. Any thickness of silver may be deposited by continuing
the process, but about one ounce and a half to a square foot of
surface is considered a full quantity. Those parts on which no silver
is required to be deposited are covered with varnish or wax, which
protects them from the voltaic action.

Where the operation of electro-plating is carried on extensively,
decomposing troughs, holding nearly 300 gallons, are employed, and the
silver plates in a single trough expose a surface of thirty square feet
to the dissolving action of the menstruum under the influence of the
voltaic battery.

By the aid of electro-plating the most elaborate designs of the artist
in metal can be covered with silver on every part; and a group, finely
engraved in copper, may be made to resemble in every particular a work
cut out of solid silver. The metal is usually deposited in a granulated
state, resembling "frosted" silver, and the parts required to be bright
are subsequently burnished; but by the addition of a few drops of the
sulphuret of carbon to the solution, the silver may be precipitated
perfectly bright.




GAS LIGHTING.


The invention of Gas Lighting had its origin in the earliest times of
history; not, indeed, as we now see it, burning at the end of a pipe
supplied with gas made artificially, and stored in gas-holders, but
blazing from fissures in the ground, supplied from natural sources in
the bowels of the earth. The Greek fire-altars are supposed to have
been supplied with gas, either issuing from bituminous beds, or made
artificially by the priests, by pouring oil on heated stones placed
in cavities beneath. Fountains of naphtha, and fires issuing from the
earth at Ecbatana, in Media, are mentioned by Plutarch in his life of
Alexander, and many other ancient historians record the knowledge of
similar instances of natural gas lighting.

In later times, the inflammable gas issuing into the galleries of coal
mines, and either exploding when mixed with atmospheric air, or blazing
as it issued from fissures in the coal, afforded instances of the
natural production of gas, the ignition of which too frequently proved
fatal to those in the mines.

A remarkable instance of the issue of inflammable gas into the shaft of
a coal mine at Whitehaven, which produced a blaze about 3 feet diameter
and 6 feet long, is noticed in the "Philosophical Transactions" of
1733. The part whence the gas issued was vaulted off, and a tube was
inserted into the cavity and carried to the top of the pit, where it
escaped in undiminished quantity for years, and lighted the country for
a distance of several miles. Many experiments were made with this large
issue of gas, and it was proposed to conduct it in pipes to Whitehaven,
to light the streets of that town, but the proposition was rejected by
the local authorities.

In China, naturally produced gas is used on a large scale, and was so
long before the knowledge of its application was acquired by Europeans.
Beds of coal, lying at a great depth, are frequently pierced by the
borers for salt water, and from these wells the inflammable gas springs
up. It sometimes appears as a jet of fire from 20 to 30 feet high; and,
in the neighbourhood of Thsee-Lieon-Teing, the salt works were formerly
heated and lighted by means of these fountains of fire. Bamboo pipes
carry the gas from the spring to the places where it is intended to be
consumed. These canes are terminated by tubes of pipe-clay, to prevent
their being burnt, and other bamboo canes conduct the gas intended
for lighting the streets, and into large apartments and kitchens.
Thus Nature presents in these positions a complete establishment of
gas-light works.[9]

Though the production of illuminating gas from natural sources had
been thus long known, the idea of distilling it artificially from
coal, for the purpose of illumination, did not occur until the end of
the last century. Dr. Clayton, indeed, nearly arrived at the practical
application of carburretted hydrogen, in 1737, for he instituted
experiments to prove that coal contains gas, nearly similar to that of
the "fire damp" in coal mines, and that it burns with a bright flame.
At that time, however, the nature of gases was so imperfectly known,
that he was unable to do more than discover that coal possesses the
property of giving out, when heated, gas that will burn with a bright
light.

In the "Philosophical Transactions" of 1739, Dr. Clayton thus
describes the effect of the "spirit of coal," obtained by destructive
distillation in an iron retort. "I kept this spirit," he says, "in
bladders for a considerable time, and endeavoured several ways to
condense it, but in vain; and when I had a mind to divert strangers or
friends, I have frequently taken one of these bladders, and pierced
a hole in it with a pin, and, compressing gently the bladder near
the flame of a candle till it once took fire, it would then continue
flaming till all the spirit was compressed out of the bladder; which
was the more surprising, because no one could discern any difference in
the appearance between these bladders and those which were filled with
common air."

The first known application of coal gas to illumination was made, in
1792, by Mr. William Murdoch, engineer at the Soho manufactory, to
whose great ingenuity the world is also indebted for the invention of
the first plan of a steam locomotive engine.[10] He was at that time
occupied in superintending the fitting up of steam engines for the
Cornish mines, and his attention having been directed to the properties
of gas issuing from coal, he instituted a series of experiments on
carburretted hydrogen, the practical result of which was the lighting
of his house and offices, at Redruth, with coal gas. The mines at which
Mr. Murdoch worked being some miles distant from his house, he was in
the constant practice of filling a bladder with coal gas, in the neck
of which he fixed a metallic tube with a small orifice, through which
the gas issued. The lighted gas issuing through the tube served as a
lantern to light his way; and as he thus proceeded along the road with
the light issuing from the bladder, the country people looked upon him
as a wizard.

The gas was generated by Mr. Murdoch in an iron retort, and collected
in a common gasometer, from which it was conducted in pipes to the
rooms to be lighted. He also, in an early stage of the invention,
contrived a means for making the gas portable, by compressing it into
strong vessels; a plan which, a few years since, was adopted by the
Portable Gas Company in London.

Mr. Murdoch having proved the practicability of illumination by gas
generated from coal, he continued his experiments to facilitate the
manufacture of the gas on a large scale, and for its more perfect
purification. The first public display of its illuminating power was
made at the rejoicings for the peace of Amiens, in 1802, on which
occasion part of the work-shops of Messrs. Boulton and Watt, at Soho,
was brilliantly illuminated with coal gas by Mr. Murdoch. In 1805,
Messrs. Phillips and Lee, of Manchester, had their extensive cotton
mill fitted up with gas apparatus, under the superintendence of Mr.
Murdoch, and the quantity of light given out by the burners in all
parts of the cotton mill was equal to that of 3,000 candles.[11]

Notwithstanding these eminently successful trials of gas lighting,
the prejudice against innovation prevented, for several years, the
extensive adoption of the plan. As every establishment using gas had
to make it, and as the apparatus was costly and imperfectly managed,
the expense in the first instance, the trouble, and the noxious
smell, presented great obstacles to the introduction of that mode of
illumination. The popular notion, also, that streams of flame were
rushing along the pipes produced an impression that gas lighting must
be very dangerous, which it required time to disprove. It was not,
therefore, till several years after the advantages and economy of gas
had been practically established, that a public company was formed
for laying down pipes to light the streets, and to convey the gas into
houses for lighting shops.

The person to whom the world is chiefly indebted for the practical
application of gas lighting is Mr. Winsor, who had been a merchant in
London. Being very sanguine as to the advantages to be derived from
gas lighting, and possessing an ardent temperament which no opposition
could quench, he undertook to introduce it to public notice, and to
form a company for lighting the whole of England with gas. He hired
the old Lyceum Theatre, which he lighted with coal gas, and he there
delivered lectures and exhibited experiments to show the benefits that
would arise from the universal use of gas light, and coke fuel. He
published an extravagant prospectus of a company to be formed, with the
following title:--"A National Light and Heat Company, for providing our
streets and houses with light and heat, on similar principles as they
are now (1816) supplied with water. Demonstrated by the patentee at No.
97, Pall Mall, where it is proved, by positive experiments and decisive
calculation, that the destruction of smoke would open unto the empire
of Great Britain new and unparalleled sources of inexhaustible wealth
at this most portentous crisis of Europe. The serious perusal of this
publication, and an attentive observation of the decisive experiments,
will carry conviction to every mind."

In this prospectus Mr. Winsor attempted to make it appear that by
adopting his plan there would be "a grand balance of profit for the
whole realm of £115,000,000," and each shareholder of the company was
promised, "at the lowest calculation, £570 for every £5 deposit." He
entertained the notion of making the use of gas and coke compulsory, by
levying a tax on all who obstinately refused to adopt what would be so
much to their own advantage. This tax, he said, "cannot be oppressive
in the least, because it falls on the obstinate only, who shall resist
the use of a far superior, cheaper, and safer fuel." Not content with
the language of prose, Mr. Winsor vented his thoughts and feelings in
numerous poetical effusions. The flights of his Muse, however, were not
into the regions of sublimity, as may be perceived by the following
specimen:--

      "Must Britons be condemned for ever to wallow
      In filthy soot, noxious smoke, train oil, and tallow,
      And their poisonous fumes for ever to swallow?
      For with sparky soot, snuffs and vapours, men have constant
              strife,--
      Those who are not burned to death are smothered during life."

Mr. Winsor's absurd statements--in the truth of which he potently
believed--and the wild, random manner of making them known, excited
much ridicule and opposition. Among his opponents was Mr. Nicholson,
the editor of the _Chemical Review_, who not only challenged Mr.
Winsor's estimates, but the validity of his patent, on the ground
that Mr. Murdoch was the original inventor. Mr. Winsor's plans and
calculations were burlesqued in a cleverly written "Heroic Poem,"
published in a quarto volume, which, whilst professing to extol the
virtues of gas and coke, quizzed its hero most unmercifully. The poem
concluded with this address:--

      "And when, ah, Winsor!--distant be the day!--
      Life's flame no longer shall ignite thy clay,
      Thy phosphur nature, active still, and bright,
      Above us shall diffuse _post obit_ light.
      Perhaps, translated to another sphere,
      Thy spirit--like thy light, refined and clear--
      Ballooned with purest hydrogen, shall rise,
      And add a PATENT PLANET to the skies.
      Then some sage Sidrophel, with Herschel eye,
      The bright _Winsorium Sidus_ shall descry;
      The _Vox Stellarum_ shall record thy name,
      And thine outlive another Winsor's fame."

"Though we may smile at Mr. Winsor's extravagant plans and
calculations," observes the _Journal of Gas Lighting_, "we cannot but
admire the enthusiasm with which he pursued his object, and ultimately
succeeded in establishing the first gas company. The lighting of Pall
Mall with gas, in the spring of 1807, gave increased stimulus to the
project, and application was made to Parliament to carry it into
effect. The bill was opposed by Mr. Murdoch and thrown out; but in
the following year (1810) the application was successfully renewed.
The scheme, however, as sanctioned by Parliament, was sadly shorn
of its magnificent proportions; and, instead of a 'Grand National
Light and Heat Company, for Lighting and Heating the Whole Kingdom,'
its operations were limited to London, Westminster, and Southwark;
nor were any special taxes imposed on those who should obstinately
refuse to use the light and burn the coke. The Chartered Gas Company,
established by Mr. Winsor's persevering efforts, has served as the
guiding star to all other gas companies in the world."

The illuminating property of coal gas depends on the quantity of carbon
it contains. Pure hydrogen gas burns with a pale blue flame that gives
scarcely any light, though it possesses intense heating power. If,
however, minute particles of a solid body--powdered charcoal, for
instance--be thrown into the flame, they become white-hot, and the
incandescence of those solid particles produces a brilliant light. The
same effect is caused by the combustion of the carburretted hydrogen
gas, and in a more perfect manner. That gas contains a large portion
of carbon in a state of vapour, and when a light is applied to a jet
of the gas the hydrogen immediately inflames, the carbon is deposited
in the flame, and the minute particles into which it is disseminated
become highly heated and ignite.

There are two distinct states of carbonization in illuminating gas.
The commoner kind--the ordinary coal gas--consists of two measures
of hydrogen mixed with one measure of carbon vapour. The specific
gravity of such gas is about one-half that of atmospheric air, and
it is eight times heavier than pure hydrogen.[12] The best kind of
gas for illumination is obtained from the distillation of oil. It is
called olefiant gas, and contains equal measures of hydrogen gas and
carbon vapour; its specific gravity is 0.985, being about fifteen times
heavier than pure hydrogen.

The _rationale_ of the process of making coal gas consists in expelling
the volatile matters from the coal by heat, in closed vessels or
retorts, and then separating the gas and purifying it on its passage
from the retort to the gas-holder, where it is stored for use.

The retorts are usually made of cast iron, and are about 7 feet long,
14 inches in depth, and the same in width; the shape being that of
an arch. The retorts will hold two hundredweight of coal each, but
they are never filled, because during the process of distillation the
carbonaceous part of the coal expands, and occupies more space than
the original quantity, the proportion of expansion being as one and a
quarter to one. There is a large aperture for the admission of coal
and the extraction of coke, which aperture is covered with a lid, and
screwed to make it air-tight. A tube is inserted into the mouth of the
retort, to carry off the products of the distillation. That tube rises
about twelve feet, and then dips into a large horizontal pipe, one foot
in diameter, called the hydraulic main, in which are collected the
tar and ammoniacal liquor that distil from the coal. Ten or fourteen
retorts are usually set back to back in brickwork, to be heated by one
fire; but the plan has been recently introduced of employing long clay
retorts, which are charged at both ends. These are found to possess
considerable advantage over iron, not only from their lower price, but
from the facility with which the carbonaceous deposit is removed, and
the full charges worked off. Coke is generally burned in the furnaces,
and the heat is continually maintained so as to keep the retorts
red-hot.

As atmospheric air cannot gain access to the coal in the retorts, the
gases expelled do not inflame, nor can the parts that are not volatile
be consumed without a supply of air. It is entirely a process of
distillation, in which all the products can be collected. The volatile
parts are carried off by the pipe, and the solid carbonaceous matter,
or coke, is left in the retort.

The first effect of heat on coal, after it is put into the retort,
is to expel the moisture, which, in combination with the air, issues
in the form of steam. Tar then distils, with some portions of gas,
consisting of hydrogen and ammonia. When the retort has attained a
bright cherry-red heat, the disengagement of the carburretted hydrogen
is most active; and it is found that the more quickly the coal is
heated, the greater is the quantity of illuminating gas generated.

The production of coal gas, and the development of its properties at
different stages of distillation, may be readily shown by means of
a common tobacco pipe. Fill the bowl of the pipe with small pieces
of coal, cover it over with a lump of clay, and then put it into a
hot fire, with the stalk of the pipe projecting through the bars.
Presently steam will be seen to issue from the pipe, and afterwards
smoke, and, if a light be applied, a jet of flame will issue forth, the
brilliancy of which will increase as the bowl of the pipe becomes more
heated, until the best part of the gas has been distilled from the coal.

The gas is mingled with various volatile products as it issues from
the retort, and requires to be purified before it is fitted for
illumination. The most abundant matter that passes over with it is tar.
The vapour of that substance, however, condenses when cooled, and it
may thus be separated from the gas very effectually. For that purpose
the gas, after having deposited a large portion of the tar in the
hydraulic main, is made to traverse through a number of vertical pipes,
and in passing through them a further quantity of tar, accompanied by
ammoniacal liquor, is deposited, and collected in a reservoir at the
bottom. The next process is the purification of the gas from carbonic
acid and sulphuretted hydrogen. This is commonly done by passing it
through water and lime; the combination of the carbonic acid with the
lime being facilitated by agitation. The method of purifying by lime
was introduced by Mr. Clegg; and by a later process, oxide of iron is
used to absorb the sulphuretted hydrogen. The gas, when purified, is
conveyed to the gas-holder, whence it is forced by pressure into the
mains and pipes.

An apparatus for generating coal gas on a small scale for private
establishments, remote from sources of ordinary supply, is represented
in the accompanying woodcut. The retort, A, is fitted in a small
furnace. The coal is put in at F, and the products of distillation pass
through the bent pipe, E. The more liquid portions of the tar pass at
once through the tube, B, into the receiver, G; and as the gas passes
along the bent tube, C, it becomes cooled, and a further deposit of tar
and ammoniacal liquor is made. The gas is then conveyed along another
tube into the purifier, H, filled with lime and water, and it thence
passes into the gas-holder. Tubes are inserted into the latter for
conveying the gas to the burners.

[Illustration]

The quantity and the quality of the gas yielded by coal differ
materially according to the kind employed. One ton of good Newcastle
coal will yield 9,500 cubic feet of gas, which, when burnt in the
best manner, gives a light equal to that of 422 lbs. of spermaceti
candles. One ton of Wigan cannel coal yields 10,000 cubic feet, and
gives a light equal to 747 lbs. of spermaceti candles.[13] The price,
in London, of good gas from Newcastle coal, is 4s. 6d. per thousand
cubic feet, which gives a light equal to 74½ lbs. of spermaceti, and
equal to 89 lbs. of mould candles; therefore, when the latter are 8d.
a pound, the burning of gas is twelve times more economical than the
burning of candles. In Liverpool, gas from cannel coal is supplied at
the low price of 3s. 9d. per thousand feet; and that gas gives at least
one-third more light than the ordinary London gas.

The cleanliness of gas, as compared with candles or oil, is a
further recommendation; and for the purpose of lighting streets,
shops, factories, public buildings, and halls, it presents important
advantages; but it is not well adapted for small sitting rooms, because
the heat of the flame makes it unpleasant and injurious to the eyes
when near, and, unless very pure, it deteriorates the air of closed
apartments. In many parts of the country, however, where coals are
cheap, and the price of gas is consequently less than in London, it is
introduced into every room of nearly all private houses.

The best kind of gas made from mineral substances is produced by the
distillation of a bituminous shale, called Boghead coal, which was
discovered a few years since in Scotland. One ton of this material
yields 15,000 cubic feet of gas, which is equal in illuminating power
to 1,930 lbs. of sperm candles. Boghead coal is now commonly used
for mixing its gas with that of inferior quality, to bring up the
illuminating power to the required standard.

Olefiant gas, made from oil, burns with a brighter and purer light
than common coal gas, but it is more costly. It is made nearly in the
same manner, by distillation in retorts; the principal difference
consisting in the degree and regulation of the temperature. A dull red
heat is the best, and in order to keep the oil exposed to the action
of an invariable heat, it is admitted gradually into the retorts, into
which pieces of brick or coke are inserted to increase the heating
surface. One pound of common oil yields about 15 feet of olefiant gas.
The same kind of gas may also be obtained in smaller quantities by the
distillation of tar, rosin, or pitch. Twelve cubic feet of gas may be
obtained from one pound of tar, and ten from the same weight of rosin.

The brilliancy of gas-light depends, in some measure, on the kind of
burner employed. To obtain a steady light, an argand burner is usually
adopted; the gas being allowed to escape through a number of minute
holes pierced in a hollow ring of metal, which admits a current of
air through the middle. To increase the supply of air, the burner is
covered with a glass chimney, which, if not too long, adds to the
brilliancy of the flame; but a very long chimney produces so strong a
current of air, as to cool the flame, and diminish the light. A plan
is sometimes adopted of placing a small metal disc a short distance
above the jets, so as to spread the flame. By this means the brightness
is increased, by exposing the flame more directly to the current of
air; and the metal disc, by becoming heated, also tends to aid the
combustion of the carbon.

One of the problems to be solved on the original formation of gas works
was the size of pipes, and the amount of pressure required to force the
gas to the various burners. It was at first supposed that the friction
against the pipes would oppose so much resistance to the passage of the
gas, that it could not be transmitted to great distances. It was found,
however, that the perpendicular pressure of a few inches of water was
quite sufficient to force the gas through the mains and small pipes of
an extensive range of streets. A bold attempt was made at Birmingham,
in 1826, to bring gas from the collieries, at a distance of ten miles
from the town. The plan was laughed at by many as impracticable, but it
was attended with complete success. The gas being made near the mouth
of the coal-pit, the cost of conveyance was saved by the additional
outlay in the first instance. It must be observed, however, that it
is extremely difficult in practice to avoid the escape of gas at the
junctions of the pipes; and by increasing the length of the gas mains,
the greater will be the leakage. The loss from this cause, in some gas
works, exceeds 20 per cent. of the gas manufactured.

The volume of gas discharged from a pipe is directly proportional to
the square of its diameter, and inversely as the square of its length.
Thus, if a pipe required to discharge 250 cubic feet of gas in an hour,
at a distance of 200 feet, must have an internal diameter of 1 inch;
to discharge 2,000 feet in an hour, at a distance of 1,000 feet, would
require a diameter of 4·47 inches. The same quantity discharged at
double the distance would require a pipe 5·32 inches in diameter; at a
distance of 4,000 feet the diameter must be increased to 6·13 inches;
and at a distance of 6,000 feet the diameter should be 7 inches.

On the first introduction of gas-light, the companies who supplied
it charged a fixed sum for each burner of a given size. This mode of
charging was, however, very unsatisfactory, for the size of the burner
is a very uncertain indication of the quantity of gas consumed. Persons
using gas desired to pay for the quantity they actually burned; and
to enable them to do this, a special contrivance was invented by Mr.
Clegg, the engineer of the Chartered Gas Company, called a gas-meter.
That instrument measures, with sufficient accuracy for practical
purposes, the volume of gas that passes through it to the burners, and
thus each consumer of gas now pays only for the number of cubic feet
consumed.

The accompanying diagrams represent sections of a gas meter, as seen
in front and edgewise. The outer case of the instrument, which is a
flat cylinder made of sheet iron, is indicated by the letters _c_, _c_.
Inside it there revolves another cylinder, made also of thin sheet
iron, and divided into four compartments, marked _d_, _d_, _d_, _d_.
This interior cylinder readily revolves on an axis, _g_, _g_, shown in
the section of the instrument as seen edgewise. The gas enters from
the street pipe through the opening, _a_, and it is forced out to the
burners through the pipe, _b_, the latter being seen in the narrow
section only. In that diagram, also, there is shown a cog-wheel, _h_,
fixed on to the axis, and a small outer case, in which that wheel
rotates. Water is poured into that external case until the gas-meter is
rather more than half filled, the level of the water being shown at _i_.

[Illustration]

The action of the instrument will be readily understood by examining
the two sections. The gas, on entering the tube, _a_, presses against
the upper surface of the compartment that happens to be then above it,
and tends to turn the inner cylinder round. This pressure forces the
gas through the opening, _b_, to the burner; and as the compartment
then in communication with that opening is emptied of the gas it
contains, in the direction of the arrow, it is gradually forced under
the level of the water, and the other compartment, which has in the
meantime been filling with gas, continues the supply. Thus, supposing
each division of the inner revolving cylinder to hold 108 cubic
inches, a complete revolution would indicate that the fourth part of a
cubic foot had passed through the pipe, _b_, to the burners. Several
cog-wheels, arranged like clock-work mechanism, are connected with
the wheel, _g_, and by this means the number of cubic feet of gas
consumed is indicated by hands fixed to the wheels, and pointing to the
corresponding figures on a series of dials.

Some inconvenience and irregularity having been experienced in the
use of the wet meter, the correctness of which, it is evident, may be
affected by variations in the height of the water level, dry meters
have been constructed for measuring gas, by causing it to pass through
a small expanding chamber, similar in principle to a pair of bellows.
The objection to these instruments is that the leather, or other
flexible substance that forms the sides of the expanding chambers,
becomes rigid by use, and the valves are liable to get out of order;
but in the last improvement of the instrument, by Mr. Croll, these
objections are stated to be effectually removed.

Numerous attempts have been made to produce illuminating gas from other
substances than coal, but without advantage. The plan that promised the
most success was the production of hydrogen gas by the decomposition
of water, which was passed over heated coke in retorts, and by that
means the oxygen of the water, combined with the incandescent coke and
the hydrogen, was set free. The gas thus collected possessed little
illuminating power, but it was afterwards mixed with the rich gas from
cannel coal, and raised to the requisite illuminating standard. It was
found, however, in practice, that the compound gas thus formed was more
costly than ordinary coal gas, and the plan has been discontinued.
Another method of giving illuminating power to water gas was to
surround the flame with platinum gauze, which was rendered incandescent
by the heat, and became highly luminous. But it required twice the
quantity of gas burned in this manner to produce a light equal to that
of carburretted hydrogen, and the combustion of so much hydrogen gas
produced an amount of vapour and heat that were very unpleasant. That
mode of gas illumination, called the "Gillard light," from the name
of the inventor, was also found more costly than the ordinary mode of
lighting with coal gas, which has now no rival to compete with it in
economical illumination.

No Act of Parliament is now required, as originally proposed by
Mr. Winsor, to enforce the burning of coal gas. Its advantages, in
point of economy, cleanliness, and even of safety, are sufficiently
understood to spread the use of coal gas to every part of the kingdom.
In the metropolis alone there are twelve gas companies, who receive
for the sale of gas an average of £100,000 per annum each, thus making
the sum paid for gas lighting in London £1,200,000, and it has been
estimated as high as £2,000,000. Taking the average price to be 4s.
6d. per thousand cubic feet, the quantity of gas consumed amounts
to 5,300,000,000 cubic feet; and if we add to that quantity 20 per
cent. for leakage through the mains and pipes, the quantity of gas
manufactured in the metropolitian gas works is upwards of 6,000,000,000
cubic feet in a year. It may, perhaps, give a clearer notion of this
immense quantity to say, that a gas-holder, capable of containing it,
would require to be one mile in diameter, and the height of St. Paul's
Cathedral. The light produced by burning such a volume of gas would
be equal to that of 150,000 tons of mould candles, which would cost
£13,000,000. The quantity of coals requisite for the production of the
gas manufactured annually in London is upwards of 600,000 tons.




THE ELECTRIC LIGHT.


The Electric Light is the brightest meteor that has flashed across the
horizon of promise during the present century. When first exhibited
as a means of illumination, about twelve years ago, the splendour of
the rays emitted, and the delusive representations of the small cost
required to produce such a brilliant light, led the public to believe
that the career of gas-lighting was drawing to a close, and that night
would be turned into day by this wonderful demonstration of electrical
power. The light produced by charcoal points, subjected to the action
of a powerful voltaic battery, was, however, no novelty at that time;
for as far back as 1810, Sir Humphry Davy was accustomed to exhibit
that development of electrical force at the Royal Institution, and it
formed a standard experiment in most chemical lectures. But it seems
not to have been thought applicable in those days to the purposes of
illumination; and when Mr. Staite brought it into notice, and exhibited
its effects on the tops of some public buildings, it was considered one
of the most wonderful inventions of the age.

Mr. Staite's patent, taken out in 1847, though commonly supposed to
be for the Electric Light generally, was limited in its clauses to
the construction of a voltaic battery and apparatus, adapted for
maintaining constancy, and for giving steadiness to the light. The
merely temporary continuance of the _voltaic arc_, as it was formerly
called, seemed indeed to preclude the possibility of its adoption as a
means of illumination; it was therefore a great point gained to give
stability and constancy to the light. The difficulty of accomplishing
this will be perceived when it is known that the charcoal points,
between which the action takes place, are constantly undergoing change,
the particles of carbon being transferred from one to the other. There
is no actual combustion of the charcoal, in the ordinary meaning of
the term; the action is principally confined to the transfer of the
charcoal connected with the positive pole, to that connected with the
negative pole of the voltaic battery, a hollow being formed in one, and
a pyramidical accumulation of particles in the other. This action was
beautifully shown by Professor Faraday at the Royal Institution last
year, by projecting the image of the charcoal points on to a screen,
by means of the Electric Light itself. The image, magnified by the
lenses of the electric lamp, could thus be distinctly seen without
being too brilliant to dazzle the eyes. The particles of carbon, heated
to whiteness, were perceived to be in active motion, and the piling
up of the pyramid in one, and the hollow produced in the other, were
continually varying the distances between them, and thus tending to
cause unsteadiness in the light.

Numerous contrivances have been adopted for the purpose of keeping
the points at exactly the same distance, as the want of stability was
supposed to be the only obstacle to the adoption of the Electric Light.
These contrivances have so far succeeded, that a tolerably steady light
can be maintained for some time, but under the most careful management
the points occasionally approach too near or are too far apart to
maintain an equable light.

Among other inventions to increase the steadiness of the light is one
that was patented in 1856, by Mr. Way, in which mercury is substituted
for charcoal, but the steadiness of light to be thus acquired must
be attained with a great loss of illuminating power, and the vapour
arising from the combustion of the mercury would be extremely injurious
to health.

Mr. Hearder, of Plymouth, has produced more brilliant effects with the
Electric Light than any other person. Some remarkable exhibitions of
the power of the light were made by him, in April, 1849, from the top
of the Devonport Column, and several scientific gentlemen undertook to
make observations at different localities to a distance of five miles.
At Tremeton Castle, on the banks of the Tamar, a distance of nearly 3½
miles; the light cast a strong shadow, and writing could be distinctly
read by it. The space illuminated was at least three quarters of a
mile broad. To aid the effect, a reflector was employed, and when the
rays were directed to the clouds, they had the appearance of a huge
comet, the reflector being the nucleus. The intensity of the light was
ascertained to be equal to that of 301,400 mould candles of six to the
pound, whilst the light of the Breakwater Lighthouse was equal to only
150 candles. At a distance of five miles the light was sufficiently
powerful to enable persons to read a book.

The battery employed by Mr. Hearder in these brilliant experiments
consisted of 80 cells of a Maynooth battery, 4 inches square, and
the carbon cylinders between which the light appeared were formed of
powdered coke, mixed with tar, and rammed into a tube three quarters
of an inch in diameter. When these cylinders are about a quarter of
an inch apart, the Electric Light appears at the end of each for the
space of more than half an inch. The light, during the experiments at
Plymouth, was maintained for three hours, and the materials employed
amounted to one pound and a-half of zinc, 114 fluid ounces of sulphuric
acid, the same quantity of nitric acid, and six pounds of muriate of
ammonia.[14]

The most serious practical objection to the introduction of the
Electric Light, as a means of general illumination, is its expense.
When the project was first brought into notice, attempts were made to
show that the battery power required might be obtained at little cost,
and in this respect some deceptions were practised not creditable to
the parties engaged in promoting the scheme. It has been proved by Mr.
Grove that the cost of ordinary batteries necessary to maintain the
light in full brilliancy would greatly exceed the price of an equal
light from gas.

A plan was patented for generating the required voltaic power, free
from cost, by applying the residual sulphate of zinc as paint, and an
Electric Power and Light Company was formed to carry out the project.
But the plan failed, and the affairs of the company have recently been
"wound up."

Until some cheaper mode of generating electricity than is at present
known be invented, there is no hope of the Electric Light becoming
generally available, but there are special circumstances in which
it may be applied with advantage. It is peculiarly applicable for
lighthouses, as its rays would penetrate through a foggy atmosphere
that would obscure the light of ordinary flames, and in such cases the
extra cost should not operate as an obstacle to its use.




INSTANTANEOUS LIGHTS.


Those who are not old enough to remember the time when flint-and-steel
were the implements employed to obtain a light, can have no sufficient
appreciation of the great convenience of "Lucifer" matches. In those
"good old times," it was a regular household care to provide a
sufficiency of tinder, to see that it was kept dry, and that there
was a proper flint "with fire in it." The striking of a light, when
the tinder-box was adequately supplied, was no mean accomplishment;
and the unskilful hand, operating in the dark, would either get no
sparks at all, or send them in a wrong direction, and not unfrequently
strike the skin off the knuckles, in the vain endeavour to set light
to the tinder. Or if the tinder were damp, the sparks would fall upon
it without igniting, and minutes would be spent in holding a pointed
brimstone match to the delusive spark, and blowing at it without
effect. Sometimes the incautious operator, tired with his fruitless
efforts, would sprinkle gunpowder over the tinder, to make it take
fire more readily, and whilst puffing at a long-desired spark, the
gunpowder would explode in his face and nearly blind him. Such were
some of the annoyances, attended by loss of time, that were experienced
in obtaining the same result that is now produced instantaneously, and
much more effectively, by merely rubbing the match against any rough
surface.

Several attempts had, indeed, been made many years ago to supplant
the flint-and-steel and tinder-box, and some of the plans adopted so
closely approach the matches now in use, that we wonder the inventors
did not succeed long since in contriving the very facile means of
striking a light that we now enjoy. Phosphorus and brimstone matches
were first employed for the purpose. The phosphorus was contained in a
bottle placed within a tin case, which also held the pointed brimstone
matches and a piece of cork. The match was dipped into the phosphorus
bottle, and then rubbed on the cork; and the friction excited
sufficient heat to inflame the small quantity of phosphorus adhering
to the match and, to set fire to the sulphur. These phosphorus boxes
answered the purpose very well, but the apprehended danger of using so
inflammable a substance prevented their coming into general use; and
they were much more costly than a tinder-box.

In the next advance, if it may be so called, in the invention of
instantaneous light-producers, phosphorus was altogether discarded,
and a mixture of chlorate of potass, then called oxymuriate of potass,
and sugar was employed. Those substances, when combined, inflame
explosively in contact with sulphuric acid. In applying them for the
purpose of obtaining instantaneous light, they were mixed together in
an adhesive menstruum, into which the ends of small rectangular matches
were dipped. These matches very nearly resembled the "Lucifers" of
the present day. To ignite them, a small bottle containing sulphuric
acid and asbestos was provided, and they were arranged together in
an ornamental taper-stand for the chimney-piece. This apparatus was
not received with much favour, partly on account of injury done by
a careless use of the sulphuric acid, partly because it failed to
act when the acid had absorbed moisture from the atmosphere, but
principally because of its cost.

To obviate the objection arising from the use of sulphuric acid in
open bottles, an ingenious contrivance was adopted, by which each
match contained its own reservoir of acid sufficient for igniting
the inflammable compound. Small glass globules, containing sulphuric
acid, were introduced into the composition of chlorate of potass and
sugar, which, when broken, set fire to the mixture and lighted the
match. These instantaneous lights, which were called _Prometheans_,
were more ingenious than useful, because the trouble of manufacture
rendered them expensive, and the sulphuric acid was more likely to
injure furniture in that form than when a bottle with asbestos was
used. The Prometheans, however, possessed the advantage of portability,
and for occasional purposes they were convenient. In some of the forms
in which the Prometheans were manufactured, the glass globule of acid,
surrounded by its inflammable compound, was attached to the end of a
small stick of sealing-wax, sufficiently large to seal a letter; but
this refinement in instantaneous lights was not much patronized.

Notwithstanding these ingenious attempts to produce light by chemical
action, the flint-and-steel retained possession of the field until
a match was made that ignited by friction alone. The first kind of
friction match was invented in 1832. It consisted of a thin splinter
of dried wood, the top of which was dipped in a mixture of one part
of chlorate of potass, two of sulphide of antimony, and one of gum.
To ignite the match it was necessary to draw it briskly through
sand-paper. These matches required some address to light them, because
much more friction was required than is sufficient to light Lucifers.

The next improvement was the "Congreve" match, in which recourse
was had to the materials previously used, separately, for obtaining
instantaneous lights. Congreve matches were composed of an emulsion
of phosphorus mixed with chlorate of potass, into which the matches,
previously tipped with sulphur, were dipped. These matches were of
the same size and form as the Lucifers now in general use, and they
ignited readily by friction on sand-paper or other rough surface. Their
explosive noise on inflammation, which gave them their name, was the
only apparent difference between Congreves and Lucifers, and their
introduction completely supplanted the flint-and-steel.

The noiseless match, or Lucifer, has, in its turn, driven the Congreve
almost out of use, though for practical purposes the latter was as
effective, and it was less dangerous. The Lucifer matches depend
altogether on phosphorus for their inflammability. Their composition
is an emulsion of phosphorus with glue, nitre, and some colouring
matters. The sulphur matches, after having been tipped with that
composition, are exposed in a warm room until a sufficient quantity of
the phosphorus is evaporated by slow combustion, to leave a film of
glue on the surface to protect the remainder from the action of the
atmosphere. The usual proportions for the compound are, phosphorus
four parts, nitre ten, glue six, red ochre five, and smalt two. The
principle on which the action of Lucifer matches depends, is the strong
affinity of phosphorus for oxygen, of which the nitre with which it
is mixed contains an abundant supply; and by drawing the match across
sand-paper, sufficient heat is excited by the friction to ignite
the phosphorus, and the nitre supplies the oxygen to maintain rapid
combustion.

The manufacture of Lucifer matches is conducted on a very large scale
in this country and on the Continent. It requires several ship loads of
wood to supply the requirements of Lucifer-match makers; and ingenious
contrivances have been patented for cutting it up into splints of the
proper size. For that purpose, after the wood has been reduced to
the required lengths by circular saws, it is cut up into splints by
a number of lancet points, separated from each other as far apart as
the thickness of a match, which pass over the wood and divide it with
great rapidity. The splints are collected into bundles of one thousand,
and each end having been dipped into melted sulphur, they are divided
in the middle by a circular saw.

The Reports of the Juries of the Great Exhibition supply a variety of
statistical details respecting the manufacture of chemical matches,
from which it appears that the quantity made in Austria, in 1849,
amounted to 50,000 cwt.; and that in France, in 1850, the phosphorus
consumed in the manufacture of matches, amounted yearly to 590 cwt.;
and the consumption has rapidly increased since that time. In this
country, it is calculated that eight tons of phosphorus are yearly used
in making matches, the number of which is stated to be 40,000,000 a
day. Large quantities are also imported from Germany, where they are
manufactured so cheaply, that fifty boxes each containing 100 matches,
are sold for fourpence.

The latest improvement in chemical matches is the "Vesta," which
consists of small wax, or stearine tapers, with an igniting composition
at the end, consisting of chlorate of potass and phosphorus. These
Instantaneous Lights are made without sulphur, consequently the
disagreeable smell of the common Lucifer is avoided. The convenience
of smokers has also been consulted in the manufacture of Instantaneous
Lights. The fusees, now so frequently used for lighting cigars, are
composed of thin card-board cut half through, steeped in nitre and with
a small quantity of phosphorus; and the tearing of the paper across
produces sufficient heat to ignite the inflammable card.

Thousands of persons, principally children, are now employed in
the manufacture of chemical matches. The occupation, as at present
conducted, is very unhealthy, for the fumes of the phosphorus produce
a disease of a remarkable kind in the jaw-bone, which often proves
fatal. No cure has yet been found for this peculiar disease, occasioned
by the phosphorus in the state in which it is commonly used. A
preparation of that substance has, however, been made which may be used
without injury, and which possesses the advantage also of being less
dangerously inflammable; but as the red _amorphous phosphorus_, as it
is called, is rather more costly, the manufacturers of Lucifer matches
object to use it.




PAPER MAKING MACHINERY.


Cheap literature and the large development of newspapers are
principally attributable to the improvements in Paper Making, by the
aid of machinery.

In the former modes of making paper, the workman held in his hands a
square frame covered with wires, which he dipped into the prepared
cotton or linen pulp, which was kept in suspension by being agitated in
water, and taking up a quantity sufficient to cover the frame, he moved
the pulp about horizontally, to spread it evenly over the surface of
the wires. Another workman transferred the layer of pulp on to felt,
and in this manner one sheet was laid upon another, with felt between
each. They were next subjected to great pressure, for the purpose of
making the fibrous particles cohere sufficiently to form sheets of
paper. The felts were then removed, and the sheets were piled upon one
another and again pressed, after which they were dried, sized, and
finished.

Paper Making, by that process, was a slow operation. The thickness
and evenness of the sheets depended altogether on the judgment and
skill of the workman, and their size was necessarily limited by the
dimensions of the frame. By the improved methods, nearly all the work
is done by machinery. The soft fibrous pulp, which is to be converted
into paper, enters the machine at one end, and in the course of two
minutes it is delivered at the other end of the machine in a continuous
sheet, that may extend for miles. By supplemental contrivances the
paper is cut into sheets, piled together, and presented in a salable
form.

The world is indebted to a Frenchman, named Louis Robert, for the
invention of the first machine for making paper. He was a workman in
M. Didot's paper mill, at Essones, and for his contrivance of a method
for making continuous paper, he obtained from the French Government, in
1799, the sum of 8,000 francs and a patent for the manufacture of the
machines. The political agitation in France at that period prevented
much progress from being made with the invention, but after the Peace
of Amiens, in 1802, M. Didot, jun. came to this country, accompanied by
his brother-in-law, Mr. Gamble, for the purpose of making arrangements
to carry it into effect. They induced Messrs. H. and S. Fourdrinier to
engage with them in bringing the machinery to perfection, and patents
obtained in this country by Mr. Gamble were assigned to them in 1804.

The engineering establishment of Mr. Hall, at Dartford, in Kent, was
selected as best adapted for the purpose of making the machinery and
for carrying the plans into operation. Mr. Bryan Donkin, who was
engaged in the manufactory, principally assisted in bringing the
machinery to perfection. The difficulties attending the completion of
all the parts, to get them to work effectually, and the obstruction
encountered in introducing the machine-made paper, rendered the
enterprise a ruinous speculation to those who first engaged in it.
Messrs. Fourdrinier having expended £60,000 in perfecting the machine.

[Illustration]

The apparatus, of which a representation is given in the annexed
woodcut, was very complicated, but the essential parts may be readily
understood.

The rags from which the paper is made undergo a variety of processes
before they are properly reduced into a state of pulp. They are sorted,
dusted, boiled, and torn into pieces by passing through cutting
rollers; they are then bleached and again submitted to the grinding
action of rollers, which reduce them into a state of fine pulp,
resembling milk in appearance. The pulp thus prepared is placed in a
large vat, where it is kept constantly agitated, to prevent the more
solid parts from being deposited. From the vat the pulp is discharged
into a cistern, over the edge of which it flows in a continuous stream
upon an endless wire cloth, the meshes of which are so fine that there
are as many as 6,000 holes in a square inch.

The wire gauze, on to which the pulp is poured, is about 4 feet wide,
and 25 feet long, and it is kept constantly moving onwards, by rollers
at each end, over which it passes. The gauze is stretched out perfectly
level, and the pulp is prevented from flowing over the edges by straps
on each side, which limit the width of the paper. As the endless
wire cloth moves along, an agitating motion is given to it, by which
means the pulp is spread evenly over the surface; the water is also
drained off through the interstices of the gauze, and this part of the
process is expedited in the improved machines by producing a partial
vacuum underneath. Before the sheet of pulp has arrived at the farther
extremity of the wire cloth, it passes between two cylinders, the under
one of which is of metal, covered with felt, and the upper one of wood.
A slight pressure given to the pulp in passing between those cylinders
imparts sufficient tenacity to it to enable it to be transferred from
the wire gauze on to an endless web of felt, by means of a slice that
clears the pulp from the wire gauze, and deposits it on the felt. The
latter is kept moving at exactly the same speed as the wire gauze,
otherwise there would be either a rent or a fold on the sheet. The
paper, still in a very wet state, is carried between cast iron rollers,
and its fibres are forcibly pressed together, which operation squeezes
out the water, and so far gives tenacity to the pulp that it may be
handled without tearing. The sheet then passes on to other rollers, by
which it is further compressed, and its surface smoothened. The paper
is, however, still damp, and requires to be dried. This is done by
passing it over large metal cylinders, heated by steam. The process of
making the paper is then completed, and the continuous sheet may be
wound upon a reel to any length; but it is now usual to cut it up into
sheets as soon as it leaves the drying cylinders.

The wire cloth moves at the rate of from 25 to 40 feet per minute, and
such a machine would consequently make at least 10 yards of paper in
that time, which is equal to a mile in three hours. The width of the
paper is usually about 4½ feet, therefore each machine will make 10,450
square yards of paper in twelve hours; and there are upwards of three
hundred of such machines at work in this country. The value of the
paper thus produced is calculated to exceed two millions sterling.

Numerous improvements have been made in Fourdrinier's original machine,
but the principle of its construction remains essentially the same,
and it is by this means that most of the paper now used for writing
or printing is manufactured. A paper-making machine, on a different
principle, has, however, been invented by Mr. Dickinson, and has been
carried by him to great perfection. Instead of allowing the pulp to
fall on to a flat surface of wire gauze, a polished hollow brass
cylinder, perforated with holes and covered with wire cloth, revolves
in contact with the prepared pulp, and a partial vacuum being produced
within the cylinder, the pulp adheres to the gauze, and its fibres
cohere sufficiently, before the cylinder has completed a revolution, to
be turned off on to another cylinder covered with felt, on which it is
subjected to pressure by rollers, and is thence delivered to the drying
cylinders.

Mr. Dickinson afterwards obtained a patent, in 1855, for making a union
paper, consisting of a thin sheet of that made by his own machine, and
a similar sheet made by a Fourdrinier machine united together. For
this purpose the two sheets were brought together, as they passed from
the machines, whilst still wet and in an unfinished state, and were
pressed together between rollers, by which means they were completely
incorporated. The object of this contrivance was to combine, in a
single sheet, the different kinds of surface which paper made by those
two modes of manufacture present. It is also employed economically
for engravings, to give a fine surface to a thick sheet of coarser
material. The threads in postage envelopes and in bankers' cheques, are
introduced by this process of plating two surfaces together.

The greatly increased consumption of paper threatened to exhaust
the supply of the raw material, notwithstanding the large import
from abroad and the enormous supply derived from the waste of the
cotton mills, which, when mixed with rags, produces good paper. The
quantity of old rags, old junk, and other fibrous materials imported
for the purpose of making paper, in 1850, is stated in the Jury
Reports of the Great Exhibition to have amounted to 8,124 tons.
This large importation, added to the stock of rags supplied by the
country itself, was, however, inadequate to meet the consumption, and
search was anxiously made for other fibrous substances that could be
converted into paper;--peat, cocoa-nut fibre, grass, straw, and even
wood have been used for the purpose. Of those substances, straw has
been most successfully applied, and straw paper--excellent to write
upon, though not bright in colour--is now made at very low prices.
The straw is first cut up into short lengths, of about half an inch,
by a chaff-cutting machine, and after undergoing various processes of
trituration and bleaching, it is reduced into a pulp, sufficiently
adhesive to make a strong paper.

The plan of drying the paper as it leaves the rollers of the machine,
was introduced by Mr. Crompton in 1820, and that gentleman was also the
first to introduce a machine for cutting the paper into sheets as soon
as it is dried. The first invention of the kind was patented by Mr.
Crompton, in conjunction with Mr. Miller and Professor Cowper, in 1828.
The continuous web of paper was made to pass directly from the drying
apparatus to the cutting machine, by which it was first slit into bands
of the required width by means of a series of sharp discs of steel,
adjustable on two parallel axes. The bands of paper then passed on to
shears, placed transversely, that cut it into sheets of any required
length, which were laid upon one another, to be divided into quires.

Several other cutting machines have since been invented, the simplest
of which is the one patented by Mr. Dickinson, which is represented in
the woodcut.

[Illustration]

The paper may be taken directly from the drying cylinders or from a
reel, as shown in the diagram at _a_. The sheet passes over a large
drum and through several guide rollers, till it is carried across
the table _a h_, where it is cut lengthwise by knives, as it passes
along. A series of chisel-edged cutters are placed at regulated
distances beneath the table; and whilst the paper is stretched over
it, several circular knives, _f f_, fixed into a swing frame, _g g_,
at corresponding distances with the knives beneath, are swung across
the sheet, and cut it in the manner of a pair of shears. Other kinds of
cutting machines are contrived, by which sheets of writing paper, when
collected in quires, are squeezed tightly together, and their edges are
smoothly and evenly cut.

We must not conclude this notice of Paper Making Machinery without
alluding to the ingenious self-acting mechanisms for making envelopes.
In the Great Exhibition of 1851 there were three different machines
exhibited in action, each one producing, with great rapidity, those
neat coverings for letters, for which the penny postage system has
created so great a demand. The paper, cut into the desired form by a
separate machine, was piled up on one side of the envelope folder.
It was taken, sheet by sheet, and stretched on a small table, on the
middle of which there was a trap door, held up by a spring to a level
with the rest of the table. A plunger, of the same size as the envelope
to be made, pressed the trap down into a recess, and raised the four
corners of the paper, the edges of which were then gummed, and small
mechanical fingers folded them down. The completed envelope was then
thrown out into a basket, or it slided out of the machine on to those
before made.

Each of those machines, with a boy as an attendant, will fold
2,700 envelopes in an hour, which is nearly the same number that
an experienced workman can fold in a day with a folding stick.
Notwithstanding the supplanting of manual labour to so great an extent
by these ingenious mechanisms, the effect of increased facility of
manufacture has been to give increased employment, and many more
persons are now engaged in making envelopes than were so employed
before the invention of the machines.




PRINTING MACHINES.


The associated inventions of paper making and printing have progressed
hand in hand together; the increased facility with which paper can
be made by machinery having been equalled, if not surpassed, by the
rapidity with which it can be printed.

The old wooden printing press, that was in general use at the beginning
of the present century, is now an object of curiosity, and a few
specimens of it are to be seen, even in country printing offices.

The principal working part of the wooden press consisted of a block
of wood, having a perfectly flat and smooth surface, half the size of
an ordinary sheet of printing paper, which was brought down upon the
types by means of a screw that was turned by a long lever. The types,
placed upon a flat stone embedded in a movable table, were inked with
large soft balls covered with pelts. The damped paper was put into a
frame, at the back of which blankets were placed, and was laid lightly
on the inked types. The movable table was then pushed under the block
of wood, called the "platten," the long lever was pulled with great
strength, and the platten being thus brought forcibly upon the blankets
and paper, one-half of the sheet was printed. The lever, on being
released, sprang back to its former position, and the table with the
types upon it was pushed farther under the platten, which was again
pulled down to print the other half of the sheet. The table was then
pulled back, and the sheet of paper, printed on one side, was removed.
These operations occupied considerable time, and the regular work of
two men, with a wooden press, was to print 250 sheets an hour on one
side.

This original contrivance for printing was supplanted by the Stanhope
press, one of the most admirable arrangements for the advantageous
application of the lever that is to be found in the whole range of
mechanical contrivances.

The improved printing press, invented by Lord Stanhope, the first of
which was completed in 1800, is made altogether of iron. The platten is
of the full size of the sheet of paper to be printed, and the work is
done at a single pull. The requisite power is obtained by a combination
of levers, so adjusted that the platten is brought down rapidly in the
first instance, before any pressure is required, and when it comes
to bear upon the types, the levers act with the greatest possible
mechanical advantage, so that the handle moves through the space of a
foot, whilst the platten descends only the twentieth part of an inch.
By this means a large sheet of paper can be printed off by a single
pull, and with more impression and greater sharpness than by two pulls
with a wooden press.

Great as was this improvement in the printing press, its action was
still very slow, compared with the rapidity of printing we are now
accustomed to, it being considered quick work, with a small Stanhope
press, to print 500 sheets an hour. The author remembers to have seen
the _Globe_ newspaper printed by an old wooden press in 1820; and,
about the same time, the London _Courier_, by a Stanhope press. In
order to supply the large demand for the latter paper, it was then
customary to print off three pages early in the day, and to set up
the types for the fourth page, containing the latest news, three or
four times, and to print it at as many separate presses. The pressmen
could thus, by great exertion, perfect the printing, when three presses
were used, at the rate of 1,500 an hour. The _Times_ newspaper, which
greatly exceeds the size of the _Courier_, is now printed by a machine
at the rate of 13,000 an hour.

The invention of printing machines was preceded by the manufacture of
inking rollers, to supersede the pelt balls for distributing the ink
over the types. Earl Stanhope had endeavoured in vain to construct
inking rollers, for which purpose he tried skins and pelts of various
kinds, but the seam proved an obstacle that he could not overcome. In
1808, a "new elastic composition ball for printing," which consisted
principally of treacle and glue, to serve as a substitute for pelts,
was invented by Mr. Edward Dyas, a man of great original genius,
the parish clerk of Madeley, in Shropshire. These balls were first
introduced into the extensive printing office of the late Mr. Edward
Houlston, of Wellington, where they were for some time exclusively
used, and that printing-office consequently became celebrated for the
excellence of its work. A similar composition was some years afterwards
cast in the form of rollers, upon a hollow core of wood, by the late
Mr. Harrild; and these rollers have proved a far more cleanly and more
expeditious mode of inking the types than the balls. These inking
rollers supplied an essential want in the working of Printing Machines.

The invention of Printing Machines underwent many changes before it
was brought to a practical form. Such a machine was first projected
in 1790, by Mr. Nicholson, who proposed to place the types and paper
upon cylinders, and to distribute and apply the ink also by cylinders.
Another plan, more closely approaching that of the printing machines
afterwards perfected by Mr. Napier and others, was to place the types
upon a table and the paper upon an impressing cylinder, and to move
the table backwards and forwards under it. In 1813, Messrs. Donkin and
Bacon proposed placing the types upon a prism, which was to revolve
against an irregularly shaped cylinder, on which the paper was to be
placed. Nothing, however, could be effectually done in producing a
proper working printing machine until the invention of inking rollers.

In 1814, Messrs. Bauer and Kœnig succeeded in constructing a machine,
which was erected at the _Times_ office, that produced 1,800
impressions an hour; and it continued in use till 1827. This rapidity
of action, compared with that of the most improved printing press,
produced a revolution in the art of printing; attention was then
directed almost exclusively to the further improvement of the machines,
and the platten press was neglected.

In the form of printing machines generally used, the types are laid
upon an iron table that is moved to and fro by the turning of a wheel
connected with a steam engine. The paper is placed upon cylinders
covered with flannel, and the impression of the types is produced by
the cylinders being fixed so closely to them that, as the table passes
backwards and forwards, there is great pressure. The types are inked by
a series of rollers, by which the ink is distributed and evenly laid on
the face of the types without any manual labour.

The mechanical power gained by an arrangement of this kind arises from
the pressure being exerted on a small surface at a time; consequently
the power required for producing the impression of the types is not
nearly so great as when the whole surface of the types makes the
impression at the same instant. The force actually pressing on the
types, from contact with the cylinders, is very much less than that
brought to bear on them by the platten of the Stanhope press; but as
it acts on a smaller surface at a time, the amount of pressure on
each part, successively, greatly exceeds that received by any similar
portion when it is impressed all at once. The difference of the action
of the platten and of the cylinder may be compared to the different
effects produced by a knife when pressed with its edge and with its
flat side against a yielding surface; the pressure on the flat surface
may not be sufficient to leave any impression, whilst a much smaller
pressure on the edge will produce an indentation.

[Illustration]

The accompanying woodcut is a representation of one of Messrs.
Applegath and Cowper's machines for printing both sides of the paper at
the same time.

It consists of a cast-iron frame, about 14 feet long and 4 feet wide,
on which the iron table, with the types upon it, slides backward and
forward under two large cast-iron cylinders, covered with blankets,
whereon the paper is laid. The pages of type to be printed on one side
of the paper, and those pages that are to be printed on the back, are
wedged into iron frames, called "chases," and these chases are fixed
on the table at such a distance from each other, that they will pass
under the two cylinders in the same relative positions. The sheets of
paper are held on to the cylinders at their edges by means of tapes,
and are so laid on by the workmen, that the type may be impressed on
them with an equal margin all round. At each end of the machine is
a supply of ink, which is taken from long iron rollers, about three
inches in diameter, each of which turns in contact with a flat iron
bar, that only allows a small quantity of ink to pass. A composition
inking roller is made to vibrate between the inking table, where on the
ink is thinly and evenly spread, and the iron feeding roller, and thus
delivers the requisite quantity of ink on to the table. Several other
composition rollers are placed across the inking table, with their
axes resting in notched bearings, so that as the inking table moves
forward and backward, those rollers distribute the ink evenly over it.
There are four other rollers (none of which are shown in the diagram),
which take the ink from the table; and as the types pass from under
the cylinders, after printing a sheet, and return to them, they pass
twice under the inking rollers. Each sheet of paper is laid by a boy on
a web of tapes, by which it is carried round one paper cylinder, and
then over and under two wooden drums to the other paper cylinder. The
sheet of paper, in the course of its progress, is turned over, so as to
receive the second impression on the other side; and as the tapes that
carry it along leave the second cylinder, they divide, and the printed
sheet falls into the hands of a boy.

In the printing machine which was shown at work in the Great
Exhibition, invented by Mr. Applegath and made by Mr. Middleton, for
printing the _Times_, the arrangements differ materially from those of
the horizontal machines already described. The types, instead of being
placed on a table, and moved to and fro under the impressing cylinders,
are fixed to a large vertical cylinder, upwards of 16 feet in diameter,
and there are eight impressing cylinders ranged vertically round it,
with their axes fixed. By this arrangement there is no loss of time in
withdrawing the types from under the cylinder to be again inked, but
they move round from one fixed cylinder to another, receiving their
ink between each, and thus producing eight impressions in succession
during one complete revolution. At the _Times_ printing office there
are now three machines of that construction, two of which, with eight
cylinders, print ten thousand an hour, and the other one, which has
nine impressing cylinders, thirteen thousand.

The operations for printing that newspaper exhibit marvellous efforts
of human ingenuity and skill, brought to bear in producing with the
requisite rapidity a sufficient number of impressions to supply its
enormous circulation. After the types have been composed and corrected,
and ranged into columns and screwed up into their chases by upwards of
one hundred hands, each page of type is attached to the large vertical
cylinder--a curved form having been given to the type to adapt it to
the circular surface. Nine men, standing each one beside a heap of
damped paper, feed the largest machine by separating the sheets singly
from the heap, and present them successively to the action of small
rollers, that give each sheet a forward impulse, which brings it within
the grasp of a series of endless tapes. These tapes catch hold of the
sheets of paper, and carry them down to the level of the types. They
are then shot along horizontally to the pressing rollers, covered with
blankets, round which they are carried and pressed against the types;
after which the endless tapes carry them away, and deliver them printed
to a man below, who spreads them one over the other. A large reservoir
of ink at the top of the machine supplies the inking tables, from which
it is spread evenly over the inking rollers, and, at each revolution
of the type cylinder, nine sheets are printed on one side. They are
then taken to a second machine to be printed on the back, or, as it
is called, "perfected." The accompanying engraving shows the general
arrangement of the machines.

Few mechanical contrivances present so striking an illustration of
the application of human ingenuity to the production of important
results, and to the saving of labour, as these printing machines. To
see the sheets of paper travelling along the tapes--to see them shoot
downwards, carried sideways in one direction and back again, and
delivered with half a million of words impressed upon them in less than
three seconds, seems like the work of magic. To copy that number of
words, thus printed in three seconds, would occupy a rapid penman forty
days, working ten hours a day.

[Illustration]

Great as are the printing powers of these machines of Mr. Applegath's,
they have been surpassed more recently by one placed close beside them,
invented by Mr. Hoe, of New York. In that machine the type cylinder
is placed horizontally, by which means the paper is supplied directly
to it without altering its direction. As many as twenty thousand
impressions in an hour have been produced by the American machine, but
it is not yet sufficiently perfected to be brought into regular use.

In another part of the _Times_ establishment there is an ingenious
machine for wetting the paper, by which contrivance much labour and
time are saved. The paper, heaped in a pile at one end of a table, is
presented in quires at a time to the action of a roller, which drags
it on to a moving endless blanket, that is kept wet by a stream of
water, and the upper surface is wetted by a long brush, placed over
the blanket. The wetted paper is heaped upon a truck, which gradually
descends, to keep the upper sheets on a level with the table, till
the paper is piled up a yard in thickness. The truck is then raised,
by hydraulic pressure, to the level of the floor, and is wheeled away
and another one is loaded. Between nine and ten tons of paper are thus
wetted daily; and the sheets of the _Times_ printed during a year, if
spread out and piled one upon another, would form a column as high
as Mont Blanc. The quantity of ink daily consumed in the printing
is upwards of two hundredweight. The machine is worked by two steam
engines, each of 16-horse power; and the noise of the numerous wheels
and rapidly revolving cylinders is almost deafening.

The great rapidity and the comparative cheapness of printing by
machines, together with the greater facility of making paper by
machinery, have been the means of creating a demand for books which
it would be impossible to supply, unless those means were at command.
Thousands and hundreds of thousands of copies of publications, that
spread knowledge among the people of the highest interest to the
welfare of man, and replete with useful information of every kind,
are now sold at prices which would be impossible, were it not for the
improvements that have been made in the manufacture of paper, and in
the means of printing.

Nor should we omit to notice, as one of the causes that have
contributed to the production of cheap literature, the art of
stereotyping, which has been perfected during the present century. Earl
Stanhope, the inventor of the admirable press that bears his name, was
prominent in bringing that art to perfection.

Numerous attempts had been made in the last century to produce casts
from pages of type. So early, indeed, as 1700, some almanacks and
pamphlets were printed in Paris from castings; and an edition of
Sallust was printed in Edinburgh in 1739, from stereotype plates
produced by Mr. Ged, a goldsmith. The process, however, was not
encouraged, and on his death it was not further proceeded with. The
most important advance in the art was made by M. Hoffman, of Alsace,
who, in 1784, succeeded in obtaining stereotype plates by casting
them in moulds of clay mixed with gelatine in which the pages of
type were impressed, with which he printed a work in three volumes;
but the castings were imperfect, and the plan was soon afterwards
abandoned. Among the many plans tried to obtain perfect casts of the
types when set up, was one contrived by M. Carez, a printer of Toul,
who, in 1791, endeavoured to obtain casts in lead from a page of type,
by allowing it to drop on the fused metal when it was in a state of
setting. The matrices thus obtained were in like manner impressed on a
fusible metal, which melted at a lower temperature than the lead. Good
casts were often thus procured, but the uncertainty of the process,
arising from the frequent fusion of the lead matrices, caused it to
be discontinued. Other plans were tried in France with more or less
success, but nothing was done practically until Lord Stanhope directed
his attention to the subject in 1800, and resorted to the original
method of obtaining matrices, by impressing the pages of type in a cold
plastic substance. He employed plaster of Paris for his mould; and when
they were thoroughly dried, they were plunged in fused type-metal; and
in this manner a perfect cast in metal of the original page of movable
type was produced. The process has been still further perfected, and
casts from movable types, and from wood engravings, are now made with
great facility, and the impressions from them are quite equal to the
originals.

When it is intended to stereotype a work, the movable types used in
composing it are new, and the "spaces" that separate the words from
each other are longer than is customary when the type is to be printed
from. These elongated spaces reach nearly to the face of the letters,
so that the plaster may not sink between them. By this means the mould
is easily removed from the face of the page of type. The metal casting
of each page is very thin, and when required to be used, it is screwed
on to blocks of wood to the same height as ordinary types.

Several attempts have been made to apply other substances than plaster
of Paris and type-metal for stereotyping. At the Great Exhibition there
were specimens of gutta percha stereotypes, that produced excellent
impressions, and there were also fine stereotype castings of type in
iron, from which a copy of the Bible had been printed. Papier maché has
been found to be a material peculiarly applicable for the purpose, and
it is now superseding the use of plaster of Paris for taking casts of
the types.

By the application of the art of stereotyping, casts in metal of
valuable works can be kept ready at any time, to be printed from when
more copies are required; and the expense is saved of keeping on hand
large stocks of printed paper, or of having a work recomposed when a
further edition is wanted.

The inventions of Printing Machines and stereotyping were strongly
opposed at first by pressmen and compositors, as calculated to diminish
the demand for their labour. In "Johnson's Typographia," published
in 1824, the "new-fangled articles" are mentioned in a spirit of
great bitterness; and the writer thus poured forth his lamentations
at the prospective ruin of the members of his profession:--"We are
much surprised at the apathy and supineness shown by the body of
master printers with respect to the subject under discussion; they
most assuredly had good and sufficient grounds for an application to
Parliament for a tax, that should bring the work so executed upon an
equality with that done by manual labour."--"We feel satisfied that the
above would not have met with encouragement from a British public, had
they been aware of the evils attendant on it; they have not only to pay
a full price for the work, but also extra poor's rates, in consequence
of the men being thus out of employ; likewise they are countenancing
the breaking up and destruction of all the energy and talent of that
art which was England's proudest boast, and her shield against all the
threats of her foreign foes."

These predictions of ruin have been completely falsified. It has been
with the Printing Machines as with most other improved machinery for
the saving of labour: on their first introduction some hands, no doubt,
were thrown out of employ, but the advantages derived from the saving
of labour very soon reacted favourably in creating a greater demand for
labour than before. The number of cheap periodicals, and the extensive
issues of cheap literature in every form, require a much larger number
of workmen to supply the demand, even with the aid of machinery, than
was needed in the best days of the manual printing press; and at no
time were so many compositors and pressmen employed as at present.

In the Reports of the Juries of the Great Exhibition, some interesting
statistics are given, showing the influence of the invention of
Printing Machines in extending the demand for books and periodicals.
"The machine," it is observed, "created a demand, and called into
existence books which, but for it, would scarcely have been thought
of. As the machine-work from type and woodcuts was far better than
the ordinary printing of the day, booksellers were induced to print
extensive editions, because they saw the machine could accomplish all
they required. One of the first booksellers who availed himself of this
power was Mr. Charles Knight, who projected the 'Penny Magazine,' on
a hint from Mr. M. D. Hill, Queen's Counsel. Each number, published
weekly, consisted of eight pages of letterpress, illustrated with
good wood engravings. The public was astonished at the cheapness and
good quality of the work, but it was its immense sale which rendered
it profitable; for some years it amounted to 180,000 copies weekly.
Mr. Knight, whose services in the cause of educational literature
entitle him to the highest praise, expended £5,000 a year in woodcuts
for this work. The Cowper machine has been the cause of the many
pictorial illustrations which characterize so large a portion of
modern publications. The 'Saturday Magazine,' 'Chambers' Journal,'
the 'Magasin Pittoresque,' in France, and numerous others, owe their
existence to this printing machine. The principle of _cheap editions
and large sales_ soon extended to established works of a higher value.
A remarkable instance of this was the edition of Sir Walter Scott's
Works, with notes, edited by himself; instead of the old price 10s.
6d., they were sold at 5s. a volume,[15] and the demand created by
this reduction in price was so great, that, though the printer had a
strong prejudice against machines, he was compelled to have them, the
presses of his large establishment proving totally unable to perform
the work, which amounted to upwards of 1,000 volumes per day for about
two years. The Universities of Cambridge and Oxford have adopted Mr.
Cowper's machines for printing vast numbers of Bibles, prayer-books,
&c., &c. A Bible which formerly cost 3s. may now be had for 1s. Mr.
Cowper recommended the Religious Tract Society to put aside their
coarse woodcuts, to have superior wood engravings, and to print with
his machine. The Society adopted those suggestions, and the result is,
that by sending forth well-printed books, it could now support itself
by their sale, without any aid from subscriptions."

As an illustration of the facilities afforded by the invention of
Printing Machines in producing cheap editions of the writings of
popular authors, the following curious facts relating to the Works of
Sir Walter Scott, in addition to those furnished in the Reports of the
Juries, may be found interesting.

In 1842, a general issue of these Works, in weekly sheets or numbers,
at twopence each, was commenced by the late Mr. Robert Cadell, of
Edinburgh, and completed in 1847. Of this edition, up to the present
period (1858), the astonishing number of TWELVE MILLIONS OF SHEETS
have been issued, the weight of which amounts to upwards of 335
tons! Another edition was published simultaneously by Mr. Cadell in
monthly volumes at 4s., each containing about 360 pages; this series
has reached a sale of more than 500,000 volumes. A third cheap issue,
at eighteenpence a novel, is now being published by the present
proprietors, Messrs. Adam and Charles Black, of Edinburgh. Nearly
300,000 volumes have already been printed of this edition.

It may be mentioned here, although hardly coming within the scope
of the present article, but as affording a striking example of what
literature has contributed to the revenue of the country in the person
of a single author, that upwards of 3,500 tons' weight of paper[16]
have been consumed in producing the various editions of Sir Walter
Scott's Writings and Life; and the duty paid to Government on the
paper, even at the present reduced rate, amounts to no less a sum than
£51,450!

Since the Juries made their Reports, the development of cheap
literature has been greatly extended. Newspapers, some of which contain
eight full-sized pages, of six columns each, printed in small type, are
sold for the marvellously low price of a penny, and are stated to issue
as many as 50,000 copies daily; and some of the newspapers and other
periodicals, printed on good paper, are issued for a halfpenny. Among
the works of a standard character, published at prices which nothing
but a very extensive scale could make remunerative, may be mentioned
the popular series which includes "The Reason Why," and "Enquire Within
upon Everything." Of the eight volumes already issued, each containing
about 350 closely printed pages for half-a-crown, nearly 170,000 copies
have been sold within a period of less than three years.




LITHOGRAPHY.


The art of printing from stone was invented at the end of the last
century by M. Aloys Senefelder, of Munich; but it was not brought to
such a state of perfection as to be practically useful until many years
afterwards.

The principle on which Lithography depends is the different chemical
affinities of water for oily and for earthy substances, which cause
it to run off from the one and adhere to the other. The drawing or
writing is made in oily ink upon a smooth calcareous stone that will
absorb water, so that, when the stone is moistened, the water adheres
to it and leaves the lines of the drawing traced upon it dry. An inking
roller, charged with an oily ink, is then passed over the stone and
inks the drawing, but leaves all the other parts of the stone quite
clean. A damped paper is next laid on, and when subjected to great
pressure, an exact copy of the drawing or writing is produced.

This simple and ingenious process has been carried to such perfection,
that the most beautiful artistic effects can be produced by it far
more economically than by any other style of engraving; and further
improvements in the art are being continually made. It is satisfactory,
therefore, to be able to trace its history from its very beginnings, of
which an interesting account has been published by the inventor himself.

M. Senefelder's father was an actor at Munich, and in his youth he
followed the same profession. He turned his attention afterwards to
music; and it was in his attempts to devise some means of printing
his compositions economically that he chanced to discover the art of
Lithography.

He had previously made himself acquainted with the methods of
copper-plate printing, and he commenced his operations by etching the
notes of music on copper-plates, covered with varnish in the ordinary
way. He found, however, that it would require much practice to enable
him to do this properly, and not being able to buy copper-plates for
his rude essays, he thought of practising upon stones. Fortunately for
the success of his efforts, the quarries at Solenhofen, near Munich,
supplied him with slabs of stone admirably adapted for the purpose; and
it is a remarkable coincidence, that the material which Senefelder used
for his experiments is the best for the purpose of Lithography that
has hitherto been discovered. His chief object in making use of these
slabs of stone was to practise himself in the manipulation of writing
the notes, and of biting them in with _aqua-fortis_ (nitric acid),
as he supposed the slabs would be too brittle to bear the action of
the press. He did not try, therefore, to have these etchings on stone
proved by the press, but he contented himself with holding them up to a
mirror to observe the progress he was making in writing backwards.

Having at length been supplied with much thicker slabs of stone, to
bear the requisite pressure, he endeavoured to grind and polish them
sufficiently for the purpose of being printed from, in the same manner
as copper-plates. He succeeded to some extent in doing so, by means
of diluted nitric acid; and he contrived to obtain about fifty good
impressions from the stone.

In all these attempts at Lithography, the lines were etched into the
stone by the action of nitric acid, and the only advantages professed
to be gained by the process were the questionable ones of comparative
cheapness of material, and greater facility of working. M. Senefelder
admits that there was nothing new in engraving upon stone; all that
he claims in that part of the invention is, the manner of polishing
the surface, and the composition of the ink adapted for printing
from it. The most important step in the progress of the invention of
Lithography, as at present practised, was made by accident, which he
thus describes:--

"I was preparing a slab of stone for engraving, when my mother asked
me to write a memorandum of things she was about to send to be washed.
The washerwoman was waiting impatiently whilst we searched in vain for
a piece of paper, and the common writing ink was dried up. Having no
other writing materials, I wrote the washing bill on the stone I was
about to prepare for engraving, using for the purpose my ink made of
wax, soap, and lamp-black, intending to copy it afterwards on paper.
Whilst looking at the letters I had written, the idea all at once
occurred to me how it would do to cover the stone, with the writing
upon it, with aqua-fortis, so as to leave them in relief, and then to
print from them in the same manner as woodcuts, with a common letter
press. The attempts I had hitherto made to engrave upon stone had
taught me that the relief of the letters thus obtained would not be
much. Nevertheless, I made the attempt. I mixed one part of aqua-fortis
with five parts of water, and poured it on the stone to the height of
two inches, having previously walled it round with wax in the usual
manner. The diluted aqua-fortis was permitted to rest on the stone five
minutes. I then examined the effect, and I found that the letters were
raised above the stone about the thickness of a card. Most of the lines
were uninjured, and retained their original size and thickness. This
gave me the assurance that writing, sufficiently traced, especially
if the letters were in printed characters, would have still greater
relief."[17]

Though M. Senefelder had advanced thus far, he had not yet made
application of the chemical properties of ink and water, which
constitute the distinguishing characteristics of Lithography. That was
reserved for a further discovery, also brought about by accident. The
difficulty he experienced in writing words on the stone in the reverse
way, induced him to adopt the plan of writing the letters on paper with
a soft black-lead pencil, and then transferring them on to the stone by
pressure. He subsequently used lithographic ink for the purpose; and in
the course of his experiments he observed, that when a paper written on
with lithographic ink, and well dried, was dipped into water on which
some oil was floating, the oil adhered to the writing, and left the
rest of the paper clean, and that this effect was most striking when
the water contained some gum in solution. This discovery induced him
to try the effect on printed paper; and, taking a printed page from
an old book, he moistened it with gum-water, and afterwards sponged
the whole surface with oil colour. The colour adhered to the letters,
and left the paper clean, and after further experiments he succeeded
in printing as many as fifty copies from a page of printed paper; the
letters, of course, being reversed. The idea then suggested itself of
transferring, on to stone, letters written with lithographic ink upon
paper. The plan succeeded, and the principle of the art of Lithography
was thus applied to practice. M. Senefelder, in his subsequent
improvements, gave a slight relief to the letters by the original plan
of using diluted aqua-fortis, by which means the impressions obtained
were blacker. He also contrived the means of printing in colours from
stone, by reversing the process of ordinary lithographic printing. To
produce coloured prints, he left uncovered all the parts that were to
receive the colour, and the other parts of the stone were covered with
an oleaginous fluid, that quickly dried. On applying any water-colour
to the stone, it adhered to the uncovered surface, and not to the
covered parts, and that colour was transferred to paper by pressure. In
this manner, by using several stones properly prepared, the different
colours required were printed, and the effect of a coloured drawing was
produced. Thus we perceive, that almost at the first invention of the
art of Lithography, the ingenious inventor showed the way of applying
it to the production of coloured prints, a process which has lately
been carried to great perfection.

Senefelder lived to see his invention extensively adopted, and to reap
benefit from his ingenuity. He died at Munich, in 1834, after having
been many years the director of the Government lithographic office;
and, in the latter years of his life he received a handsome pension
from the King of Bavaria.

There is little to be added to the description of the process of
Lithography, beyond that given by the original inventor in 1819, the
principal advances that have been made in the art having consisted
in improved methods of manipulating. The ink now generally employed
for drawing on the stone consists of equal parts of tallow, wax,
shell-lack, and soap, mixed with about one-twentieth part of
lamp-black; but the composition is varied, according to the kind
of design to be executed. For writing or drawing upon paper, to be
transferred to the stone, more wax is added to the ink, to give it
greater tenacity.

The drawing upon paper, to be transferred to stone, is not attended
with any difficulty, and may be done by ordinary artists. The ink
is applied with a pen, or camel's hair pencil, and when the effect
of chalk drawings is required to be imitated, the ink is shaded by
means of stumps, similar to those used in chalk drawings on paper.
Some artists prefer to work directly on the stone with a camel's hair
pencil, or with a composition called lithographic chalk.

To transfer the drawing from paper on to the stone, the paper is first
sponged with diluted nitric acid, which decomposes the size, and
renders it bibulous. After being placed for an instant between blotting
paper, to remove superfluous moisture, it is laid with the drawing
downwards on the stone, which is slightly warmed. The stone is then
passed through the press, and the drawing adheres firmly to it. To
remove the paper, it is wetted at the back with water, and, when quite
soft, it is rubbed with the hand. In this manner every particle of the
fibrous pulp is cleared away, and the drawing or writing in ink remains
as if it had been drawn directly on the stone. To prepare the stone for
taking the ink, gum water is poured upon it, and it is rubbed over with
a rag containing printer's ink, which serves to blacken the writing and
prepares the lines for afterwards receiving the ink.

The lithograph thus prepared is given to the printer, who first etches
it, in the manner originally practised by M. Senefelder. The nitric
acid employed for the purpose is diluted with about thirty parts of
water, and it is poured over the stone whilst it is inclined on one
side. This process is repeated several times, the object of it being
not so much to give relief to the lines, as to roughen the surface of
the stone, and thus facilitate its absorption of water. The nitric
acid also removes the alkali from the drawing ink. In printing, gum is
added to the water with which the stone is moistened, as an additional
preventive of the ink adhering to those parts not drawn upon. The
printing ink is applied with large rollers, and the damped paper having
been placed carefully upon the stone, with blankets at the back, it is
passed through the press.

The lithographic press somewhat resembles in form an iron printing
press, but differs from it greatly in its mode of action. Instead of
the large flat plate that in a printing press is pulled down upon the
whole surface of the types, a long, narrow arm, called a scraper, is
brought to bear upon the stone, and the table whereon the stone is
laid is pushed forcibly under it, by which means a great pressure is
exerted on a smaller surface at successive times, instead of being
brought to bear all at once. In the principle of its action, indeed, a
lithographic press is like a printing machine, and steam lithographic
presses have been invented to work in a similar manner, though the
practical results have not generally been very successful.

Among the many applications of lithography, the transfer of
copper-plate engravings is one of the most useful. An impression of
the plate is taken on paper that is coated with a compound of flour,
plaster of Paris, and glue, and from the paper it is transferred to
stone. By this plan the original plate remains untouched, and the
printing from the stone is much cheaper than from the copper. Tinted
lithography and chromo-lithography, by which the beautiful effects
of coloured drawings are produced in the manner indicated by M.
Senefelder, have recently been applied very successfully.




AERATED WATERS.


The invention of soda-water, in the state in which it is now known,
as an effervescing beverage impregnated with three or four times its
volume of carbonic acid gas, is of very modern date. There are, indeed,
to be found in most of the old works on chemistry descriptions of
Nooth's apparatus for impregnating liquids with carbonic acid; but
all that was attempted to be done by that apparatus was to produce an
impregnation of the water with little more than the quantity of gas it
will naturally absorb under the pressure of the atmosphere. It was not
until about the year 1815 that mechanical pressure was applied to force
a larger quantity of gas into combination with water, to imitate the
briskly effervescing medicinal waters of Germany.

Mr. Schweppe and Mr. Paul were the first who introduced the manufacture
of artificial effervescing waters into England, and soda-water was then
considered, as tea was on its first introduction, entirely medicinal.
Indeed, the quantity of soda which was at that time usually dissolved
in the water gave it a disagreeable taste; but when the manufacturers
diminished the quantity of alkali, and increased the volume of gas
forced into the water, they produced a pleasant beverage, which soon
became in request for its refreshing, wholesome qualities.

The apparatus for the manufacture of soda-water, as it is usually
made on a large scale, consists of a strong vessel, furnished with a
safety valve, in which the water is impregnated with gas. This vessel,
containing about nine gallons, is made of thick wood, well seasoned and
nicely fitted, and bound round with strong iron hoops, the heads of the
cask being well secured by means of iron bolts and screw nuts. It is
requisite that the receiver should be capable of bearing a pressure of
at least six atmospheres, which is equal to 90 lbs. to the square inch.

The carbonic acid gas is generated from chalk or whiting and diluted
sulphuric acid. The materials are mixed together in a small closed
wooden or leaden vessel, provided with an agitator, that can be
worked by a handle fixed to a projecting axis at the top. The gas, as
generated, enters by a bent tube into a gas-holder, the opening of the
tube being under water. By this means the gas is freed from the fumes
of sulphuric acid vapour, and from the fine particles of chalk that
become mingled with it during its sudden liberation. The gas sometimes
undergoes a further purification, by passing through a gas washer,
before it is forced into the water.

A small force-pump, worked by a crank, with the assistance of a
fly-wheel, draws the carbonic acid from the gas-holder, and forces it
into the water. The combination of the gas and water is facilitated by
an agitator, the axle of which projects through a stuffing box, and it
is worked either by hand, or is turned by means of a small cog-wheel,
that works into the teeth of a larger one fixed to the crank axle, so
as to produce rapid rotation.

It is found requisite, in the first place, to expel the atmospheric air
in the receiver; for which purpose the safety valve is left open for a
short time after the gas is being forced in, otherwise it would retard
the impregnation of the water by the gas. When the gas and water are
well incorporated, the liquid will contain as many volumes of gas as
there are atmospheres of pressure in the air-space above it in a state
ready to effervesce, and one other volume, with water absorbs under
the pressure of the atmosphere. Thus, when there are three atmospheres
of gas under pressure, each bottle of soda-water contains four bottles
full of gas, which are absorbed without perceptibly increasing its
bulk. The perfect impregnation of the water with gas, however,
requires time. The water will, indeed, become brisk almost as soon as
two or three atmospheres of gas have been forced in, but it will not
acquire the flavour of good soda-water until the gas and water have
been allowed at least half an hour to digest; and it is improved by
remaining in contact for several hours.

The temperature has considerable influence in the process of
impregnation, for in hot weather the gas will not combine so readily,
nor will the water absorb an equal volume of gas. In summer time,
therefore, soda-water should be made before the heat of the day, and
ice should be added to the water.

When the receiver is fully charged, and the operation of bottling
begins, every bottle-full that is drawn off diminishes the pressure on
the water that remains; and if no means were taken to add more gas, the
soda-water would gradually become weaker and weaker as each bottle was
drawn off. It is usual, in the best arranged apparatus, to have two
tubes connected with the force-pump, one of which feeds it with water,
the other with gas, by which contrivance water and gas, in their proper
proportions, are continually forced into the receiver, which may thus
be always kept nearly full.

The process of bottling requires great manual dexterity. The neck of
the bottle is pressed by a lever against a collar of leather fixed to
a flange on the tap, so that, when the soda-water rushes in, no air
nor gas can escape. The pressure inside the bottle therefore quickly
becomes equal to that of the receiver, and the water ceases to flow
through the tap, until some of the air is allowed to escape. When the
bottle is nearly full, the operator quickly withdraws it with one hand,
and having a cork ready in the other, he puts it in before the water
can rush out. The cork is then forced in further by pressure, and
fastened down by wires or strings.

A bottling apparatus has been invented for facilitating the process;
but a man accustomed to bottle by hand can do it more quickly, and with
as little waste of gas and water as with a machine. Much depends,
however, upon the state of the soda-water in the receiver; for if the
gas be well digested, and the temperature low, it rushes into the
bottle with much less force, though the water may contain a greater
quantity of gas, than when it is newly made, and apparently more brisk.
The bottles very frequently burst during the operation with great
violence, and unless they are enclosed in a guard, the men are liable
to be severely injured. Glass bottles have now generally supplanted
those made of earthenware, which were formerly used; and though the
glass bottles are much stronger than the earthenware ones, the bursting
of them, when it does occur, is far more dangerous.

The process of forcing gas into the water by mechanical pressure,
in the manner described, requires great labour, for the pump has to
be worked against a pressure exceeding fifty pounds on the square
inch. With a view to remove that inconvenience, and to avoid the use
of costly machinery, so that private individuals might manufacture
soda-water, the author contrived a modification of Nooth's apparatus,
for which he obtained a patent in 1831. By that means, the gas is
generated in a closed vessel, and forces itself into the water by
its own elasticity. Any amount of pressure can thus be obtained by
chemical action alone. The accompanying woodcut represents a section
of the apparatus in its improved form. The vessel, A, is made of very
strong stone ware, inside which is the gas generator _b_. A few inches
from the bottom of the generator is the partition, _a_, perforated
with holes, and near the top there is inserted the small tube, _c_,
which conveys the gas down to a perforated expansion of the tube,
_d_, through the apertures of which the gas issues into the water
contained in A. Another tube, _e_, reaches near the bottom, and is
connected with a stop-cock for the purpose of drawing off the aerated
liquid. In charging the apparatus, the interior, A, is nearly filled
with water, or other liquid, through the opening, _f_, which is then
closed by cork, which is kept in its place by a screw nut. A few
ounces of carbonate of soda, mixed with water, are then poured into
the generator through the opening at _g_. The mixture flows through
the apertures in the partition, and occupies the lower part of the
generator. A proportionate quantity (about three-fourths of the weight
of the soda) of tartaric acid in crystals is then introduced through
_g_, which lodge on the top of the partition without touching the soda.
The opening being then closed by a screw-nut, the apparatus, which is
mounted on pivots, with an appropriate stand, is swung backwards and
forwards like a pendulum. The effect of this agitation is to force
a portion of the water saturated with carbonate of soda through the
apertures at _a_, where it comes in contact with the tartaric acid,
and instantly generates carbonic acid gas. The gas, having no other
escape than through the tube, _c_, is forced into the vessel A, and
becomes mingled with the water by the same act of vibration that brings
the soda and tartaric acid together. The continuance of the vibratory
action for a short time generates sufficient gas to aerate the water
or other liquid contained in the vessel, A. When the aeration is
completed, the soda-water may be drawn off, as required, through the
stop-cock. The apparatus is made of two sizes, to hold one and two
gallons.

[Illustration]

The tartaric acid and soda in the generator do not mingle with the
water, and the tartrate of soda, resulting from the combination, is
emptied after the soda-water is drawn off, before renewing the charge.

A French modification of this apparatus, in glass vessels protected by
cane netting, called a "gasogene," has recently been introduced, and is
extensively used. The materials for generating the carbonic acid gas
are put into the smaller vessels, and kept separate until the apparatus
is inverted, and then gas is rapidly generated, and forces itself
through the water.

The powders that are sold for making soda-water, by mixing them
together, consist of carbonate of soda and tartaric acid. When brought
together in solution, a violent effervescence ensues, but the gas is
not combined with the water in the same manner as when it is forced
in and allowed to remain for some time with the liquid to be aerated.
There is the further disadvantage attending such powders, that the
tartrate of soda, formed by the tartaric acid and the carbonate of
soda, employed to generate the gas, is drunk with the water.




REVOLVERS AND MINIE RIFLES.


"Is there anything whereof it may be said, See, this is new? it hath
been already of old time, which was before us."[18] This observation
of Solomon, the correctness of which we have often seen verified in
this History of Inventions, is applicable even to that great apparent
novelty the formidable "Revolver"--that death-dealing weapon, which
will fire six shots in rapid succession by merely pulling the trigger
so many times, as fast as it is possible.

The Revolver was almost unknown in this country until 1851, when it
was brought prominently into notice at the Great Exhibition, by the
specimens shown there by Colonel Colt, of the United States. Pistols
with six barrels, which might be fired successively with the same lock,
by turning them round, were, indeed, previously seen in gun-shops;
but their clumsy form and their great weight prevented them from
being used. Nor was Colonel Colt much more successful in his earlier
attempts to bring his Revolver into public notice. He obtained his
first patent in America in 1835, and established a manufactory for
the pistols at Paterson, United States, where he expended £35,000 in
attempting to bring the fire-arm to perfection, but with no beneficial
result to himself beyond gaining costly experience. He made further
improvements in 1849, and so far perfected the weapon that it had been
used extensively in America before it was brought into notice in this
country.

When Colonel Colt came to England, he undertook to investigate the
origin of repeating fire-arms, with a view to ascertain how far he had
been anticipated; and the result of his researches was, that repeating
fire-arms, similar in principle to his own Revolver, had been invented
_four centuries before_.

He found in the Armoury of the Tower of London a matchlock gun,
supposed to have been made as early as the fifteenth century, which
very closely resembles, in the principle of its construction, the
Revolver of the present day. It has a revolving breech with four
chambers, mounted on an axis fixed parallel to the barrel, and on
that axis it may be turned round, to bring any one of the four loaded
chambers in succession in a line with the barrel, to be discharged
through it. There are notches in a flange at the fore end of the
revolving breech to receive the end of a spring, which is fixed to the
stock of the gun, for the purpose of locking the breech when a chamber
is brought round into the proper position. The hammer is split at the
end, so as to clasp a match, and to carry its ignited end down to the
priming powder when the trigger is pulled. Each chamber is provided
with a priming pan that is covered by a swing lid, and, before firing,
the lid is pushed aside by the finger, to expose the priming powder to
the action of the lighted match. If the date of this gun be correctly
stated, a very rapid advance in the art of gunnery must have been made
after the invention of gunpowder, which took place only one hundred
years previously. The want of a better mode of discharging the gun than
a lighted match was one of the chief obstacles to the introduction of
the Revolver four centuries ago.

There is also in the Tower Armoury a specimen of a repeating fire-arm
of a more recent date, though still very ancient, that presents
considerable improvement on the preceding one. It has six chambers
in the rotating breech, and is furnished with a barytes lock and one
priming pan, to fire all the chambers. The priming pan is fitted with
a sliding cover, and a vertical wheel with a serrated edge projects
into it, nearly in contact with the powder in the pan. To this wheel a
rapid motion is given by means of a trigger-spring, acting upon a lever
attached to the axis of the wheel; and the teeth of the wheel strike
against the barytes, which is brought down, previously to firing, into
contact with it, and the sparks thus emitted set fire to the powder in
the priming pan, and discharge the piece. In this instance, also, the
breech is rotated by hand.

A still further advance towards perfection in repeating fire-arms is
to be seen in the United Service Museum, where there is a pistol,
supposed to have been made in the time of Charles I., with the breech
rotated by mechanical means. In this pistol, the act of pulling back
the hammer turns the breech, containing six chambers, one-sixth part
of a revolution, and the priming powder is ignited by a flint hammer
striking against steel.

The manufacture of these fire-arms presented some practical
difficulties which could only be overcome by great care and skill in
the construction; and from the failure in this respect they were not
patronized. It was necessary, in the first place, that the loaded
chambers should be brought into an exact line with the barrel, and be
firmly retained there during the discharge. It also required great
nicety in the fitting of the breech to the barrel, to prevent the fire
from communicating to the other chambers. A further difficulty was to
prevent the spindle, whereon the breech revolved, from becoming foul
by the explosion of the powder; otherwise, after firing a few times it
would stick fast, and the gun would become useless.

The earliest patent for repeating fire-arms in this country was
obtained by James Puckle, in 1718, for a gun with a rotating breech.
There were six chambers in the breech, which was turned round by a
winch, and, when the six were fired, there was an arrangement by
which the chambered breech could be removed, and another loaded one
substituted for it. Mr. Puckle appears to have been of a poetical
turn of mind, and the specification of his patent is enlivened by the
following loyal couplet, which deserves to be quoted as a novelty in
patent records:--

      "Defending King George, our country and laws,
      Is defending yourselves and the Protestant cause."

The invention of percussion priming in 1800, by the Rev. A. J. Forsyth,
was an important step towards the perfection of fire-arms generally,
and of Revolvers in particular; for until the chambered breech could
carry round with it in a compact form the priming for each chamber, the
construction must have been clumsy, and the action uncertain.

Colonel Colt, as already stated, took out his first patent in 1835,
and in 1849 he patented the improved Revolver, which he has brought
into general use. It has six chambers in the rotating breech, and the
nipples to hold the percussion caps are sunk into a recess, so that
the lateral fire, if any, cannot reach them; and at the other end, the
chambers are protected from lateral fire by chamfering their mouths. By
these means, the danger of firing the gunpowder in the other chambers
is effectually provided against.

The demand for Colt's Revolvers became so great after the last
improvements were made, that at his manufactory, at Hartford, in
America, he made 53,000 of them in 1853; and at his manufactory at
Vauxhall, near London, he employs upwards of 300 workmen, though by far
the largest portion of the work is done by machinery.

Several improvements have been introduced in Revolvers since Mr. Colt's
patent of 1849, among which is the arrangement, made by Mr. Adams in
1851, for causing the chambered breech to turn by the action of pulling
the trigger, which at the same time draws back the hammer. By this
arrangement, the whole of the six loaded chambers may be discharged in
three seconds, whilst the pistol continues presented.

The latest improvements in Revolvers were contrived by Mr. Josiah Ells,
of Pittsburg, North America, as specified in a patent obtained for him
by the author, in his own name, in 1855. The annexed woodcuts show the
figure of this Revolver, with the working parts round the lock exposed
to view, together with the shape of the revolving chambered breech.

[Illustration]

In this improved Revolver, the force required to pull back the hammer,
_a_, is regulated by a double spring, _w_, so as to diminish as the
hammer is drawn back; and at the moment of firing a slight pull of the
trigger is sufficient. Another improvement consists in the addition
to the chambered breech, _d_, of a projecting tube, which prevents
the spindle on which it turns from becoming foul; and there is also a
safety bolt added, as a protection against accidental firing.

The plan of making the mere action of drawing the trigger turn the
chambered breech and pull back the hammer, as originally contrived by
Mr. Adams, required so much force to pull the trigger as to interfere
materially with the accuracy of aim. There was danger, also, in that
mode of turning the chambered breech, arising from premature firing. In
Mr. Ells's Revolver these objections are in a great measure obviated;
first, by the action of the double spring, by which the force required
is diminished as the trigger is pulled farther back; and in the second
place, by making the shoulder of the hammer catch into a small notch,
which holds it at full cock, until, by a further pull of the trigger,
the pistol is fired.

An improvement in the art of war, no less important than the Revolver,
was introduced nearly at the same time. The Revolver affords a
formidable means for attack or defence at short distances, whilst the
Minié Rifle extends the destructive range of fire-arms far beyond the
distance to which the ordinary musket ball could reach. The principle
of rifling gun barrels was first made known in the specification of
an invention patented in 1789, by Mr. Wilkinson, the improvement he
effected being thus described:--"The gun, or piece of ordnance, after
being bored in the usual method, hath cut therein two spiral grooves,
which run the whole length of the bore. These curves, according to
their curvature, will give a circular motion to the shot during its
flight."

The spiral grooves, when the bullets are rammed down, cause the ball
to offer greater resistance, therefore the explosive force of the
gunpowder is brought to act upon them more completely before they leave
the gun barrel; and the rotary motion imparts greater steadiness to the
ball. Rifled barrels, therefore, carry the balls farther, and increase
the accuracy of the aim. They, however, require increased power and
longer time to ram down the ball in loading, and the risk of bursting
the gun is increased if the ball be not rammed close upon the powder.
For these reasons, they were considered unfit to be employed generally
by soldiers, and they were entrusted only to select corps of rifle
shooters. The object of Captain Minié's invention was to facilitate
the loading of rifles, by contriving a bullet which might be easily
rammed in, and would expand in the act of firing, so as to fill up the
grooves. What is commonly called the Minié Rifle is, in fact, only a
Minié Rifle Ball, for the barrels of the guns are nearly the same as
the ordinary grooved rifles.

The ball is an elongated one, with a hollow cone at the bottom, into
which is fixed an iron button. When the gun is fired, the button is
forced into the cone, and expands the lead, which thus fills up the
grooves and gives a spiral direction to the bullet. The Minié ball
serves the purpose excellently for a short time, but after firing
several rounds the iron button is forced through the lead, leaving a
portion of it behind, which clogs up the barrel, and renders it unfit
for use.

Several substitutes for iron were tried, to remove that inconvenience,
and it was at length found that the button might be dispensed with
altogether, for the hollow cone is of itself sufficient to expand
the lead. The balls are, therefore, now made in that manner at the
Government gun manufactory at Enfield, and the rifled guns now used in
the army, which carry bullets to the distance of a mile and more, are
called the _Enfield Rifle_. The cost of each of these rifles to the
Government is stated to be £3 4s. 7½d. As the balls are made to slip
into the barrels easily, they can be loaded as readily as the common
musket: and they will carry three times the distance, with much more
certainty.




CENTRIFUGAL PUMPS.


Many ingenious men have vainly attempted to apply what has been
erroneously called "centrifugal force" as a motive power, conceiving
that the effort made by bodies to fly off when whirled round in a
circle was occasioned by a force generated by their rotation. The
experiment of the "whirling table," which is commonly shown to
illustrate centrifugal action, tends to confirm the notion that force
is generated; for it is there seen that, when the velocity of rotation
is doubled, the centrifugal force is quadrupled, and that it continues
to increase in a geometrical ratio. It has, therefore, been conceived
that a power might be generated of indefinite amount; for as a double
velocity can be communicated by doubling the moving power, whilst the
tendency to fly off at the circumference is quadrupled, there appeared
to be a creation of power which, if properly applied, would realize
perpetual motion.

A working engineer known to the author was so fully possessed with
the notion that power might thus be created, and that its application
would be of the utmost benefit, that he imagined he had been specially
appointed to reveal the principle to man, as a boon of inestimable
value to the manufacturing arts. The plan he adopted was to employ
what he called a generating engine, consisting of a centrifugal pump;
and the force with which the water was projected from the ends of
two rotating horizontal arms was directed against pistons working in
cylinders, as the force of steam is in a steam engine. Having once
set this machine in action, he expected to be able, by means of the
self-creating centrifugal force, to generate the power that worked
the generating engine, and thus to have a reservoir of force of any
magnitude constantly at command. So completely satisfied was he of
the practicability of the plan, founded, as he supposed, upon one of
Newton's laws of motion, and he felt so happy in the thought of being
charged with an important mission for the benefit of mankind, that it
was almost cruel to attempt to correct his notions of the power of
centrifugal force. He spent all his money in endeavouring to realize
this impossible project, and even its failure did not convince him of
his error.

The simple kind of Centrifugal Pump applied in that chimerical scheme
was known upwards of one hundred years ago. It consisted of a vertical
hollow shaft, into which were inserted two horizontal arms. The shaft
was supported on a pivot at the bottom, and was turned by a handle at
the top, as represented in the accompanying drawing. The lower end
of the vertical shaft was immersed in water, and when rotary motion
was given to the machine, the centrifugal action propelled the water
from the ends of the arms, and the water rose in the vertical shaft to
supply its place.

[Illustration]

The effect in a pump of this construction is due to the pressure of
the atmosphere, for the outpouring of the water from the rotating arms
tends to produce a vacuum in the shaft, in the same manner as the
lifting of the plunger in a common pump. It is evident, therefore,
that a Centrifugal Pump of that construction could not raise a column
of water higher than the pressure of the atmosphere would force it up,
which would be about thirty feet.

[Illustration]

Mr. Appold's Centrifugal Pump, which constituted one of the most
remarkable features of the Machinery Department of the Great
Exhibition, is constructed on a different plan, though the principle
is the same. The rotating arms are immersed in the water to be raised,
and to diminish the resistance which would be produced by the rotation
in water of two or more exposed arms, they are enclosed within discs of
metal, about one foot in diameter, and three or four inches apart. The
arms are formed by curved partitions between the discs, which radiate
from the centre to the outer rim, towards which the space between the
discs is contracted. This pump is fixed on an axis, to which rapid
rotary motion can be given; and it is fitted into a case connected with
the pipe that conveys the water to the discharging orifice. The water
enters the rotating disc through a large aperture in the centre, and it
is forced through the spaces formed by the radical arms with increasing
velocity, until it escapes from the circumference. Sections of Mr.
Appold's pump are shown in the accompanying diagrams, in which A is the
central opening for the admission of water; C, C, C, the curved radical
partitions which form the arms by which motion is communicated to the
water, and through the ends of which it issues into the external case,
connected with the lift-pipe, D.

In the Great Exhibition there were two other Centrifugal Pumps shown
in action, one by Mr. Bessemer, and one by Mr. Gwynne, from America;
but neither of them exhibited such striking effects as Mr. Appold's,
which was so arranged as to throw out a continuous cascade of water
from an aperture six feet wide, at a height of twenty-six feet. The
Jury of Class V., who made numerous experiments to determine the
practical efficiency of Centrifugal Pumps, and the relative merits of
the three exhibited, reported very favourably of that of Mr. Appold,
to whom a Council Medal was awarded. When rotating at the rate of 788
revolutions in a minute, and lifting the water 19·4 feet, the greatest
practical effect, compared with the power employed, was attained. The
discharge of water per minute at that height, with the pump rotating
with a velocity of 788 revolutions, was 1,236 gallons; and with a
lift of 8 feet, 2,100 gallons per minute were discharged, when the
rotating velocity was 828 revolutions per minute. In Mr. Gwynne's and
Mr. Bessemer's pumps, which had straight vanes, the ratio of power to
the effect did not exceed 0·19. One of Mr. Appold's pumps, only one
inch in diameter (the exact size of the small diagram), will discharge
ten gallons per minute. The greatest height to which water has been
raised by the pumps that are one foot in diameter is 67·7 feet, with a
velocity of 4,153 feet per minute.

The velocity with which the pump should revolve depends upon the
height to which the water is to be raised. Beyond a certain height,
the required velocity is practically unattainable, but long before
that limit is reached the waste of power becomes so great, that the
pump is of no value, for the pressure on the circumference counteracts
the force with which the water is expelled. It is, therefore, only
at comparatively low levels that the Centrifugal Pump is a useful
engine. The absence of all valves renders it very suitable for draining
marshes, and for other similar purposes, as the muddy water and
suspended matters will not obstruct its action.

In the Report of the Jury the influence of the curved shape of the
radial arms is considered very important in producing the effects.
"If the vanes be straight," the Report observes, "it is evident, that
whatever may be the velocity of the water in the direction of a radius,
when it leaves the wheel its velocity in the direction of a tangent
will be that of the circumference of the wheel, so that the greater
the velocity of the wheel the greater will be the amount of _vis viva_
remaining in the water when discharged, and the greater the amount of
power uselessly expended to create that _vis viva_. If, however, the
vanes be curved backwards as regards the motion of the wheel, so as
to have nearly the direction of a tangent to the circumference of the
wheel at the points where they intersect it, the velocity due to the
centrifugal force of the water carrying over the surface of the vane in
the opposite direction to that in which the wheel is moving, and nearly
in the direction of a tangent to the circumference, will--if this
velocity of the water over the vane in the one direction be equal to
that in which the vane is itself moving in the other--produce a state
of absolute rest in the water, and entire exhaustion of _vis viva_." It
is an interesting fact in the history of the invention, that the curved
form was formerly adopted in some of the American pumps, and afterwards
abandoned.

There are competing claims to the invention of Centrifugal Pumps in
the form now adopted. This kind of pump is stated to have been used in
America in 1830. M. Charles Combe took out a patent in France for a
similar pump in 1838; but though Mr. Appold was later in the field with
his more perfect machine, he appears to have proceeded independently of
previous inventors.




TUBULAR BRIDGES.


No sooner had the formation of railways commenced for carrying
passengers in long trains of carriages drawn by heavy locomotive
engines, than the want was experienced of some different kind of bridge
from any then existing for crossing rivers, roads, and valleys. The
train could not be turned sharply round a curve to cross a road at
right angles; and to make the requisite bend to enable it to do so
would have taken the railway considerably out of its direct course. To
overcome this difficulty "skew bridges" were designed, that crossed
roads and canals in slanting directions. Iron girder bridges were also
constructed, and thus the railway trains were carried across roads and
narrow rivers at any required inclination, supported on flat beams of
iron. Suspension bridges were found to be unfitted, on account of their
oscillation, for the passage of locomotive engines; therefore, when
it became necessary to carry railways across arms of the sea, or wide
navigable rivers, at heights sufficient to allow the largest ships to
pass underneath, neither girder bridges nor suspension bridges were
suited for the purpose. Then arose the necessity of contriving some
form of bridge of extensive span that would be sufficiently strong and
rigid for railway trains to pass over them in safety.

The Britannia Bridge, across the Menai Straits, was a triumphant
response to the call for a new kind of suspended roadway adapted to
the requirements of railways. The tubular principle of construction,
designed by Mr. Robert Stephenson, was practically tested by Mr.
Fairbairn; and the result of numerous experiments on the strength of
iron, in different forms and combinations, established the soundness
of that principle. The rigidity and strength of the Britannia Bridge
depend on cellular cavities at the top and bottom, which, acting as so
many tubes, give stability to the riveted plates of iron, and enable
the bridge to bear the immense pressure and vibration of a heavy
railway train without deflecting more than half an inch.

It was Mr. Stephenson's original intention to make a circular or oval
tube, suspended by chains, for the trains to run through; but Mr.
Fairbairn's experiments proved that a rectangular shape is stronger,
provided the top and bottom, which bear the greatest part of the
strain, are made rigid, either by additional plates of iron, or by
tubes. The notion of a circular tube was, therefore, abandoned, and the
rectangular form, with cells at the top and bottom, was adopted; first
for the railway bridge at Conway, and afterwards for the much greater
work across the Menai Straits.

It has been stated by Mr. Stephenson, that the idea of forming a
tubular bridge was suggested by experience gained in constructing the
railway bridge at Ware, which consisted of a wrought-iron cellular
platform; but a more exact representation of the principle on which
the Britannia Bridge is constructed had been long previously seen
across the Rhine, at Schauffhausen, where a rectangular tube, or
hollow girder, made of wood, was erected in 1757. That bridge, though
of different material, was in its principle of construction similar
to the iron tubular bridges at Conway and at the Menai Straits.
Another similar bridge, carried over the river Limmat, at Wettingen,
constructed in 1778, had a span of 390 feet; and that, as well as the
former, was raised to its position in one piece, by means of powerful
screw-jaws. These curious and interesting structures, which may be
considered the forerunners of the gigantic iron Tubular Bridges of the
present day, were burnt by the French in 1799.

In constructing the Britannia Bridge, Mr. Stephenson took advantage
of a rock midway from shore to shore, whereon to erect the central
pier. Two other piers, at a distance, on each side, of 460 feet, were
built without much difficulty in shallower water, and between these
and the masonry on each side was a distance of 230 feet. There are
eight rectangular tubes resting on those piers, to form two lines of
railway, each tube being 28 feet high and 14 feet wide, exclusive
of the cellular cavities at the top and bottom. These cavities are
rectangular, and extend from one end of the bridge to the other, and
may be regarded as long tubes. There are eight of them at the top, each
1 foot 9 inches square, and there are six at the bottom, the latter
being 2 feet 4 inches wide, and the same depth as those at the top.
Sound is conveyed through these cavities as readily as through speaking
tubes, and conversation can be thus easily carried on across the
Straits.

The height of the central pier of the Britannia Bridge, from the
foundation to the top, is 230 feet; and the height of the roadway above
high water mark is 104 feet. The length of the large tubes, through
which the railway carriages pass, on each side of the central pier, is
460 feet: and the total length from shore to shore, 1,531 feet. The
tubes are connected together at the piers to give the bridge additional
strength, and they are composed altogether of 186,000 separate pieces
of iron, which were pierced with seven millions of holes, and united
together by upwards of two millions of rivets. The whole mass of iron
employed weighed 10,540 tons.

The Britannia Bridge was commenced in May, 1846, and the first of the
main tubes was completed in June, 1849. The work was carried on close
to the bridge, on the Anglesea shore; and when the tube was ready to
be transported to its place on the piers, which had been prepared to
receive it, eight flat-bottomed pontoons were provided to carry it,
which, being brought underneath, floated the ponderous mass on the
water as they rose with the tide.

The floating and fixing in its place of the tube took place on the
27th of the same month, in view of an immense concourse of spectators.
After the preliminary arrangements for letting go had been completed,
Mr. Stephenson, and other engineers, got on the tube, with Captain
Claxton, R. N., to whom the management of the floating was entrusted.
A correspondent of the _Illustrated London News_ thus describes the
proceeding, and its successful result:--"Captain Claxton was easily
distinguished by his speaking trumpet, and there were also men to hold
the letters which indicated the different capstans, so that no mistake
could occur as to which capstan should be worked; and flags, red,
blue, and white, signified what particular movement should be made.
About 7.30 p.m. the first perceptible motion, which indicated that
the tide was lifting the mass, was observed, and at Mr. Stephenson's
desire, the depth of water was ascertained, and the exact time noted.
In a few minutes the motion was plainly visible, the tube being fairly
moved forward some inches. This moment was one of intense interest,
the huge bulk gliding as gently and easily forward as if she had been
but a small boat. The spectators seemed spellbound, for no shouts or
exclamations were heard, as all watched anxiously the silent course of
the heavily freighted pontoons. The only sounds heard were the shouts
of Captain Claxton, as he gave directions to 'let go ropes,' to 'haul
in faster,' &c.; and 'broadside on,' the tube floated majestically
in the centre of the stream. I then left my station, and ran to the
entrance of the works, where I got into a boat, and bade the men pull
out as far as they could into the middle of the Straits. This was
no easy task, the tide running strong; but it afforded me several
splendid views of the floating mass, and one was especially fine; the
tube coming direct on through the stream--the distant hills covered
with trees, two or three small vessels and a steamer, its smoke
blending well with the scene, forming a capital background; whilst on
one side, in long stretching perspective, stood the three unfinished
tubes, destined ere long to form, with the one then speeding on its
journey, one grand and unique roadway. It was impossible to see this
grand and imposing sight, and not to feel its singleness, if we may so
speak. Anything so mighty of its kind had never been before: again it
would assuredly be; but it was like the first voyage made by the first
steam-vessel--something until then unique. At 8.35 the tube was nearing
the Anglesea pier, and at this moment the expectation of the spectators
was greatly increased, as the tube was so near its destination: and
soon all fears were dispelled, as the Anglesea end of the tube passed
beyond the pier, and then the Britannia pier end neared its appointed
spot, and it was instantly drawn back close to the recess, so as to
rest on the bearing intended for it. There was then a pause for a few
minutes, while waiting for the tide to turn: and when that took place,
the huge bulk floated gently into its place on the Anglesea pier,
rested on the bearing there, and was instantly made fast, so that it
could not move again. The cheering, till now subdued, was loud and
hearty, and some pieces of cannon on the shore gave token, by their
loud booming, that the great task of the day was done."

The tube, when in position, was lowered down upon its bearings on the
pier by opening valves in the pontoons, which thus sunk sufficiently to
ease them of their load.

The work of raising the tube to its position, 100 feet above high
water mark, was a much slower operation, and was attended with serious
difficulties. Hydraulic presses were used for the purpose, placed at
the top of the piers; two smaller ones, which had served to raise the
Conway Bridge, being at one end, and a much larger press, made for
the occasion, being fixed at the other. The immense tube was lifted
by chains fixed to the heads of the presses, and two steam engines,
of 40-horse power each, were employed to force the water into the
cylinders. The diameter of the ram of the largest hydraulic press
was 20 inches, and the pressure upon it was equal to 2¼ tons on each
circular inch. The tube was raised by successive lifts of 6 feet each,
and, as it was lifted, the space was built in with masonry for its
ultimate bearing. During the operation of lifting, the bottom of the
cylinder of the large hydraulic press burst out, and fell on the top of
the tube, in which it made a considerable indentation. Mr. Stephenson
had provided against the possibility of such accident, by having blocks
of wood, an inch thick, introduced under the tube as it was elevated,
and these blocks arrested its fall, or it would otherwise have been
dashed to pieces. Even the small fall of an inch did considerable
injury. This accident caused some delay, but the other tubes were in
the meantime progressing, and the completed bridge was opened for
public traffic on the 21st of October, 1850.

The strength of the bridge was tested before passenger trains were
allowed to pass through it, by placing in the centre of the longest
tubes twenty-eight waggons, loaded with 280 tons of coal, and two
locomotives, and by afterwards sending those heavy trains through
the bridge at full speed. The deflection of the tubes in the centre
amounted to only three-quarters of an inch in each cell; it being
rather less when the trains were at full speed than when stationary.
The strongest gusts of wind to which the bridge has been exposed
have not caused a vibration of more than one inch. The total cost of
construction was £601,865; of which sum £3,986 was for experiments, and
£158,704 for masonry.

Another Tubular Bridge of rival magnitude to the one across the Menai
Straits is now in the course of construction by Mr. Brunel across the
Tamar, at Saltash, for the South Devon and Cornwall Railway. As no
rock presented itself conveniently halfway across whereon to erect
the central pier, Mr. Brunel was obliged to work at a great depth
below the surface of the water in making the foundation of the Royal
Albert Bridge. In the plan of making the foundation, as well as in the
structure of the bridge itself, Mr. Brunel adopted a course altogether
original. Instead of attempting to construct a coffer-dam by piles,
which would have been almost impracticable at such a depth, and very
costly, he caused a large iron tube to be put together, thirty-six feet
in diameter, and ninety-six feet long, to reach to the bed of the
river. This monster tube was lowered perpendicularly in the middle of
the river, and the water being pumped out of it, the men could work at
the bottom in safety. In this manner, after much labour, the rock was
prepared to receive the blocks of granite, which were laid one on the
other, till they rose above the surface of the water. On that granite
pedestal a cast-iron pier was raised to a height of 100 feet, the level
of the roadway of the rails.

The cast-iron pier consists of four octagon columns, 10 feet in
diameter. They stand about 10 feet apart, forming a square, and they
are bound together by massive lattice-work of wrought iron, to prevent
any lateral movement. Each of these columns weighs 150 tons; and when
the full weight of the bridge rests on the foundation of the central
pier, the pressure will be equal to 8 tons on the square foot, or
double the pressure of the Victoria Tower on its base.

In the structure of the bridge, Mr. Brunel availed himself of the
results of the experiments made by Mr. Fairbairn on the strength of
iron tubes, but he adopted a very different plan from that of Mr.
Stephenson. Instead of constructing a large tube for the trains to pass
through, Mr. Brunel made tubular arches, consisting of iron plates
curved and riveted together, to serve as rigid supports, from which the
roadway is suspended by chains and by connecting iron bars.

The placing of the first of the tubular arches in position between the
pier near the shore at Saltash and the central pier, which took place
on the 1st of September, 1857, excited great interest, and at least
50,000 persons were assembled from places far and near to witness
the operation. The tube, with the roadway and suspension chains, was
floated from the yard where it was put together on four pontoons; and
it was thus conveyed, and safely deposited on the piers at a height of
30 feet above high water mark. It was afterwards gradually raised by
hydraulic presses to the top, a height of 100 feet. The work of raising
it commenced on the 25th of November, and was completed on the 19th of
May last.

The following lively description of the Royal Albert Bridge, and
its surrounding scenery, extracted from a recent article in the
_Times_, gives a very good idea of the magnitude of the structure, by
comparison with well-known objects:--"Though, probably, our readers
may care little and have heard less about Saltash proper, it is
likely henceforth to receive a fair share of general attention, and
we can safely say, to those who will journey down to see the bridge,
that the viaduct requires indeed to be a fine one to attract their
attention from the lovely scenery of the valley of the Tamar, which
it crosses. The banks of this noble river narrow in considerably as
the stream reaches Saltash, and, hemmed in there to half a mile or so,
suddenly widens out into as fine a sheet of water as any of its kind
in the kingdom, its distant banks covered with cottages, and fringed
with undulating woodlands down to the very edge. Across this narrow
part of the channel, where Saltash, in picturesque dirt and disarray,
straggles up the banks on one side, and a steep hill, covered with
rock and rock-grown underwood, forms the other, the viaduct stretches
high in air. The briefest general way of describing it is to say that
it consists of nineteen spans or arches, seventeen of which are wider
than the widest arches of Westminster Bridge; and two, resting on a
single cast-iron pier of four columns in the centre of the river, span
the whole stream at one gigantic leap of 910 feet, or a longer distance
than the breadth of the Thames at Westminster. The total length of the
structure from end to end is 2,240 feet,--very nearly half a mile, and
300 feet longer than the entire stretch of the Britannia Bridge. The
greatest width is only 30 feet at basement; its greatest height from
foundation to summit no less than 260 feet, or 50 feet higher than the
summit of the Monument. The Britannia Bridge, both in size, purpose,
and engineering importance, seems to offer the best comparison with
that of Saltash, but the similarity between the structures is far from
being as great as might be at first supposed. The Britannia tube is
smaller, and cost nearly four times the price of the Saltash Viaduct,
though the engineers had natural facilities which Mr. Brunel, for his
Cornish bridge, certainly had not."

The form of the tubes is an oval, 17 feet in its longest diameter,
and 12 feet in its shortest. They are bent into an elliptical curve,
with a rise in the middle of twenty-eight feet. With the roadway and
suspension chains attached, each tube weighs 1,100 tons. The total
weight of wrought iron in the bridge, when completed, will be 2,650
tons; of cast iron, 1,200; of masonry and brickwork there will be
about 17,000 cubic yards; and of timber, about 14,000 cubic feet.

The second tube, which is in every respect like the first, was
completed on the 30th of June last, and on the 10th of July was
successfully placed in position between the central pier and the
Devonshire side of the river. The operation of elevating it began on
the 9th of August, and it has now reached nearly the level of the first
one, the tube being raised six feet in a week.

The engraving on the other side is a view of this wonderful structure
in its completed form. Its appearance is far more light and elegant
than that of the Britannia Bridge, but it remains to be seen whether it
will be equally steady under a gale of wind, and whether any vibration
of the suspended roadway will interfere with the rapid motion of the
trains. As the South Devon Railway has only one line of rails for the
greater portion of its length, but a single roadway is provided on the
Royal Albert Bridge.

The progress of railway locomotion has not only given rise to the
construction of new kinds of bridges, but it has directed mechanical
science to devise better means of applying the strength of materials.
On the South Devon and Cornwall Railways are to be seen wooden
viaducts, carrying the line over valleys at great heights, constructed
with such slender timbers, that, to an inexperienced eye, they seem
frightfully frail for the support of heavy railway trains.

[Illustration: ROYAL ALBERT BRIDGE, OVER THE TAMAR, AT SALTASH.]

We must not omit to notice, among the remarkable bridge erections
connected with railways, the viaduct across the valley of the Boyne,
which passes over the river close to the town of Drogheda, at a height
of 95 feet. The central portion of the viaduct is supported on four
piers, 90 feet above high water mark, with a span in the centre of
250 feet, and on each side of 125 feet. This elevated portion of the
work is approached on the southern side by twelve arches, of 60 feet
span each, and on the north by three similar arches. The viaduct is
constructed of limestone and iron lattice-work, and is calculated to
bear 7,200 tons.

During the erection of this viaduct the railway trains were carried
over the valley on a wooden platform, without side railings, supported
by scaffold-poles; and the crackling of the timbers, as the carriages
passed over it, and the dizzy height at which they were carried through
the air, produced a sensation of terror in nervous passengers, that was
fully justified by the apparent danger.




SELF-ACTING ENGINES.


The manufacturing progress of this country has depended, in a great
degree, on the facility possessed of making machinery of all kinds by
the aid of powerful engines worked by steam power. These engines, most
of which appear to be self-acting, forge and roll and cut and bore
beams of iron, boiler plates, and cylinders of immense size, which
it would be impossible to make by hand; and they do the work with a
rapidity and mechanical accuracy that would be otherwise unattainable.
In the progress of manufacturing invention, the small steam engine
first made by manual labour created the power to make other steam
engines of large size; and those more powerful engines supplied the
means of making still larger shafts and cylinders for engines that were
to be employed in the construction of machines of various kinds, to be
worked by the power thus accumulated.

The important advantages derived from the invention and application of
self-acting machinery, not only by the community at large, but even
by the workmen whose labour they for a time superseded, were forcibly
stated by Mr. Whitworth, in his opening address at the Institution of
Mechanical Engineers, in September, 1856:--"I congratulate you," he
observed, "on the success which in our time the mechanical arts have
obtained, and the high consideration in which they are held. Inventors
are not now persecuted, as formerly, by those who fancied that their
inventions and discoveries were prejudicial to the general interest,
and calculated to deprive labour of its fair reward. Some of us are
old enough to remember the hostility manifested to the working of the
power-loom, the self-acting mule, the machinery for shearing woollen
cloth, the thrashing machine, and many others. Now the introduction of
reaping and mowing machines, and other improved agricultural machinery,
is not opposed. Indeed, it must be obvious, to reflecting minds, that
the increased luxuries and comforts which all more or less enjoy,
are derived from the numerous recent mechanical appliances and the
productions of our manufactories. That of our cotton has increased
during the last few years in a wonderful degree. In 1824, a gentleman
with whom I am acquainted sold on one occasion 100,000 pieces of
74-reed printing cloth at 30s. 6d. per piece of 29 yards long; the
same description of cloth he sold last week at 3s. 9d. One of the most
striking instances I know of the vast superiority of machinery over
simple instruments used by hand, is in the manufacture of lace, when
one man, with a machine, does the work of 8,000 lace makers on the
cushion. In spinning fine numbers of yarn, a workman in a self-acting
mule will do the work of 3,000 hand-spinners with the distaff and
spindle.

"Comparatively few persons, perhaps, are aware of the increase of
production in our life-time. Thirty years ago, the cost of labour for
turning a surface of cast iron, by chipping and filing with the hand,
was 12s. per square foot--the same work is now done by the planing
machine at a cost for labour of less than one penny per square foot:
and this, as you know, is one of the most important operations in
mechanics; it is, therefore, well adapted to illustrate what our
progress has been. At the same time that this increased production
is taking place, the fixed capital of the country is, as a necessary
consequence, augmented; for in the case I have mentioned, of chipping
and filing by the hand, when the cost of labour was 12s. per foot, the
capital required for tools for one workman was only a few shillings;
but now, the labour being lowered to a penny per foot, a capital in
planing machines for the workman is required which often amounts to
£500, and in some cases more."

Notwithstanding the great economy of labour by the self-acting machines
now employed for doing all kinds of work, it is gratifying to find
that it has not had the effect of throwing men out of employ; for
the increased demand, consequent on the facility of production, has
more than compensated for the substitution of automaton mechanism for
handicraft.

It is extremely interesting to visit a large engineering factory, and
to witness the ease with which the masses of crude metal are wrought
in various ways, and converted by a number of seemingly self-acting
engines into other engines and machines which are, in their turn, to
become the agents of the further development of the skill and ingenuity
of man. In the new Government factory at Keyham, near Devonport, which
we believe to be one of the largest establishments of the kind in the
world, most of those powerful engines of the best construction may
be seen in operation. The completeness of the arrangements redounds
much to the credit of Mr. Trickett, the chief engineer, under whose
supervision they were made; and a walk through the factory, which is
thrown open to public inspection, will well repay a journey of many
miles. A detailed description of all its machinery would fill a volume,
but we must now limit ourselves to a bare enumeration of some of the
most remarkable features.

Numerous machines of the largest size, placed under the cover of an
extensive and lofty roof, are employed in doing everything requisite
for the fitting out of the largest steam-ships in the British navy.
Shears, put in continuous motion by steam power, are seen moving
steadily up and down, and cutting through the thickest boiler plates
without the least apparent effort, the chisel-shaped knives that cut
the metal moving just the same whether they be dividing the air or
shearing iron. Punching engines, in like manner, force holes through
iron plates an inch thick. Shaping and planing machines pare off the
tough iron as if it were not harder than cheese. Riveting machines
of different kinds bind together the plates of monster boilers with
marvellous rapidity; whilst machines for boring, for drilling, for
forging, and for doing every variety of smaller work, are to be seen
in operation in various parts of the factory.

Among the smaller self-acting engines, the forging machine for making
bolts attracts attention by the rapidity of its action. It consists of
a series of hammers placed side by side, so constructed as to shape
small bars of iron into any required form, according to the mould
of the swages beneath them, representing miniature anvils. It is
interesting to watch how readily the hot iron receives its shape under
the action of the hammers, which make about 700 strokes per minute,
the work being transferred from one to another to be progressively
finished. There is a circular saw that cuts through bars of iron
as thick as railway rails, by making upwards of 1,000 revolutions
per minute. A rivet-making machine forms the rivet, and shapes the
head to the requisite size, with great accuracy and quickness. There
are compound drilling machines, in which six drills are acting
simultaneously; hydraulic presses, that force parts of machines
together, and a great variety of other engines for the saving of time
and labour.

Not the least curious of the smaller contrivances is an apparatus which
deserves notice as a useful application of magnetism to manufacturing
purposes. Several horse-shoe magnets are attached to two endless
chains, moving over suitable wheels, and inclined at an angle of 30
degrees. These magnets at the lower end of the chain, dip into a tub
containing the mixed brass and iron turnings and filings from the
lathes and other tools, and the pieces of iron, being attracted by the
magnets, are carried away and brushed off into a box, leaving the brass
behind to be remelted.

In one department of the building are immense foundry furnaces, where
metals are melted and cast, the blast of the fires being maintained
by large rotating fans, kept in action by a powerful steam engine,
by which also the other machines are worked. The foundry is most
conveniently contrived for casting works of any required size, fixed
and travelling cranes being so stationed and arranged as to carry the
ladles of liquid metal to any part of the floor.

In another department is the smithy, where the iron to be wrought
into shape is heated in forges; and near to the forges stand the
Steam-Hammers--those gigantic Cyclops of modern times, that strike
blows, compared with the force of which the blows of the fabled Cyclops
of antiquity were but as the fall of a feather.

Ranged in a row there are four of these ponderous engines, of various
sizes; the largest hammer being so heavy as to require the power of
four tons to lift it, and when falling from a height of 6 feet nothing
can withstand its crushing blow. Yet the force of this mighty giant is
so completely under control, and may be brought to act so gently, as
scarcely to crack a nut placed to receive its fall.

The invention of the steam-hammer was the result of necessity. The
shaft of a steam engine having to be made larger than usual, no hammer
then in action by water power was capable of forging it, and Mr.
James Nasmyth was applied to, to give his aid in contriving the means
of removing the difficulty. It was then that the idea of lifting the
hammer-block by the direct action of steam occurred to him, and by a
succession of extremely ingenious devices, he at length perfected the
steam-hammer, which has been pronounced to be one of the most perfect
artificial machines, and one of the noblest triumphs of mind over
matter that modern English engineers have yet developed.

The accompanying woodcut represents the largest of the four
steam-hammers in Keyham factory. The hammer-block, _a_, weighing four
tons, is guided in its ascent and fall by grooves in two massive
uprights, which hold the whole together. The hammer-block is lifted
by the piston-rod of the steam cylinder above it, which is made of
such diameter, that the pressure of the steam on the surface of the
piston may considerably overbalance the weight of the hammer-block, and
overcome the friction of the connecting mechanism. The cylinder of the
largest steam-hammer at Keyham is 18 inches diameter, which gives an
area of 254 square inches; and the pressure of the steam generally used
being fifty pounds on the square inch, the total steam pressure tending
to force the piston up, when the whole of it is brought to bear, is
equal to five tons and a half. The force of the blow of the hammer,
when falling from its greatest height, is equal to 144 tons.

By the arrangements of levers, screws, and pipes and valves, shown in
the engraving, the steam is first admitted under the piston, and thus
acts directly in forcing it up, with the heavy hammer-block attached to
the piston rod. When the block has been raised to the required height,
it strikes against the end of a lever, which then shuts off the steam,
and allows it to escape; whereupon the hammer falls with its full force
vertically on the anvil. The end of the lever which turns off the
steam may be adjusted at any height, according to the required force of
the blow, so that the hammer may fall from a height of six feet, or be
merely raised a few inches.

[Illustration]

The steam-hammer, in the early stages of its invention, required
an attendant to turn on the steam again at the end of each stroke,
but Mr. Nasmyth ingeniously contrived the means of rendering the
engine altogether self-acting, by causing the force of the collision
to release a spring that holds down the slide-valve; and by this
contrivance a continued and regular succession of blows is maintained
without any assistance.

Not only can the force of the blow be regulated by the height to which
the hammer is lifted, but the ponderous mass may be arrested in its
descent by admitting the steam under the piston, so that a skilful
manipulator can stop it within the eighth of an inch from the anvil.

The Steam Engine itself, by which all the self-acting mechanisms of
a large factory are put in motion, is, perhaps, after all, the most
wonderful of inventions; but it does not strictly come within our
province, for Watt had perfected his great work before the close of
the last century. It was, however, not much used, excepting for mining
purposes, until after the commencement of the present; and the inventor
himself had but a faint idea of the value and vast importance of the
motive power he had placed at the command of man. So little, indeed,
was the value of steam power appreciated in the early years of its
application, that no notice is taken of the steam engine in Beckmann's
History of Inventions, though Watt had completed his condensing engines
several years before that work was published; and Newcomen's steam
engine had been at work at least sixty years.

The history of the steam engine affords a striking example of the
gradual development of an invention from vague and chimerical
notions, into an accomplished fact of astonishing magnitude. As in
the electric telegraph the dreams of the alchemist are fully realized
by the applications of scientific discovery, so in the wonder-working
powers of the steam engine one of the visionary schemes sketched in
the "Century of Inventions" is practically extended far beyond the
conceptions of its fanciful projector. How little could Beckmann have
supposed that an invention, which he considered too insignificant to be
mentioned, would, in the course of fifty years, have revolutionized the
world! It may possibly be the same, before this century is closed, with
inventions that are now neglected or despised.

       *       *       *       *       *

The record in the preceding pages of some of the most remarkable
applications of science during the present century, exhibits an amount
of intelligence, of skill, and of power that seems, when viewed in its
completed form, to be superhuman. It is only by tracing each invention
to its source, and by noting the step by step advances by which it has
arrived at its present state, that we can bring ourselves to believe
that the great development of power and the display of ingenuity we
witness, can have been accomplished by ordinary men. This feeling of
admiration, at the results of human industry and inventive genius, was
strongly excited on passing through the wonderful collection of the
works of all nations in the Great Exhibition of 1851. After walking
through the long avenues, crowded with the most highly finished
manufactured goods, and with works of art, adapted to every purpose
and capable of gratifying every luxurious taste of highly civilized
life, we beheld, in another part of the building, the self-acting
machines by which many of those productions had been manufactured. We
saw various mechanisms, moving without hands to guide them, producing
the most elaborate works; massive steam engines,--the representatives
of man's power,--and exquisite contrivances, displaying his ingenuity
and perseverance; and we felt inclined to exalt the attributes of
humanity, and to think that nothing could surpass the productions there
displayed. But as if to repress such vainglorious thoughts, there
stood in the transept of the building, surrounded by and contrasting
with the handiworks of man, one of the simplest productions of Nature.
Every single leaf on the spreading branches of that magnificent tree
exhibited in its structure, in its self-supporting and self-acting
mechanism, and in the adaptation of surrounding circumstances for its
maintenance, an amount of intelligent design and contrivance and
power, with which there was nothing to compare. After examining the
intricate ramifications of arteries and veins for spreading the sap
throughout the leaf, and the innumerable pores for inhaling and exuding
the gases and moisture necessary for its continued existence; after
carrying the mind beyond the beautiful structure itself, to consider
the provisions of heat and moisture and air, without which all that
mechanism would have been useless; and having reflected on the presence
of the mysterious principle which actuated the whole arrangement of
fibres, and gave life to the crude elements of matter,--we could not
fail to be impressed with the insignificance of the most elaborate
productions of man, when compared with the smallest work of the
Omnipotent Creator.


THE END.




FOOTNOTES:


[1] British Association Report for 1853.

[2] The original photographs produced by M. Niepce are still preserved
in good condition, and were last year exhibited at the Royal
Institution.

[3] "Philosophical Magazine," February, 1843.

[4] Brewster's Encyclopædia, article "Kaleidoscope."

[5] "The Stereoscope: its History, Theory, and Construction," by Sir
David Brewster.

[6] Primary signals are those in which the letter indicated is
represented by a single deflection of the needles in either direction.
A single needle telegraph can have only two primary signals, one to
the right and one to the left; all the other letters being indicated
by repeated deflections. In several instances four deflections are
required to signal a single letter.

[7] "Manual of Electricity," p. 251; and Reports of the Proceedings of
the British Association for 1851 and 1854.

[8] "Manual of Electricity," second edition, p. 247.

[9] "Treatise on Coal Gas," by Samuel Clegg, jun.

[10] See article, "Steam Carriages," page 35.

[11] It is stated in Mr. Clegg's "Treatise on Coal Gas," that Mr.
Clegg, sen., lighted the cotton mill of Mr. Henry Lodge, at Sowerby
Bridge, near Halifax, a fortnight before the mill of Messrs. Phillips
and Lee was so lighted. A friendly spirit of emulation is said to have
existed between Mr. Murdoch and Mr. Clegg in lighting those two mills
with gas, each one endeavouring to complete the work before the other.

[12] The facility with which a supply of carburretted hydrogen gas can
be obtained from gas works, induces aeronauts to fill their balloons
with it rather than be at the trouble and expense of making hydrogen
for the purpose; but the ascending power of the balloon is thereby
greatly diminished.

[13] _Journal of Gas Lighting_, vol. ii.

[14] Mr. Hearder, of Plymouth, affords a remarkable instance of the
successful pursuit of science under difficulties. He lost his sight in
his youth by an accidental explosion during some chemical experiments,
but instead of being disheartened by that calamity, he has continued to
pursue his investigations with unabated vigour, and has succeeded in
throwing much light on many of the recondite properties of electricity,
by admirably contrived experiments, which were conducted with
unremitting perseverance at great expense. He has been in the habit of
delivering lectures at the Plymouth Institution, and other Institutions
in Devon and Cornwall; and those who witness the skilful manipulation
of his experiments can scarcely suppose that he is blind.

[15] This statement does not adequately represent the reduction in
price; for each volume, sold at 5s., contained a volume and a half as
originally published, besides Sir Walter Scott's notes; and the cheap
volumes were illustrated with steel engravings.

[16] If the number of sheets of paper used in printing these works were
laid side by side, they would extend nearly _fifty thousand miles_!

[17] "L'Art de la Lithographie;" par M. Aloys Senefelder, Inventeur de
l'Art Lithographique. Munich, 1859.

[18] Book of Ecclesiastes i. 10.




Works on Chemistry.


Class-book of Chemistry.

BY E. L. YOUMANS.

12mo. 340 pages. Price 75 cents.

Every page of this book bears evidence of the author's superior ability
of perfectly conforming his style to the capacity of youth. This is a
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(owing to the rigid and technical manner in which it is presented), Mr.
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matter belonging exclusively to physicians and professors.

_From_ PROF. WM. H. BIGELOW.

  The eminently practical character of the Class-book, treating of
  the familiar applications of the science, is, in my opinion, its
  chief excellence, and gives it a value far superior to any other
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_From_ DAVID SYME, A. M., _formerly Principal of the Math. Dept. and
Lecturer in Nat. Philosophy, Chemistry, and Physiology, in Columbia
College_.

  MR. YOUMANS: Dear Sir,--I have carefully examined your Class-Book
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_From_ PROF. J. MULLIGAN, _Principal of Young Ladies' School, New York_.

  We have a large number of school-books for the purpose of giving
  elementary instruction in Chemistry--possessing various kinds and
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Chemical Chart:

BY E. L. YOUMANS.

On Rollers, 5 feet by 6 in size. New Edition. Price $5.

This popular work accomplishes for the first time, for Chemistry,
what maps and charts have for geography, geology, and astronomy, by
presenting a new and valuable mode of illustration. Its plan is to
represent chemical composition to the eye by colored diagrams, so that
numerous facts of proportion, structure, and relation, which are the
most difficult in the science, are presented to the mind through the
medium of the eye, and may thus be easily acquired and long retained.
The want of such a chart has long been felt by the thoughtful teacher,
and no other scientific publication that has ever emanated from
the American press has met with the universal favor that has been
accorded to this Chart. In the language of a distinguished chemist,
"Its appearance marks an era in the progress of the popularization of
Chemistry."

It illustrates the nature of elements, compounds, affinity, definite
and multiple proportions, acids, bases, salts, the salt-radical theory,
double decomposition, deoxidation, combustion and illumination,
isomerism, compound radicals, and the composition of the proximate
principles of food. It covers the whole field of Agricultural
Chemistry, and is invaluable as an aid to public lecturers, to teachers
in class-room recitation, and for reference in the family. The mode of
using it is explained in the class-book.

_From the late_ HORACE MANN, _President of Antioch College_.

  I think Mr. Youmans is entitled to great credit for the preparation
  of his Chart, because its use will not only facilitate acquisition,
  but, what is of far greater importance, will increase the exactness
  and precision of the student's elementary ideas.

_From_ DR. JOHN W. DRAPER, _Professor of Chemistry in the University of
N. Y._

  Mr. Youmans' Chart seems to me well adapted to communicate to
  beginners a knowledge of the definite combinations of chemical
  substances, and as a preliminary to the use of symbols, to aid
  them very much in the recollection of the examples it contains. It
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_From_ JAMES B. ROGERS, _Professor of Chemistry in the University of
Pennsylvania_.

  We cordially subscribe to the opinion of Professor Draper
  concerning the value to beginners of Mr. Youmans' Chemical Chart.

                  JOHN TORREY,
      _Professor of Chemistry in the College of Physicians &
          Surgeons, N. Y._

                 WM. H. ELLET,
      _Late Professor of Chemistry in Columbia College, S. C._

              JAMES B. ROGERS,
      _Professor of Chemistry in the University of Pennsylvania._

_From_ BENJAMIN SILLIMAN, LL. D., _Professor of Chemistry in Yale
College_.

  I have hastily examined Mr. Youmans' New Chemical Diagrams or Chart
  of chemical combinations by the union of the elements in atomic
  proportions. The design appears to be an excellent one.




History of Philosophy.


A History of Philosophy:

AN EPITOME.

BY DR. ALBERT SCHWEGLER.

TRANSLATED FROM THE ORIGINAL GERMAN, BY JULIUS H. SEELYE.

12mo. 365 pages. Price $1 25.

This translation is designed to supply a want long felt by both
teachers and students in our American colleges. We have valuable
histories of Philosophy in English, but no _manual_ on this subject so
clear, concise, and comprehensive as the one now presented. Schwegler's
work bears the marks of great learning, and is evidently written by
one who has not only studied the original sources for such a history,
but has thought out for himself the systems of which he treats. He has
thus seized upon the real germ of each system, and traced its process
of development with great clearness and accuracy. The whole history
of speculation, from Thales to the present time, is presented in its
consecutive order. This rich and important field of study, hitherto
so greatly neglected, will, it is hoped, receive a new impulse among
American students through Mr. Seelye's translation. It is a book,
moreover, invaluable for reference, and should be in the possession of
every public and private library.

_From_ L. P. HICKOK, _Vice-President of Union College_.

  "I have had opportunity to hear a large part of Rev. Mr. Seelye's
  translation of Schwegler's History of Philosophy read from
  manuscript, and I do not hesitate to say that it is a faithful,
  clear, and remarkably precise English rendering of this invaluable
  Epitome of the History of Philosophy. It is exceedingly desirable
  that it should be given to American students of philosophy in the
  English language, and I have no expectation of its more favorable
  and successful accomplishment than in this present attempt. I
  should immediately introduce it as a text-book in the graduate's
  department under my own instruction, if it be favorably published,
  and cannot doubt that other teachers will rejoice to avail
  themselves of the like assistance from it."

_From_ HENRY B. SMITH, _Professor of Christian Theology, Union
Theological Seminary, N. Y._

  "It will well reward diligent study, and is one of the best works
  for a text-book in our colleges upon this neglected branch of
  scientific investigation."

_From_ N. PORTER, _Professor of Intellectual Philosophy in Yale
College_.

  "It is the only book translated from the German which professes to
  give an account of the recent German systems which seems adapted to
  give any intelligible information on the subject to a novice."

_From_ GEO. P. FISHER, _Professor of Divinity in Yale College_.

  "It is really the best Epitome of the History of Philosophy now
  accessible to the English student."

_From_ JOSEPH HAVEN, _Professor of Mental Philosophy in Amherst
College_.

  "As a manual and brief summary of the whole range of speculative
  inquiry, I know of no work which strikes me more favorably."




Moral Philosophy.


Elements of Moral Philosophy:

ANALYTICAL, SYNTHETICAL, AND PRACTICAL.

BY HUBBARD WINSLOW.

12mo. 480 pages. Price $1 25.

This work is an original and thorough examination of the fundamental
laws of Moral Science, and of their relations to Christianity and to
practical life. It has already taken a firm stand among our highest
works of literature and science. From the numerous commendations of
it by our most learned and competent men, we have room for only the
following brief extracts:

_From the_ REV. THOMAS H. SKINNER, D. D., _of the Union Theol. Sem., N.
Y._

  "It is a work of uncommon merit, on a subject very difficult to be
  treated well. His analysis is complete. He has shunned no question
  which his purpose required him to answer, and he has met no
  adversary which he has not overcome."

_From_ REV. L. P. HICKOK, _Vice-President of Union College_.

  "I deem the book well adapted to the ends proposed in the preface.
  The style is clear, the thoughts perspicuous. I think it calculated
  to do good, to promote the truth, to diffuse light, and impart
  instruction to the community, in a department of study of the
  deepest interest to mankind."

_From_ REV. JAMES WALKER, D. D., _President of Harvard University_.

  "Having carefully examined the more critical parts, to which my
  attention has been especially directed, I am free to express my
  conviction of the great clearness, discrimination, and accuracy of
  the work, and of its admirable adaptation to its object."

_From_ REV. RAY PALMER, D. D., _of Albany_.

  "I have examined this work with great pleasure, and do not hesitate
  to say that in my judgment it is greatly superior to any treatise I
  have seen, in all the essential requisites of a good text-book."

_From_ PROF. ROUSSEAU D. HITCHCOCK, D. D., _of Union Theol. Sem., N. Y._

  "The task of mediating between science and the popular mind, is
  one that requires a peculiar gift of perspicuity, both in thought
  and style; and this, I think, the author possesses in an eminent
  degree. I am pleased with its comprehensiveness, its plainness, and
  its fidelity to the Christian stand-point."

_From_ PROF. HENRY B. SMITH, D. D., _of the Union Theol. Sem., N. Y._

  "It commends itself by its clear arrangement of the topics, its
  perspicuity of language, and its constant practical bearings. I am
  particularly pleased with its views of conscience. Its frequent
  and pertinent illustrations, and the Scriptural character of its
  explanations of the particular duties, will make the work both
  attractive and valuable as a text-book, in imparting instruction
  upon this vital part of philosophy."

_From_ W. D. WILSON, D. D., _Professor of Intellectual and Moral
Philosophy in Hobart Free College_.

  "I have examined the work with care, and have adopted it as
  a text-book in the study of Moral Science. I consider it not
  only sound in doctrine, but clear and systematic in method, and
  withal pervaded with a prevailing healthy tone of sentiment,
  which cannot fail to leave behind, in addition to the truths it
  inculcates, an impression in favor of those truths. I esteem this
  one of the greatest merits of the book. In this respect it has
  no equal, so far as I know; and I do not hesitate to speak of it
  as being preferable to any other work yet published, for use in
  all institutions where Moral Philosophy forms a department in the
  course of instruction."




Transcribers' Notes:


Punctuation and spelling were made consistent when a predominant
preference was found in this book; otherwise they were not changed.

Simple typographical errors were corrected; occasional unbalanced
quotation marks retained.

Ambiguous hyphens at the ends of lines were retained.

This text spells "gauge" as "guage" in all but one instance; none
changed here.

Page 34: "by a break put on" perhaps should be "brake".

Page 40: "conveyed upwards fourteen" probably should be "conveyed
upwards of fourteen".

Page 70: "the prepare surfaced" probably is a misprint for "surface".

Page 83: "re-agents" was printed that way.

Page 197: "distil" was printed that way.

Page 208: "metropolitian" was printed that way.