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SCIENTIFIC AMERICAN SUPPLEMENT NO. 1082




NEW YORK, SEPTEMBER 26, 1896.

Scientific American, established 1845.

Scientific American Supplement. Vol. XLII., No. 1082.

Scientific American Supplement, $5 a year.

Scientific American and Supplement, $7 a year.

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TABLE OF CONTENTS.

                                                                PAGE
I.    ARCHITECTURE.--New Methods of Building Construction at
      Paris.--A typical French system of
      construction.--Combination of plaster and iron; cement
      armé.--1 illustration.                                    17292

II.   AUTOCARS.--The De Dion and Bouton Road Motor.--An
      elaborate description of this typical French motor
      operated by steam.--4 illustrations.                      17290

III.  CHEMISTRY.--An Air Bath.--By B.J.H. COSTE.--1
      illustration.                                             17296

      The Feculometer.--1 illustration.                         17295

IV.   DOMESTIC ECONOMY.--Errors in Our Food Economy.--A very
      practical paper on scientific nutrition.                  17288

V.    GEOGRAPHY.--Zanzibar.--An account of the country and the
      recent events there.--3 illustrations.                    17287

VI.   MATHEMATICS.--Goodman's Hatchet Planimeters.--Instrument
      for measuring areas and mean altitudes or irregular
      figures.--5 illustrations.                                17293

VII.  METALLURGY.--The Great Krupp Works.--Notes on the great
      iron and steel works of the German empire, with
      statistics.                                               17302

VIII. MINERALOGY.--Precious Stoned--By Prof. HENRY A.
      MIERS.--Lecture I.--First installment of a most
      interesting article on the minerals used in the jeweler's
      art.--3 illustrations.                                    17298

IX.   MINING ENGINEERING.--Firedamp Testing Station at
      Marchienne-au-Pont.--An elaborate experimental station
      for investigation into firedamp.--3 illustrations.        17297

X.    MISCELLANEOUS.--Device for the Display of Lantern
      Slides.--An apparatus for the display of lantern slides
      in the shop window.--A rotating carrier.--2
      illustrations.                                            17295

      What the Sea Has Taken.--Destruction of great areas of
      country in the past, with special reference to the Dutch
      coast.                                                    17289

      Engineering Notes.                                        17301

      Electrical Notes.                                         17301

      Miscellaneous Notes.                                      17301

      Selected Formulæ.                                         17302

XI.   NATURAL HISTORY.--Some Notes on Spiders.--By Rev. SAMUEL
      BARBER.--Some very curious observations on arachnids.     17300

XII.  NAVIGATION.--From New York to Havre in a Rowboat.--The
      most wonderful trip on record across the ocean, with
      portraits of the navigators and view of the boat.--2
      illustrations.                                            17291

      The Waste of Shipping:--Losses of steam and sailing
      vessels due to wreckage and condemnation, with valuable
      tables.                                                   17291

XIII. OPTICS.--The Colors Named in Literature.--With table.     17289

XIV.  PHOTOGRAPHY.--Photography for Chemists.--Lantern slides
      by reduction.--How to produce lantern slides from large
      negatives.                                                17297

XV.   PHYSICS.--A Research on the Liquefaction of Helium.--A
      research in advanced experimental physics upon the newly
      discovered element helium.--1 illustration.               17299

      Physics Without Apparatus.--Several interesting and
      simple experiments described.--1 illustration.            17302

XVI.  TECHNOLOGY.--Apparatus for the Manufacture of Acetylene
      Gas.--Description of a number of prominent acetylene
      apparatus, with illustrations and sectional views
      thereof.--12 illustrations.                               17294

      Belleek China.--History of this beautiful china, and
      foundation of its manufacture in Ireland and subsequent
      introduction into America.--Description of different
      Belleek marks.                                            17292

      The Coming Light.--An incandescent gas burner employing
      artificial draught produced by electric motor.--2
      illustrations.                                            17296

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ZANZIBAR.


The sudden death on August 25 of Sultan Hamid bin Thwain, the ruler of
Zanzibar, the attempted usurpation by Seyyid Khalid, and the
bombardment of the palace by the British warships, have directed
public attention to this comparatively little known but important city
on the east coast of Africa.

The Zanzibar dominions achieved their independence some forty years
ago under Seyyid Majid, whose father was Seyyid Said, the Sultan of
Muscat and Zanzibar. The dominions formerly extended from Warsheik
south to Tanghi Bay. In 1890 the coast line from Ruvuma to Wanga, with
the island of Mafia, was ceded to Germany, by which partition the
country was reduced to two islands, Zanzibar and Pemba, containing
about a thousand square miles with 165,000 inhabitants, a strip of
coast line ten miles long, together with three smaller islands and
five seaports. Zanzibar is a British protectorate, as are also the
Zanzibar dominions on the mainland as far north as the mouth of the
Juba. The remainder of the mainland dominions to the south are leased
to an Italian company.

[Illustration: PALACE SQUARE, ZANZIBAR: TROOPS ASSEMBLED IN FRONT OF
GOVERNMENT HOUSE; PALACE, WITH THE LATE SULTAN IN THE GALLERY, TO THE
RIGHT HAND; HAREM TO THE LEFT.]

The island of Zanzibar, together with the neighboring islands of Pemba
and Mafia, to the north and south, is generally of coral formation,
with here and there hills of a reddish clay, which rise in the south
to an elevation of 450 feet and in the north develop into a range of
hills which runs parallel to the shore at a height of over 1,000 feet.
The dense forests which originally covered the island have been cut
down, and the soil, which is of unusual fertility, is under thorough
cultivation, yielding heavy crops of corn and manioc, which latter
forms the staple food of the people.

The soil and climate are specially suited to the clove, which is
raised in great quantities, the crop forming four-fifths of the total
clove crop of the world. The seaboard lying opposite the island of
Zanzibar is level and swampy, and the many rivers which flow from the
escarpment of the great inland plateau have brought down a vast
deposit of rich alluvial matter, upon which, aided by the moist, warm
climate, a dense growth of tropical vegetation flourishes. A native
growth of this region is the copal tree, famous as yielding the best
gum known to commerce. Rice, maize, millet, the cocoa nut and the oil
palm are cultivated, and the whole country is well adapted to the
raising of sugar, coffee, cotton, indigo, and the various spices.

Of the original races of the island of Zanzibar only a few
representatives survive. These live on the east side, and are known as
Wa-Hadimu Bantus. The main population is a strange mixture of "full
blood and half-caste Arabs, Indian 'Canarians' (that is, half-caste
Portuguese from Kanara on the Malabar coast of India), Swahili of
every shade, slaves or freedmen from all parts of East Africa," with a
small sprinkling of Americans and Europeans.

The city of Zanzibar is, next to Alexandria and Tunis, the largest
city on the coast of Africa, and contains a population variously
estimated at from 80,000 to 100,000 souls. It is easily separable into
two quarters, the trading quarter, which lies along the beach and
contains the palace of the Sultan, and the eastern outlying suburb in
which live the lower class. The view of Zanzibar from the sea is
picturesque, the palace, forts and towers, the Mission Cathedral and
the successive white buildings of varied outline, making a pleasing
panorama. But when the visitor passes into the heart of the city he
loses himself in a tangle of foul and narrow streets, where filth and
immorality abound.

[Illustration: THE LATE SULTAN OF ZANZIBAR AND HIS MINISTERS.]

The palace, which is the central point of the city's life, is thus
described by a former resident, Mr. Charles L. Lyons: "A low, rambling
structure divided into three parts. The higher portion is of stone,
and surrounded by verandas of carved teak wood, which are very ornate
and elaborate specimens of eastern decorative art work. Adjoining this
is the section occupied as living apartments, and the third section is
occupied by the harem, which, under the late Sultan, comprised about
twenty-five Circassian women.

"The palace was a curious combination of magnificence and tawdriness.
The reception room, which is about 250 ft. square, was hung with
beautiful draperies embroidered in real gold. In many places the walls
were inlaid with precious stones curiously and indiscriminately
mingled. Next to a valuable uncut sapphire or a ruby one would find a
carbuncle or some valueless stone. Many of the chairs in the finer
apartments were of gold inlaid with precious stones, and about many of
the rooms were inscriptions from the Koran applied in solid gold."
Other conspicuous buildings as seen from the water are the Government
House, the Custom House, the Signal Tower, and the Mission Cathedral.

[Illustration: EXTERIOR VIEW OF THE SULTAN'S PALACE, ZANZIBAR.]

The harbor affords a fine anchorage for shipping, and is well worthy
to be the central shipping point of the east coast of Africa. The
total imports for 1894 were valued at over $6,000,000 and the exports
at about $5,500,000. British India controls the greater share of the
import trade, sending over large cargoes of grain, rice, and piece
goods from Bombay, the yearly value of the trade being $1,675,000. The
German trade amounts to $340,000, and a large amount of cotton goods
and kerosene oil is imported from America.

The law of succession to the throne of Zanzibar does not recognize the
right of the eldest son or the son of the eldest brother deceased. In
the eyes of the Mohammedan Council of State Seyyid Khalid, the late
usurper, has no stronger claim to the throne than his cousin, the
present Sultan Hamid bin Mohammed bin Seyyid. Khalid is spoken of as
"a rash and willful young man of twenty-five," and Hamid as "an
elderly gentleman, fifty or sixty years of age, respected for his
prudent and peaceable conduct, acceptable to the better class of
Mussulman townsfolk, and trusted as a ruler likely to preserve the
traditional policy of the realm." Immediately upon the interment of
the late Sultan, however, which took place two short hours after his
suspicious death, Khalid proclaimed himself ruler. He gathered the
palace guards together, placed barricades in the palace square,
trained the guns upon the British warships, and awaited developments.
They came the next morning in the shape of an ultimatum from Admiral
Rawson of the St. George, a first class cruiser of 7,700 tons, which,
together with four smaller cruisers and gunboats, lay off the city in
the harbor, summoning Khalid to surrender, leave the palace, and make
his soldiers pile their arms in front of it. If he failed to do this,
the palace would be bombarded within two hours after the dispatch of
the ultimatum.

As Khalid's reply was to further strengthen his defense, at the
appointed time the bombardment began. Meanwhile the loyal Zanzibar
troops, with a detachment of British marines and seamen, attacked the
barricades. The palace was knocked to pieces and set on fire by the
shells, and Khalid, driven from the shelter, fled to the German
consulate for safety.

Hamid was proclaimed Sultan by General Matthews, Mr. Cave, the consul,
and Admiral Rawson, and order was at once restored to the city.

At the time of the bombardment it was freely predicted that the
annexation of Zanzibar would speedily follow; but it now appears that
the government considers that no advantages are to be gained by such a
step, the cost of a direct administration being much greater than the
native administration, which under the present protectorate is working
satisfactorily.

We are indebted for our illustrations to the Illustrated London News
and to Black and White.

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ERRORS IN OUR FOOD ECONOMY.


Scientific research, interpreting the observations of practical life,
implies that several errors are common in the use of food.

First, many people purchase needlessly expensive kinds of food, doing
this under the false impression that there is some peculiar virtue in
the costlier materials, and that economy in our diet is somehow
detrimental to our dignity or our welfare. And, unfortunately, those
who are most extravagant in this respect are often the ones who can
least afford it.

Secondly, the food which we eat does not always contain the proper
proportions of the different kinds of nutritive ingredients. We
consume relatively too much of the fuel ingredients of food, such as
the fats of meat and butter, the starch which makes up the larger part
of the nutritive material of flour and potatoes and sugar and
sweetmeats. Conversely, we have relatively too little of the protein
of flesh-forming substances, like the lean of meat and fish and the
gluten of wheat, which make muscle and sinew and which are the basis
of blood, bone and brain.

Thirdly, many people, not only the well-to-do, but those in moderate
circumstances, use needless quantities of food. Part of the excess,
however, is simply thrown away with the wastes of the table and the
kitchen; so that the injury to health, great as it may be, is
doubtless much less than if all were eaten. Probably the worst
sufferers from this evil are well-to-do people of sedentary
occupations--brain workers as distinguished from hand workers.

Finally, we are guilty of serious errors in our cooking. We waste a
great deal of fuel in the preparation of our food, and even then a
great deal of the food is very badly cooked. A reform in these methods
of cooking is one of the economic demands of our time.

Cheap vs. Dear Food.--We cannot judge of the nutritive value of food
by the quantity. There is as much nutriment in a pound of wheat flour
as in 3½ quarts of oysters, which weigh 7 pounds. There is still less
connection between nutritive value and price. In buying at ordinary
market rates we get as much material to build up our bodies, repair
their wastes, and give strength for work in 5 cents' worth of flour or
beans or codfish as 50 cents or $1 will pay for in tenderloin, salmon
or lobsters.

Round steak at 15 cents a pound is just as digestible and is fully as
nutritious as tenderloin at 50. Mackerel has as high nutritive value
as salmon, and costs from an eighth to half as much. Oysters are a
delicacy. If one can afford them, there is no reason for not having
them, but 25 cents invested in a pint would bring only about an ounce
of protein and 230 calories of energy. The same 25 cents spent for
flour at $6 a barrel, or 3 cents a pound, would pay for nine-tenths of
a pound of protein and 13,700 calories of energy. When a day laborer
buys bread at 7½ cents a pound, the actual nutritive material costs
him three times as much as it does his employer, who buys it in flour
at $6 a barrel.

Illustrations of the prejudice of people, especially those in moderate
circumstances, against the less expensive kinds of food are very
common.

Mr. Lee Meriwether, who has given much attention to this special
subject, cites a case in point, that of a coal laborer, who boasted:
"No one can say that I do not give my family the best flour, the
finest of sugar, the very best quality of meat." He paid $156 a year
for the nicest cuts of meat, which his wife had to cook before six in
the morning or after half past six at night, because she worked all
day in a factory. When excellent butter was selling at 25 cents a
pound he paid 29 cents for an extra quality. He spent only $108 a year
for clothing for his family of nine, and only $72 a year for rent in a
close tenement house, where they slept in rooms without windows or
closets. He indulged in this extravagance in diet, when much less
expensive food materials, such as regularly come upon the tables of
men of wealth, would have been just as nutritious, just as wholesome,
and in every way just as good, save in the gratification to pride and
palate. He was committing an immense economic blunder. Like thousands
of others, he did so in the belief that it was wise and economical.

The sad side of the story is that the poor are the ones who practice
the worst economy in the purchase as well as the use of food. The
Massachusetts Bureau of Labor, in collecting the dietaries above
referred to, made numerous inquiries of tradesmen regarding the food
of the poor in Boston, meaning by poor "those who earn just enough to
keep themselves and families from want." The almost universal
testimony was, "They usually want the best and pay for it, and the
most fastidious are those who can least afford it." The costliest kind
of meat, the finest flour, and very highest priced butter were
demanded, and many scorned the less expensive meats and groceries such
as well-to-do and sensible people were in the habit of buying.

I have taken occasion to verify these observations by personal inquiry
in Boston markets. One intelligent meat man gave his experience with a
poor seamstress, who insisted on buying tenderloin steak at 60 cents
per pound. He tried to persuade her that other parts of the meat were
just as nutritive, as they really are, but she would not believe him;
and when he urged the wiser economy of using them, she became angry at
him for what she regarded as a reflection upon her dignity. "My
wealthy customers," said he, "take our cheaper cuts, but I have got
through trying to sell these economical meats to that woman and others
of her class."

I am told that people in the poorer parts of New York City buy the
highest priced groceries, and that the meat men say they can sell the
coarser cuts of meat to the rich, but that people of moderate means
refuse them. I hear the same thing in Washington and other cities.

One-sidedness of Our Dietary.--I have said that our diet is
one-sided, that the food which we actually eat has relatively too
little protein and too much fat, starch, and sugar. In other words, it
is relatively deficient in the materials which make muscle and bone
and contains a relative excess of the fuel ingredients. This is due
partly to our large consumption of sugar and partly to our use of such
large quantities of fat meats.

Overeating--Injury to Health.--But the most remarkable thing about our
food consumption is the quantity. The American dietaries examined in
this inquiry were of people living at the time in Massachusetts and
Connecticut, though many came from other parts of the country. It
would be wrong to take their eating habits as an exact measure of
those of people throughout the United States. For that matter, a great
deal of careful observation will be needed to show precisely what and
how much is used by persons of different classes in different regions.
Just this kind of study in different parts of the country is greatly
needed. But such facts as I have been able to gather seem to imply
that the figures obtained indicate in a general way the character of
our food consumption. Of the over 50 dietaries of reasonably
well-to-do people thus far examined the smallest is that of a
mechanic's family. In this the potential energy per man per day was
about 3,000 calories. The next smallest was that of the family of a
chemist who had been studying the subject and had learned something of
the excessive amounts of food which many people with light muscular
labor consume. This dietary supplied 3,200 calories of energy per man
a day. The largest was that of brickmakers at very severe work in
Massachusetts. They lived in a boarding house managed by their
employers, who had evidently found that men at hard muscular work out
of doors needed ample nourishment to do the largest amount of work.
The food supplied 8,850 calories per day.

Voit's standard for a laboring man at moderate work, which is based
upon the observation of the food of wage workers, who are counted in
Germany as well paid and well fed, allows 118 grammes of protein and
3,055 calories of energy. The standards proposed by myself, in which
the studies of American dietaries have been taken into account, allow
125 grammes of protein and 3,500 calories of energy for a man at
moderately hard muscular work. The dietaries of Massachusetts and
Connecticut factory operatives, day laborers and mechanics at moderate
work averaged about 125 grammes of protein and 4,500 calories of
energy. For a man at "severe" work, Voit's standard calls for 145
grammes of protein and 3,370 calories of energy.

The Massachusetts and Connecticut mechanics at "hard" and "severe"
work had from 180 to 520 grammes of protein and from 5,000 to 7,800
calories of potential energy, and in one case they rose to the 8,500
just quoted. In the dietary standards proposed by myself it did not
seem to me permissible to assign less than 4,000 calories to that for
a working man at "hard," and 5,700 for a man at "severe" work.[1]

    [Footnote 1: Statistics are also given showing that the
    professional men of certain European countries live comfortably
    and have good health on much less than Americans of the same
    occupation.--ED.]

Now it is not easy to see why these men required so much more than was
sufficient to nourish abundantly men of like occupation, but unlike
temptation to overeating, in Europe. Difference in climate cannot
account for it. We are a little more given to muscular exercise here,
which is very well for us, but it cannot justify our eating so
much.... I think the answer to this question is found in the
conditions in which we live. Food is plenty. Holding to a tradition
which had its origin where food was less abundant, that the natural
instinct is the measure of what we should eat, we follow the dictates
of the palate. Living in the midst of abundance, our diet has not been
regulated by the restraints which obtain with the great majority of
the people of the Old World, where food is dear and incomes are small.

Indeed, the very progress which we are making in our civilization
brings with it increased temptation to overeating. The four quarters
of the earth are ransacked to supply us with the things which will
most tempt our appetites, and the utmost effort of cooks and
housewives is used in the same direction. It is all the more fitting,
therefore, that information as to our excesses and the ways of
avoiding them should come at the same time.

How much harm is done to health by our one-sided and excessive diet no
one can say. Physicians tell us that it is very great. Of the vice of
overeating, Sir Henry Thompson, a noted English physician and
authority on the subject, says:

"I have come to the conclusion that more than half the disease which
embitters the middle and latter part of life is due to avoidable
errors in diet, ... and that more mischief in the form of actual
disease, of impaired vigor, and of shortened life accrues to civilized
man ... in England and throughout central Europe from erroneous habits
of eating than from the habitual use of alcoholic drink, considerable
as I know that evil to be."

This is in the fullest accord with the opinions of physicians and
hygienists who have given the most attention to the subject, and these
opinions are exactly parallel with the statistics here cited.

Waste of Food in American Households.--The direct waste of food occurs
in two ways, in eating more than is needed and in throwing away
valuable material in the form of kitchen and table refuse. That which
is thrown away does no harm to health, and in so far as part of it may
be fed to animals or otherwise utilized, it is not an absolute loss.
That which we consume in excess of our need of nourishment is worse
than wasted, because of the injury it does to health. A few instances
taken from the investigations mentioned above will help to illustrate
the waste of food.

One of the dietaries examined by the Massachusetts Labor Bureau was
that of a machinist in Boston, who earned $3.25 per day. In food
purchased the dietary furnished 182 grammes of protein and 5,640
calories of energy per man per day, at a cost of 47 cents. One-half
the meats, fish, lard, milk, butter, cheese, eggs, sugar, and molasses
would have been represented by 57 grammes of protein, 1,650 calories,
and 19 cents. If these had been subtracted, the record would have
stood at 125 grammes, 3,990 calories, and 28 cents. This family might
have dispensed with one-half of all their meats, fish, eggs, dairy
products, and sugar, saved 40 per cent. of the whole cost of their
food, and still have had all the protein and much more energy than is
called for by a standard which is supposed to be decidedly liberal.

In the instance just cited no attempt was made to learn how much of
the food purchased was actually consumed and how much was rejected. In
some of the dietaries published by the Massachusetts bureau such
estimates were made. That of a students' club in a New England college
will serve as an example.

The young men of the club, some 25 in number, were mostly from the
Northern and Eastern States, and coming from the class of families
whose sons go to college, it seems fair to assume that their habits of
eating formed at home would not differ materially from those of the
more intelligent classes of people in that part of the country. While
the diet of the club was substantial and wholesome, it was plain, as
was, indeed, necessary, because several of the members were dependent
upon their own exertions and the majority had rather limited means.
Though fond of athletic sports they could hardly be credited with as
much muscular exercise as the average "laboring man at moderate work."
The matron, a very intelligent, capable New England woman, had been
selected because of her especial fitness for the care of such an
establishment. The steward who purchased the food was a member of the
club, and had been chosen as a man of business capacity. He thought
that very little of the food was left unconsumed. "All of the meat and
other available food that was not actually served to the men at the
table," said he, "was carefully saved and made over into croquettes.
Men who work their way through college cannot afford to throw away
their food." But actual examination showed the waste to be
considerable. The estimates of the quantities of nutrients were based
upon the quantities of food materials for a term of three months and
upon the table and kitchen refuse for a week. The results were as
follows: In food purchased, protein, 161 grammes; energy, 5,345
calories. In waste, protein, 23 grammes; energy, 520 calories. In food
consumed, protein, 138 grammes; energy, 4,825 calories. One-eighth of
the protein and one-tenth of the energy were simply thrown away.

During the succeeding term a second examination of the dietary of the
same club was made. Another steward was then in charge. He had learned
of the excessive amounts of food in the former dietary, and planned to
reduce the quantities. This was done largely by diminishing the meats.
He stated that he did not apprise the club of the change, and that it
was not noticed. As he put it, "The boys had all they wanted, and were
just as well pleased as if they had more." Estimates as before but
with more care in determining the waste, showed in food purchased,
protein, 115 grammes; energy, 3,875 calories. In waste, protein, 11
grammes; energy, 460 calories. In food consumed, protein, 104 grammes;
energy, 3,415 calories. One-tenth of the nutritive material of the
food this time was thrown away. The young men were amply nourished
with three-fifths of the nutrients they had purchased in the previous
term.

How much food is required on the average by men whose labor is mainly
intellectual is a question to which physiology has not yet given a
definite answer, but it is safe to say that the general teaching of
the specialists who have given the most attention to the subject would
call for little more than the 104 grammes of protein and very much
less than the 3,400 calories of energy in the food estimated to be
actually consumed by these young men when the second examination was
made. They could have dispensed with half of all the meats, fish,
oysters, eggs, milk, butter, cheese, and sugar purchased for the first
dietary and still have had more nutritive material than they consumed
in the second. Not only was one-tenth or more of the nutrients thrown
away in each of the two cases, but what makes the case still worse
pecuniarily, the rejected material was very largely from the animal
foods in which it is the most expensive.

The estimates of the quantities of food in the two dietaries just
quoted were made from tradesmen's bills and the composition was
calculated from analyses of similar materials rather than of those
actually used. The figures are therefore less reliable than if the
foods and wastes had been actually weighed and analyzed. In some
dietaries lately examined in Middletown, Conn., all the food has been
carefully weighed and portions have been analyzed, and the same has
been done with the table and kitchen refuse. The results, therefore,
show exactly how much was purchased, consumed and thrown away. One
dietary so investigated was that of a boarding house. The boarders
were largely mechanics of superior intelligence and skill, and earning
good wages; the mistress was counted an excellent housekeeper and the
boarding house a very good one. About one-ninth of the total nutritive
ingredients of the food was left in the kitchen and table refuse. The
actual waste was worse than this proportion would imply, because it
consisted mostly of the protein and fats, which are more costly than
the carbohydrates. The waste contained nearly one-fifth of the total
protein and fat, and only one-twentieth of the total carbohydrates of
the food. Or to put it in another way, the food purchased contained
about 23 per cent. more protein, 24 per cent. more fats, and 6 per
cent. more carbohydrates than were eaten. And worst of all for the
pecuniary economy, or lack of economy, the wasted protein and fats
were mostly from the meats which supply them in the costliest form.

In another dietary, that of a carpenter's family, also in Middletown
Conn., 7.6 per cent. of the total food purchased was left in the
kitchen and table wastes. The total waste was somewhat worse than this
proportion would imply, because it consisted mostly of the protein and
fats, which are more costly than the carbohydrates. The waste
contained about one-tenth of the total protein and fat and only
one-twenty-fifth of the total carbohydrates of the food. At the rate
in which the nutrients were actually eaten in this dietary, the
protein and fats in the waste would have each supplied one man for a
week and the carbohydrates for three days.

These cases are probably exceptional; at least it is to be hoped that
they are. Among eight dietaries lately studied in Middletown those
above named showed the largest proportion of material thrown away. In
the rest it was much less. In two cases there was almost none. It is
worth noting, however, that the people in these two had the largest
incomes of all. In other words the best-to-do families were the least
wasteful.

This form of bad economy is not confined to the kitchen, but begins in
the market.... The common saying that "the average American family
wastes as much food as a French family would live upon" is a great
exaggeration, but the statistics cited show that there is a great deal
of truth in it. Even in some of the most economical families the
amount of food wasted, if it could be collected for a month or a year,
would prove to be very large, and in many cases the amounts would be
little less than enormous.--W.O. Atwater, Charities Review.

       *       *       *       *       *




THE COLORS NAMED IN LITERATURE.


Mr. Havelock Ellis has made (Contemporary Review, May) an interesting
study of the color terms used by imaginative writers, which is a real
contribution to scientific æsthetics. The fact that the Greeks did not
name green and blue does not, of course, indicate (as Mr. Gladstone
and others have alleged) that they could not see the more refrangible
rays of the spectrum, but it does show a lack of interest in these
colors. Mr. Ellis' statistics are given in the annexed table, the
number of times each of the colors is used by the author in selected
passages being reduced to percentages.

------------------+------+-------+----+------+-----+------+--------------------+
                  |White.|Yellow.|Red.|Green.|Blue.|Black.|    PREDOMINANT     |
------------------+------+-------+----+------+-----+------+--------------------+
Mountain of Chant |  28  |   13  |  3 |  ... |  19 |  37  |Black, white.       |
Wooing of Emer    |  34  |    3  | 48 |  ... | ... |  14  |Red, white.         |
Volsunga Saga     |  14  |  ...  | 71 |  ... |  14 | ...  |Red.                |
Isaiah, Job,      |      |       |    |      |     |      |                    |
   Song of Songs  |  18  |    4  | 29 |   33 | ... |  15  |Green, red.         |
Homer             |  21  |   21  |  7 |    2 | ... |  49  |Black, white-yellow.|
Catullus          |  40  |   21  | 17 |    9 |   4 |   8  |White, yellow.      |
Chaucer           |  34  |   10  | 28 |   14 |   1 |  13  |White, red.         |
Marlowe           |  19  |   21  | 19 |    6 |   6 |  28  |Black, yellow.      |
Shakespeare       |  22  |   17  | 30 |    7 |   4 |  20  |Red, white.         |
Thomson           |   9  |  ...  | 18 |   27 |   9 |  36  |Black, green.       |
Blake             |  17  |   17  | 13 |   16 |   7 |  29  |Black, white-yellow.|
Coleridge         |  21  |    7  | 17 |   25 |  14 |  16  |Green, white.       |
Shelley           |  17  |   19  | 11 |   21 |  21 |  11  |Green-blue.         |
Keats             |  14  |   23  | 24 |   29 |   8 |   1  |Green, red.         |
Wordsworth        |  14  |   18  | 10 |   35 |  11 |  12  |Green, yellow.      |
Poe               |   8  |   32  | 20 |   12 |   4 |  24  |Yellow, black.      |
Baudelaire        |  11  |    9  | 19 |   10 |  16 |  34  |Black, red.         |
Tennyson          |  22  |   15  | 27 |   15 |  10 |  11  |Red, white.         |
Rossetti          |  30  |   22  | 22 |    9 |   7 |  10  |White, yellow.      |
Swinburne         |  28  |   18  | 28 |   16 |   6 |   4  |Red, white.         |
Whitman           |  25  |   10  | 26 |   14 |   8 |  16  |Red, white.         |
Pater             |  43  |   19  | 11 |   11 |   9 |   7  |White, yellow.      |
Verlaine          |  20  |   15  | 24 |    9 |  14 |  18  |Red, white.         |
Olive Schreiner   |  38  |   12  | 25 |    3 |  19 |   2  |White, red.         |
D'Annunzio        |  15  |   11  | 46 |    7 |  14 |   6  |Red, white.         |
------------------+------+-------+----+------+-----+------+--------------------+

Mr. Ellis makes a number of acute psychological and literary
suggestions and concludes that a numerical study of color vision
"possesses at least two uses in the precise study of literature. It
is, first, an instrument for investigating a writer's personal
psychology, by defining the nature of his æsthetic color vision. When
we have ascertained a writer's color formula and his colors of
prediction we can tell at a glance, simply and reliably, something
about his view of the world which pages of description could only tell
us with uncertainty. In the second place, it enables us to take a
definite step in the attainment of a scientific æsthetic, by
furnishing a means of comparative study. By its help we can trace the
colors of the world as mirrored in literature from age to age, from
country to country, and in finer shades among the writers of a single
group. At least one broad and unexpected conclusion may be gathered
from the tables here presented. Many foolish things have been written
about the 'degeneration' of latter-day art. It is easier to dogmatize
when you think that you are safe from the evidence of precise tests.
But here is a reasonably precise test. And the evidence of this test,
at all events, by no means furnishes support for the theory of
decadence. On the contrary, it shows that the decadence, if anywhere,
was at the end of the last century, and that our own vision of the
world is fairly one with that of classic times, with Chaucer's and
with Shakespeare's. At the end of the nineteenth century we can say
this for the first time since Shakespeare died."--Science.

       *       *       *       *       *




WHAT THE SEA HAS TAKEN.


It was recently announced that the committee sitting under the
presidency of Minister Lely, at the Hague, had determined to reclaim
the Zuider Sea, and that for this purpose a dam is to be constructed
from the peninsula of North Holland to the opposite coast of
Friesland.

This announcement brings back to recollection the proud old Dutch
proverb: "God created the sea, the Hollander the coast."

The proposal is to construct a dam from Ewyk, on the northeastern
point of North Holland, to the island of Wieringen, and then from the
eastern point of this island another dam, 18½ miles long, to the coast
of Friesland, by the shortest route.

The Hollanders, in their great reclamation works, the Sea of Harlem,
for instance, prepare the entire foundation first and then gradually
raise the dam on it. The watercourse is not narrowed during the
progress of the work, as the dam is raised uniformly throughout the
whole length; the current therefore passes slowly over it, and the dam
is not subject to damage from flood waters. These deposit enormous
quantities of sand and mud within the intercepted area, and after a
few years the land shows above the surface of the water; the land
while still in course of formation is locally known as "Heller," and
the reclaimed land as "Polder."

As soon as the land has attained the required height, the dam is built
sufficiently high, and also strong enough, to answer the purposes of a
dike and to withstand the force of the largest tidal waves.

In constructing these dams, enormous rafts are made on the shore and
then floated to the works, where they are weighted by stones and sunk
in the required position. Within a few weeks large quantities of silt
and mud accumulate, and the whole forms an exceedingly tough and
strong elevation under the water; the currents grow weaker, and
deposits are lodged also outside the dam, the base of which is of
course of great width.

The Zuider Sea is one of the strongest evidences we have of the power
of the sea over the land. Its formation commenced as far back as the
twelfth century, prior to which it was only an inland lake. On
December 14, 1287, during a terrific storm, the sea broke through the
dividing shore line and widened the lake into a wide bay (Southern
Sea, Dutch, Zuider Sea) of the North Sea; 80,000 persons lost their
lives on that occasion. The same storm also did enormous damages in
other localities.

This was, however, not the first occasion on which the sea had made
inroads into the coast lands. Before the works of destruction
commenced a narrow isthmus connected Great Britain with the Continent.
The North Sea was then--comparatively speaking--calm; vast chains of
sandy downs ran parallel to the coast, and stretched from this isthmus
to the coast of Jutland; they were of considerable height, those on
the west coast of Schleswig attaining an altitude of 200 feet. Behind
these downs enormous swamps are formed, in which the rivers, with few
exceptions, disappeared; but the deposits they brought down formed
those rich agricultural lands now known locally as "Marschland."

The destruction of the shores commenced from the date that the narrow
isthmus above referred to was carried away by the tidal waves which
broke the English Channel during westerly gales. Traces, found far
inland, show that this catastrophe occurred when the locality was
inhabited, in fact a legend, in circulation to this day, relates that
an English queen, to revenge herself on a Danish king, had the dam
which connected England with France pierced, and so destroyed Denmark.
When the Romans appeared on the scene the work of destruction was in
progress, the chain of downs had been broken, and its place taken by
many islands, far larger and more numerous than at present.

The first historical accounts of the storm tidal waves is referred to
by Strabo as having occurred in 113 B.C., this, he relates, drove the
Cimbers and Teutons from their homes and was the cause of their
threatening Rome. Many other floods occurred which are known as
"Manntranke" (man drowning). In the flood of 1216, for instance,
10,000 persons lost their lives, and three years later the
"Marcellus" flood caused similar destruction. In 1300 the second
"Marcellus" flood broke 12 feet over the highest dikes and Schleswig
alone lost 7,600 persons in the waves.

Heligoland was at that time a large island, 46 miles long and 24 miles
wide, it contained a monastery, many churches, large villages,
extensive cultivations and forests; the island was all but destroyed
by this inundation. Before that disastrous occurrence the island could
be seen from the shores of Friesland, which in the days of Charles the
Great was twice as large as now. The Friesland of to-day is only the
southern and poorest remnant of the magnificent lands which were
completely destroyed on October 11, 1684; 20 parishes and 150,000
persons disappeared beneath the waves, which broke through the dikes
simultaneously in twenty-four places.

To relate all inundations would lead too far, but the most serious may
be mentioned as showing the struggles in which the inhabitants of the
North Sea coast are engaged. That of 1421, which swallowed 21 parishes
and 100,000 persons; then the most terrible of which there is any
record, and which is known as the "All Saints' Day" flood of 1570; the
sea raged along the whole of the coast from Holland to Jutland for
forty-eight hours, carried away all the dikes and caused the loss of
400,000 lives; the whole country lay waste for years, for the want of
population to rebuild the dikes.

The Christmas flood of 1717 also visited the whole coast and 15,000
lives were lost.

During the present century the destruction by the sea has been
minimized, as the dikes are now built strong and high enough to
withstand the heaviest seas. The various islands along the coast act
as breakwaters and protect, to a great extent, the coast line; the
various governments are endeavoring to strengthen the islands by
vegetation, but it appears to be only a question of time when they
will disappear altogether.

Although the sea has, during the past 1,000 years, robbed the Dutch of
great tracts of land, yet they have, by enduring perseverance,
recovered a great deal, and there appears no doubt that they will
succeed to form the Zuider Sea into rich agricultural lands, just as
they have already dried up the Harlem Sea and converted it into waving
cornfields.

Ground is also gained yearly in other directions, by continually
extending the dikes; the richest lands on the coasts of Holland and
Germany have thus been reclaimed from the ocean, and they are
protected by means which secure the coasts against future
encroachment.

       *       *       *       *       *

[Continued from SUPPLEMENT, No. 1080, page 17263.]




THE DE DION AND BOUTON ROAD MOTOR.


It was with a vehicle of the kind described in our last article that
Messrs. De Dion and Bouton obtained a conspicuous success in 1894. In
this competition they were the first to arrive at Mantes, doing the 36
miles in 3 hours, so that they made an average of 12 miles an hour;
they were followed very closely by the Peugeot and Panhard-Levassor
carriages. In spite of a series of difficult hills and bad roads, and
an unintentional detour, they traversed the 48 miles between Mantes
and Rouen in 4 hours 10 minutes. They recorded a speed of 15 miles an
hour on some of the level roads, and on several occasions touched a
maximum of 19 miles. The fact that they were able to ascend gradients
of 1 in 10 at a speed of from 6 to 12 miles an hour sufficiently
proved the efficiency of the machine.

The same constructors ran another vehicle in this competition of a
somewhat similar design, but not adapted for a traction engine; this
carried six passengers, and weighed about 3,000 lb. in working order.
It was mounted on a rectangular and strongly braced frame, and was
furnished with a boiler similar to that already described, but having
only some 14 square feet of heating surface, a capacity of about 6
gallons of water, and 18 rows of tubes. The ratio of gearing was 4.06;
the small cylinder was 3.54 in. in diameter and the low pressure
cylinder 5.51 in., the stroke being 3.94 in. About the same time
Messrs. De Dion and Bouton built for one of their clients a carriage
in which the driving wheels were entirely independent, each of them
being driven direct by a separate steam engine without any
intermediate gear.

[Illustration: FIG. 10.]

The Count de Dion was one of the most enthusiastic organizers of the
Paris to Bordeaux competition in 1895, and naturally his firm took
part in the trials. They entered three vehicles for competition; one
of these, called No. 1, was the traction engine which had taken part
in the 1894 trials, and which we have already described. For the
second time this machine gave very excellent results, as it made the
distance from Paris to Angoulème (280 miles) in 30 hours, but on
account of various mishaps it had to run very slowly from Angoulème to
Bordeaux (84 miles), taking, in fact, 31 hours for this part of the
journey, and not arriving until long after it had been ruled out of
the competition.

Their second vehicle, No. 2, was a four seated brake which was, in
fact, a modified traction engine. The boiler, which was of the De Dion
and Bouton type, had a heating surface of 36 square feet, and was
registered at 200 lb. per square inch; it weighed 550 lb. As to the
motor, it was a Woolfe engine, the moving parts of which were
carefully counterbalanced. The cranks were set at an angle of 180°;
the diameter of the high pressure cylinder was 2.95 in., and that of
the low pressure 5.90 in.; the low pressure cylinder was steam
jacketed. This motor, which weighed 330 lb., developed 11 horse power
at a speed of 800 revolutions. The engine was coupled direct to the
shaft of the differential motion, on which were mounted two pinions
for changing the speed, and which could be moved to and fro on the
shaft; the movement of the differential gear was transmitted to the
wheels by articulated shafts, such as those we have already referred
to in describing the traction engine; sufficient water and coke could
be carried for a run of 45 miles, and on a good road a speed of more
than 25 miles an hour was obtained.

[Illustration: FIG. 11.]

Messrs. De Dion and Bouton anticipated great things from this
carriage, and for the long run from Paris to Bordeaux they had
provided only three changes of drivers, in order that the machine
might be in as few hands as possible. Their hopes, however, were not
realized, for although it made a better start than any of the other
competitors, it only succeeded in running for 125 miles; after having
passed Blois the transmission shaft broke, and the brake was useless
for the time being, but the machine did enough to satisfy the
constructors of the soundness of their idea; it ran the 34.5 miles
between Versailles and Etampes in 2 hours and 16 minutes, making an
average speed of 15 miles an hour over difficult country; between
Versailles and Blois the speed touched nearly 18 miles.

The vehicle No. 3 was a tricycle driven by a petroleum motor; this was
not seriously entered for competition, but rather to show a first
effort of a new departure which the constructors have since followed
with some success. At the present time Messrs. De Dion and Bouton are
making preparations to take part in the competition which is to be
arranged for the autumn of the present year. They have a traction
engine with considerable modifications in its design, with which they,
expect to run from Paris and Marseilles, and they have the intention
of hauling with it one of the 40-seat omnibuses of the Paris Company,
which is usually drawn by three horses. Fig. 10 is a general view of
the engine attached to the omnibus. This type of vehicle is furnished
with a compound engine, which can be worked up to 30 horse power, and
which is to be capable of hauling a load of 5 tons at a speed of 12.5
miles; the principal points of difference between this machine and the
other, which we have already described, lie in the great care which
has been bestowed on the details, the precautions taken to secure the
moving parts from dust, and the oil bath in which the engine works.
The water supply carried is sufficient for a run of 25 miles over an
average road with a load of 3 tons; the manufacturers state that the
cost of hauling this load amounts to 1d. per kilometer.

Great care has been taken as to the quality of the steel employed in
the frame and other parts of the machine. By reference to Fig. 10 it
will be seen that the boiler (2) is surrounded by the fuel tank, while
the water reservoir forms a seat; the motor (1) is placed beneath the
platform as usual. The driver has all the controlling levers
conveniently at hand; the starting lever is shown at 9, while at 5 is
a small wheel controlling the steam admission; the reversing gear is
actuated by the lever, 7. The vehicle is steered by means of a turning
bar, similar to those of hand brakes on some wagons; the feed pump is
started and stopped by a small wheel marked 10, while 8 and 11 are the
hand and steam brakes respectively.

We referred just now to the tricycle made by Messrs. De Dion and
Bouton, and shown by them at the competition of 1895, although it was
not entered for the race. Since that time they have made two types of
this class of vehicle, of which we give engravings in Figs. 12 and 13.
In the former the motor is attached to the back of the frame by a
suspended connection. It will be seen that the frame is not a little
complex, and necessarily so, in order that it may carry the different
parts of the mechanism. The motor has a single cylinder and is quite
inclosed in a casing that is kept filled with oil; the moving parts of
the engine are within this casing; the main shaft drives, by means of
a pinion, the differential gear that is mounted on the axle. It will
be seen from the illustration that the builders do not rely wholly on
the motor, but have provided the usual cycle pitched chain so that, in
the event of a breakdown, the rider can propel his machine with the
pedals. Indeed, this is always necessary in starting, though a few
strokes with the pedals suffice, and as soon as the engine is started
the pedal clutch is thrown out of gear. In mounting a steep gradient
the pedals are also useful as an auxiliary to the motor. The
mechanical power provided is sufficient to drive the machine on a good
and level road at the rate of 20 kilometers an hour. It can also
travel up grades of 1 in 20 or 25; the weight of the machine in
working order is only 100 lb.

On referring to the engraving there will be seen attached to the frame
beneath the saddle a rectangular reservoir that contains the gasoline,
the capacity being sufficient for a six hours' run. To the reservoir
is attached the carburetor, which is connected to the motor by a pipe.
The explosive mixture in the cylinder is fired electrically, and for
this purpose a compact and reliable battery is hung to the forward
part of the frame almost beneath the steering bar. This battery will
give 100 hours of work without recharging; it supplies current to a
Ruhmkorff coil placed beneath the rear bar of the frame in a metal
case that can be seen in the engraving; the other cylinder near it is
a pressure reducer into which the gases from the cylinder are
exhausted before they pass into the air. The second type of tricycle,
illustrated by Fig. 13, is an improvement on the first. It will be
seen that the frame is much simpler; the total weight is reduced; the
gasoline reservoir is triangular, in order to economize space. The
motor employed is very ingenious, and appears to be efficient; we have
seen it in operation at the works of MM. De Dion and Bouton. It can be
run easily at a speed of 2,500 revolutions, although in practice the
rate is limited to 700 revolutions, in order to reduce the wear of the
moving parts. In this, as in the earlier type, the use of water for
cooling the cylinder is avoided, the outside of the latter being made
with a number of wings that are intended to keep the cylinder cool by
contact with the air. The method of igniting the gases has also been
changed, in so far as the arrangement of the battery is concerned. The
four cells used for this purpose are carried in a leather case hung to
one of the frames of the machine. An interesting detail is that the
exact moment for producing the spark is regulated by the motor itself,
and the Ruhmkorff coil is suppressed. The contact breaker has been
placed on the motor, and a cylindrical cam is mounted on the shaft
that controls the exhaust valve. In this cam there is formed a recess
into which the blade of the contact breaker, which is fixed on an
insulated mount, falls at the proper instant; at the same moment the
spark is produced, the blade being raised as it leaves the recess in
the cam. It is, of course, necessary to regulate exactly the relative
positions of the blade and the cam, so that the spark may take place
when the mixture has to be exploded. The frame of the motor is of
aluminum, by which considerable saving in weight is effected; as in
the earlier model, the moving parts of the motor are immersed in an
oil bath. The pedals are employed to start, or as an auxiliary, or in
the event of a breakdown. When not required for propulsion, they are
thrown out of gear, when they serve as foot rests, and also as a means
for actuating an emergency brake. The carburetor is no longer attached
to the gasoline reservoir, but is separate; the explosions in the
cylinder are regulated by a lever close to the steering bar.

The greatest credit must be accorded to MM. De Dion and Bouton for the
perseverance and ingenuity they have shown in the design and
construction of the types of power vehicle they have made their own.
As to their larger carriages, experience has proved their practical
value; they have expended even more trouble on their power cycles, but
it appears to us that ingenuity and skill are largely wasted in this
direction, since the raison d'etre of the cycle in all its forms lies
in the fact that it should give perfect freedom to the rider and leave
him dependent for his progress upon his own efforts.--Engineering.

       *       *       *       *       *




FROM NEW YORK TO HAVRE IN A ROWBOAT.


The rowboat Fox, of the port of New York, manned by George Harbo,
thirty-one years of age, captain of a merchantman, and Frank
Samuelson, twenty-six years of age, left New York for Havre on the 6th
of June. Ten days later the boat was met by the German trans-atlantic
steamer Fürst Bismarck proceeding from Cherbourg to New York. On the
8th, 9th and 10th of July, the Fox was cast by a tempest upon the
reefs of Newfoundland. The two men jumped into the sea, and thanks to
the watertight compartments provided with air chambers fore and aft,
it was possible for them to right the boat; but the unfortunates lost
their provisions and their supply of drinking water. On the 15th they
met the Norwegian three masted vessel Cito, which supplied them with
food and water. The captains of the vessels met with signed the log
book and testified that the boat had neither sail nor rudder. The Fox
reached the Scilly Islands on the 1st of August, having at this date
been on the ocean fifty-five days. It arrived at Havre on the 7th of
August.

[Illustration: THE NAVIGATORS OF THE FOX.]

Cost what it might, the men were bent upon reaching this port in order
to gain the reward promised by Mr. Fox, of the Police Gazette. Thanks
to the wind and a favorable current, they made 125 miles in 24 hours.
One slept three hours while the other rowed. Their skins and faces
were tumefied by the wind, salt water and sun; the epidermis of their
hands was renewed three times; their legs were anchylosed; and they
were worn out.

[Illustration: THE ROWBOAT FOX.]

The boat was 18 feet in length, 5 in breadth, and 23 inches in depth,
and carried a small kerosene stove for cooking.--L'Illustration.

       *       *       *       *       *




THE WASTE OF SHIPPING.


Burdensome as are the restrictions imposed upon shipowners by
legislation, considerable justification is found for them when we
compare the percentage of British vessels lost at sea with that of
foreign-owned vessels. The great shipping countries, that is, those
which have more than 1,000,000 tons afloat, are the United Kingdom,
the British colonies, the United States of America, France, Germany
and Norway. Of these six the United Kingdom suffered the least
comparative loss in its mercantile fleet in 1895. Under all the heads
of abandoned at sea, broken up or condemned, burnt, collision,
foundered, lost, missing and wrecked, the total loss was 2.99 per
cent. of the vessels owned and 2.36 per cent. of the tonnage owned. No
other of the countries named has less than 3 per cent. of loss, while
only the British colonies have less than 4, as the subjoined table
shows.

TOTAL LOSSES OF STEAM AND SAILING VESSELS IN 1895.

  ----------------------------------------------------------------+
                           |  Vessels Owned.  | Percentage Lost.  |
                           |------+-----------+-------------------+
          Flag.            |      |           | Vessels | Tonnage |
                           | No.  | Tons.[1]  |  Owned. |  Owned. |
  -------------------------+--------------------------------------+
  United Kingdom.          | 9227 |12,117,957 |   2.99  |   2.36  |
  British Colonies.        | 2307 | 1,124,682 |   3.38  |   3.70  |
  United States of America.| 3220 | 2,164,753 |   4.72  |   4.06  |
  French.                  | 1164 | 1,094,752 |   6.01  |   4.02  |
  German.                  | 1730 | 1,886,812 |   6.76  |   4.38  |
  Norwegian.               | 3041 | 1,659,012 |   7.43  |   6.46  |
  -------------------------+------+-----------+---------+---------+

    [Footnote 1: Gross tonnage for steamers; net for sailing
    vessels.]

When we turn from the contemplation of the complete fleets, and
differentiate between steam and sail, we find that the United Kingdom
no longer holds the premier position, being surpassed, as regards
steam, both by the colonies and by the United States. Steam vessels
are safer than sailing craft all over the world, partly, of course,
because their average age is less. The losses they suffered last year
are as follows:

TOTAL LOSSES OF STEAM VESSELS IN 1895.

  -------------------------+--------------------------+-------------------+
                           |      Vessels Owned.      | Percentage Lost.  |
                           +--------------------------+---------+---------+
          Flag.            |      |         |         | Vessels | Tonnage |
                           |  No. |   Net.  |  Gross. | Owned.  | Owned.  |
  -------------------------+------+---------+---------+---------+---------+
  United Kingdom.          | 6446 |5,993,666|9,695,976|   3.33  |   2.13  |
  British Colonies.        |  874 |  329,845|  542,025|   1.72  |   1.69  |
  United States of America.|  626 |  660,784|  920,672|   2.23  |   1.93  |
  French.                  |  571 |  467,553|  903,105|   4.20  |   3.42  |
  German.                  |  953 |  910,567|1,343,357|   3.04  |   2.64  |
  Norwegian.               |  586 |  285,349|  446,384|   2.56  |   2.87  |
  -------------------------+------+---------+---------+---------+---------+

The United Kingdom here stands third in the list, and curiously it
only stands second under the head of number of sailing ships lost,
while it is first as regards sailing tonnage lost. The sailing tonnage
of the United Kingdom is only about 20 per cent. of the total, while
in the colonies it is about 52 per cent. The following are the
figures:

TOTAL LOSSES OF SAILING VESSELS IN 1895.

  -------------------------+-----------------+-------------------+
                           |  Vessels Owned. |  Percentage Lost. |
                           +-----------------+---------+---------+
          Flag.            |      |          | Vessels | Tonnage |
                           | No.  |  Tons.   | Owned.  |  Owned. |
  -------------------------+------+----------+---------+---------+
  United Kingdom.          | 2781 |2,421,981 |   4.53  |   3.27  |
  Colonies.                | 1435 |  582,657 |   4.39  |   5.56  |
  United States of America.| 2594 |1,244,081 |   5.32  |   5.63  |
  French.                  |  593 |  191,647 |   7.76  |   6.83  |
  German.                  |  777 |  543,455 |  11.33  |   8.66  |
  Norwegian.               | 2455 |1,212,628 |   8.59  |   7.78  |
  -------------------------+------+----------+---------+---------+

The losses of sailing vessels are very serious among the Continental
nations, especially in Germany, where more than one in nine was lost
or condemned last year. This is greatly due to the fact that our old
ships are largely sold to the foreigner when they will no longer
comply with legislative conditions of this country. We break up a few,
but only 0.75 per cent., against 1.75 per cent. for Norway and 2.5 per
cent. for France and Germany. We are more chary of breaking up our
steamers; last year only 0.46 per cent. met this fate here, 0.34 per
cent. in the colonies, 0.32 per cent. in the United States, 0.86 per
cent. in France, 0.31 per cent. in Germany, while Norway did not lose
a single steamer in this way.

Turning now to the present year we find that in the first quarter the
vessels lost, condemned or reported missing before August 7 were,
according to returns made out by Lloyd's Register of British and
Foreign Shipping, 282 vessels, of an aggregate of 195,480 tons. These
figures are respectively 23 per cent. and 24 per cent. of the total
losses last year, thus showing a favorable beginning, for the winter
losses are naturally the heaviest. The materials of the vessels lost
were: Steel, 24 vessels of 40,474 tons; iron, 74 vessels of 78,314
tons; and wood and composite, 184 vessels of 76,692 tons. The United
Kingdom shows best under the heads of total losses and losses of
sailing vessels, but in steamers it actually comes last among the six
nationalities we have selected for comparison. It must be remembered,
however, that the British fleet is large enough for a very fair
average to be attained in three months, while in all other fleets a
single loss, more or less, makes a great difference to the figures of
merit. The steam tonnage of the United Kingdom is more than seven
times greater than that of Germany, which is our chief competitor. In
sailing tonnage we do not hold this immense superiority, our amount
being only about double that of the United States and of Norway
respectively.

When we examine the various causes of loss of vessels at sea, we find
nearly 43 per cent. of the tonnage under the head of "wrecked," which
includes vessels lost through stranding, or through striking rocks,
sunken wrecks, etc. Next come 22 per cent. broken up or condemned; 14
per cent. lost, missing; 8 per cent. lost by collision; 4.3 per cent.
burnt; 5 per cent. abandoned at sea; and 3.6 per cent. foundered. The
following table shows the mercantile marine of the world, according to
Lloyd's Register, at the end of March, 1896:

      Flag.                       Steam and Sailing
                                   Vessels Owned.

                                   No.      Tons.
British. /United Kingdom.         9227    12,117,957
         \Colonies.               2309     1,124,682
America, United States of.        3220     2,164,753
Austro-Hungarian.                  309       304,970
Danish.                            812       356,714
Dutch.                             458       446,861
French.                           1164     1,094,752
German.                           1730     1,886,812
Italian.                          1239       778,941
Norwegian.                        3041     1,659,012
Russian.                          1086       487,681
Spanish.                           748       554,238
Swedish.                          1432       497,877
Other European countries.         ....     .........
Central and South America.        ....     .........
Asia.                             ....     .........
Other countries.                  ....     .........

--Engineering.

       *       *       *       *       *




NEW METHODS OF BUILDING CONSTRUCTION AT PARIS.


During recent years an interesting change has been gradually brought
about in the various methods of building construction employed in
France, and more especially at Paris, where the size and importance of
public buildings and the many-storied houses divided up into flats
necessitate special systems of construction, which possess the
advantages of combining economy in cost with strength and durability.
Parisian architects and builders, although far from approving the
extremes to which their American confrères go in the employment of
iron for the construction of their somewhat exaggerated sky-scraping
buildings, in which the style of architecture employed is often
scarcely logical or consistent with the modern methods of
construction, are nevertheless obliged to own to the necessity and the
utility of employing iron in moderation for the framework of their
buildings. Up to the present the use of iron in its ordinary form has
chiefly been confined to floors, partitions, and roofs, where, as a
rule, its presence is masked by coverings of cement, wood, or stone,
except in recent examples of the new style of buildings destined for
brasseries or drinking halls, where the iron construction is left
visible, and emphasized by means of bronze or color painting and
mosaic work, or, again, in the few examples of well known work where
the architect has endeavored to obtain a decorative effect by means of
iron lintels and columns. But where the use of iron is fast finding
favor at Paris is in its employment in combination with other
materials such as cement or concrete, and in a special form known as
the cement armé systems, in which iron or steel is employed in the
form of thick wire, trellis, or light bars embedded in cement or
concrete. This method of construction, of which there are three
different systems, has for some time been employed in the construction
of various buildings of more or less importance, and has given proof
of its strength and practical use as well as its advantages when
employed for floors, partitions, walls and roof, both as regards its
conveniences for internal arrangements, its economy, and as regards
the manner in which it lends itself to modern schemes of polychrome
decoration.

Two of these systems have been employed by the architect of the new
building now being constructed in the Rue Blanche for the Society of
Civil Engineers of France. The third system is much employed by M. De
Baudot in various buildings designed by this architect, an advocate of
rational construction and design and the logical employment of modern
building materials. It will be interesting to examine the merits of
each system as employed in these buildings, together with any other
points of construction worthy of remark.

The building for the Society of Civil Engineers is remarkable from
several points of view as regards construction and the arrangement of
plan. The façade and plans will appear in the Building News as soon as
the work is completed, and will form an interesting subject for
comparison with the building recently completed for the English
Society of Engineers, and with that about to be commenced at New York
for the American Society.

Before entering into a detailed description of the system employed, a
summary idea of the plan and general scheme of construction will not
be uninteresting. The architect, M. Fernand Delmas, has endeavored to
construct the building on economical lines, employing to a large
extent iron and those modern materials which have been tried and found
fitting as regards suitability and economy; the building will cost
£22,000, and it has been made a sine qua non that all the contractors
shall be members of the Society of Engineers.

The length of the façade is 100 ft.; the total depth of the building
is nearly equal to the frontage; the height from pavement to cornice
is 60 ft. The façade is built of solid stonework throughout its length
and height. The thickness of the masonry is 24 in. at the lower
stories and 18 in. at the upper portion. The façade wall is really the
only portion of solid masonry work in the whole building, and forms a
decorative mask to the body of the building, which is constructed of a
framework of iron. The chief supports of the building proper consist
of four framed iron uprights, 16 in. by 16 in. rising from the
basement to the roof. These uprights are solidly trussed and held
together at the floor levels by strong iron girders supporting the
iron joists of the upper floors and the light partitions which divide
up each story. This system is at once economical and practical. The
whole building is thus self-supporting, and the thick walls which
would otherwise be necessary for carrying the upper floors are thus
avoided.

[Illustration: CEMENT ARMÉ CONSTRUCTION OF FLOORS, PILLARS AND
ARCHES.]

The façade wall is built according to the system always employed at
Paris, and is formed of blocks of stone roughly cut at the quarries to
the outside dimensions of the proposed moulding and decorative work.
As soon as the whole front is erected the work of cutting it into
shape will commence, the mouldings, pilasters, and all carving work
being done while the interior is being prepared. The buildings at
Paris are by this means erected much more rapidly than when the stone
is dressed or moulded before being put into place. Greater facilities
are thus given for studying the general ensemble of the façade and the
proper scale to be given to the mouldings and decoration. The stone is
as a rule soft when first from the quarries, but becomes hard and
durable after dressing and exposure to the air. The courtyard wall of
the building is formed of light brick or metallic fillings between the
iron uprights and the party walls.

The ground floor comprises a large entrance hall or vestibule, 40 ft.
by 44 ft., forming, with the cloakroom, the principal staircase, the
rooms for the concierge, and the area, the whole front of the
building. This large vestibule is vaulted over by means of one of the
systems of cement armé to be described. The floor is constructed on
another similar system, and will be paved with mosaic work. The ground
floor of the courtyard will be occupied by the conference hall, 50 ft.
by 50 ft., to hold 300 seats. An annex, 50 ft. by 20 ft., adjoining
this hall, will open on the same by a large arched bay, and may be
separated from the larger hall by means of a special system of wooden
soundproof roller shutters. The floor of the large hall will be a
movable one, to be raised or lowered by an ingenious system of
hydraulics, and capable of being placed in an inclined position for
conference meetings, or raised to a horizontal position for ball room
purposes.

The entresol floor will comprise a large room for meeting, smoking and
conversation rooms, and a reading room, to be used as a club for the
members of the society. The first floor will contain the offices of
the society, a large committee room, and all conveniences. The second
floor will be devoted entirely to the purposes of the important
library, comprising the library proper, a room 45 ft. by 25 ft. by 17
ft. high, rising to the ceiling of the low story above, and lighted by
a large semicircular bay at either end: the surrounding rooms of the
height of the second floor will be destined for the librarian,
catalogues, drawing office, and library offices. The third floor will
be devoted entirely to the purpose of storing the books of the
library, in low rooms communicating by means of the gallery
overlooking the library below, which will be crossed by means of a
light, iron bridge. The bookcases will be suspended from the upper
floor, and will be arranged in vertical tiers hung on rollers, after
the system employed at the British Museum. The roof story will be
divided up into an apartment for the chief secretary, and reached by a
private staircase from the ground floor. The large basement, occupying
the whole of the ground surface of the building, will be used for
storing the records of the society, and will contain the heating
apparatus, stores, etc. A hydraulic lift will afford access to the
landings of each floor. The chief feature of the façade, which is
simple in style, is the wide arched bay, 24 ft. across, rising from
the pavement to above the cornice; this bay will be filled in with an
open decorative framework of wrought and cast iron.

Some of the most interesting points of the construction, besides the
large use of iron, are the systems employed in the construction of the
floor. The ground floor is built after the Coignet system, composed of
light iron bars and cement; the first floor and its supporting pillars
and arches is constructed after the Hennebique system of cement armé;
the upper floors are formed of iron joists, filled in either with the
system of light supports and plaster, much employed at Paris, or with
terracotta fillings between joints. The roof is lined internally with
agglomerated cork bricks, affording protection from excessive heat or
cold, and the walls of the area will be lined with opaline, a vitreous
material of a bluish white color, which in this case will insure
cleanliness, and afford additional light; the lavatories and water
closets will also be lined with the same material.

Speaking of the Hennebique system of cement armé, employed for the
arches and floor of the first story, it will be interesting to
illustrate the method by a few sketches, explaining the theory of this
system, which has been put to practical proofs in a large number of
buildings, chiefly for industrial purposes, in the north of France.
The perspective section will give an idea of the construction as
employed in the building for the civil engineers, a system which holds
its ground well against its rivals of other methods of cement
armé.--The Building News.

       *       *       *       *       *




BELLEEK CHINA.


Belleek porcelain (frequently pronounced "Bleak" by those who do not
know the derivation of the name) is a thin eggshell ware of great
lightness and translucency, characterized by a creamy, or sometimes
grayish, tint, and usually covered with a delicate pearly or lustrous
glaze. It is in reality a variety of Parian ware, being formed in the
same manner by the process called casting, or pouring diluted clay or
slip of the consistency of cream into plaster moulds, which, by
absorbing a part of the moisture from the portion of the liquid
preparation in direct contact, retain a thin shell of partially dried
clay after the superfluous contents are taken out. After standing a
few minutes the thin cast can be liberated from the mould. The
thickness of the walls, of course, depends upon the length of time the
slip is allowed to remain in the mould before the surplus is removed.
By this ingenious method cups, saucers and other forms of ware can be
made almost as thin as an egg shell or a piece of heavy paper, and
after being allowed to become thoroughly dry can be safely burned in
the kiln. It can readily be understood that it would not be possible
to make such fragile pieces by the usual processes with plastic clay,
which must be of the consistency of putty or dough, on the potter's
wheel or by pressing in moulds.

Belleek ware was first made at Stoke upon Trent by the eminent potter
William Henry Goss, who invented the body or composition some
thirty-five years ago; but it was not then known by this name. Soon
after its introduction Messrs. McBirney & Armstrong induced some of
Mr. Goss' workmen, including his manager, William Bromley, to join
them at their porcelain works, then recently started (in 1863) in the
town of Belleek, County Fermanagh, Ireland, and the art was
established so successfully there that the name of the village was
given to the ware which has since become so noted. The distinguishing
characteristic of this beautiful product is its lustrous glazing,
which varies in form from white to yellow and through graded tints to
a dark leaden hue.

Mr. Goss has continued to manufacture this dainty variety of porcelain
until the present time, and his factory has become one of the most
noted in the British empire. Among the most popular of his productions
in this body are loving cups and little cream jugs, cups and saucers,
and fairy tea sets embellished with beautifully colored crests and
coats of arms of the different English cities and of prominent
personages, such as Queen Elizabeth, Sir Walter Raleigh, King Henry of
Navarre, Queen Victoria, the Prince of Wales, Shakespeare, Sir Walter
Scott, and Robert Burns.

Of more interest, perhaps, to Americans are the porcelain tumblers
which have just been produced at the same factory, bearing on the
front a faithful duplication in blue and yellow enamels of the
insignia of the society of Sons of the Revolution, which were made at
the suggestion of a member of the society in Pennsylvania. The soft,
satiny Belleek body seems to be particularly well adapted to show off
to advantage the rich designs of these badges, and this suggestion
will doubtless be followed by other patriotic hereditary societies in
the United States.

John Hart Brewer, of Trenton, first attempted the manufacture of
Belleek ware in this country. He commenced his experiments in this
line in 1882, and in the following year brought over from England
William Bromley and his son from the Belleek works in Ireland.
Subsequently the elder Bromley joined the Willets Manufacturing
Company, of the same place, and introduced the manufacture of eggshell
porcelain there, and at the present time there are no less than five
or six establishments in Trenton where the same class of ware is made.

Among many specialties recently introduced is a new style of
decoration which has been worked out by Miss Kate Sears, a Kansas girl
who studied modeling in Boston. Going to Trenton for the purpose of
pursuing her studies in this direction, one day in 1891, while engaged
in working over the wet Belleek, the idea of carving delicate designs
in the dry clay occurred to her, and after conducting a series of
experiments her efforts were crowned with success. The process of
modeling which Miss Sears has originated is as follows: A vase or
other piece which has been formed in the wet clay and dried is taken
before it has been in the kiln, and with knives or other tools the
design is cut or chiseled so as to leave the background as thin and
transparent as possible when finished. As the dry Belleek, besides
being thin, is extremely brittle, and crumbles easily, the carving is
an exceedingly difficult operation. It is necessarily a very slow
process, since at any moment the knife is liable to cut through the
wall and ruin the piece.

The result of this process is a clear cut, chiseled effect, which
cannot be obtained by moulding or casting, a moonlight effect of fairy
like character, most beautiful in conception, and possessing marked
originality. While sometimes several weeks are consumed in executing a
single piece of the carved ware, Miss Sears has produced a large
number of such designs, each one of which is a perfect work of art,
reflecting credit upon the artist and the manufacturers.

The marks which appear on the various productions of Belleek porcelain
are of considerable interest to collectors and admirers of this
beautiful ware. Mr. Gross has adopted as a factory mark his family
crest, a falcon rising ducally gorged, which is printed on each piece
in black. The mark of the Belleek factory in Ireland, consists of the
four Irish emblems, the watch tower, the hound, the harp of Erin, and
the shamrock, and is printed on the ware in green or black. At the
Etruria Pottery, formerly operated by Messrs. Ott & Brewer, now known
as the Cook Pottery Company, the mark used on Belleek ware was a
crescent bearing the name with the initials of the proprietors, "O. & B."
The Willets Manufacturing Company uses for a factory mark on its
decorated Belleek pieces the figure of a serpent looped in the form of
a W, which is printed in red. On similar ware produced by the Ceramic
Art Company is printed in red a design composed of a painter's palette
and a circle inclosing the monogram C. A. C., while Messrs. Morris and
Willmore, of the Columbian Art Pottery, employ a shield with the
initials of the firm name, M. W.

The manufacture of Belleek ware was introduced into this country by
English potters who had learned the processes at the potteries in
England and Ireland, and we cannot, therefore, lay claim to
originality so far as the product itself is concerned; yet, in a
measure, the ware as made in America differs materially from the
foreign in many respects, and has been developed in new directions, so
that it has come to have distinctive characteristics of its own which
entitle it to be ranked with original American productions. While our
potters, perhaps, have not yet reached the high degree of elaborate
modeling which characterizes some of the imported Belleek, they have
already surpassed the foreign manufacturers in the simplicity and
elegance of their forms and the artistic quality of their decorations,
while in delicacy of coloring, in the excellence and lightness of
body, the American products are not surpassed. A visit to the
showrooms of the Trenton potteries will prove a revelation to those
who still believe that no artistic china is made in this
country.--Edwin Atlee Barber, in China, Glass and Lamps.

       *       *       *       *       *




GOODMAN'S HATCHET PLANIMETERS.


The instrument we are about to describe is an improvement on the
hatchet planimeter and is due to Prof. Goodman, of Leeds. One form of
the instrument is intended for the measurement of areas of surfaces,
and the other form for the measurement of the mean height of a figure
such as an indicator diagram.

London Engineering, to which we are indebted for the cuts and copy,
describes the instruments as follows: The method of using the two
instruments is practically the same, but for the present we shall
confine our remarks to the instrument for measuring areas. In order to
familiarize oneself with the peculiar action of the instrument, it
will be well to get a large sheet of paper on a drawing board or a
large blotting pad, and holding the instrument vertical to the paper,
grasp the tracing leg very lightly indeed between the forefinger and
thumb of the right hand, with the hatchet toward the left hand, as
shown in Fig. 1. Then by moving the tracing point round and round an
imaginary figure and allowing the hatchet to go where it pleases, it
will be seen that the hatchet moves to and fro along zigzag lines, and
travels sideways--the side travel being nearly proportional to the
area of the figure described by the tracing point. If the tracing
point be too tightly grasped, the hatchet will not move freely, and,
will have a side slip. When this occurs the side travel of the hatchet
ceases to be proportional to the area traced out. A loose weight is
hung on the hatchet to prevent this side slip, but as soon as a little
skill is attained in the use of the instrument, this weight may be
dispensed with.

[Illustration: GOODMAN'S HATCHET PLANIMETER.]

When measuring the area of such a surface as that inclosed by the
boundary line shown in Fig. 3, a point, A, is chosen somewhat near the
center of the figure; the exact position is, however, immaterial. From
the point, A, a line, AB, is drawn in any direction to the boundary;
the tracing point of the planimeter is now placed at A, with the
hatchet at X, Fig. 3, that is, with the instrument roughly square with
AB. The hatchet is now lightly pressed in order to mark its position
on the paper by making a slight dent, then leaving the hatchet free to
move as shown in Fig. 1, the tracing point is caused to traverse the
line, AB, and the boundary line in a clockwise direction, as shown by
the arrows, returning to A via AB. The hatchet will now be found to
have taken up a new position, Y, which must be marked by again
pressing the hatchet to make a slight dent in the paper. If the figure
under measurement be on a separate sheet of paper, the paper must now
be revolved about the point, A, through about 180 deg. (by eye), using
the tracing point of the instrument as a center, care being taken that
neither the point nor the hatchet be shifted while the paper is being
turned. The line, AB, will again be roughly at right angles to the
instrument, but in the reverse direction (see dotted lines in Fig. 3).
Again cause the tracing point to traverse the line, AB, and the
boundary line as before, but this time in a contra-clockwise
direction. The hatchet after this backward motion will take up the new
position, X1, which may or may not coincide with X; if not, prick a
central point between X and X1, as shown, then, of course, the
distance of this point from Y is the mean side shift of the hatchet;
this distance measured from the zero of the scale on the back of the
instrument is the area of the figure in square inches. The scale is
read in exactly the same manner as a geometrical scale on a drawing,
the whole numbers being read to the right of the zero and the decimals
to the left. The instrument does not profess to give results nearer
than one-tenth of a square inch.

In some cases on large maps, for example, the figure cannot be turned
round as indicated above; in that case the instrument itself must be
turned round through 180° and two fresh dents, X¹Y¹, obtained; the
area of the figure is then the mean of the two readings, XY and X¹Y¹.

When the area is large the instrument will move through a large angle,
and consequently, if square with AB to start with, it will be
considerably out of square at the finish. In such a case it is only
necessary to see that the mean position of the instrument is square
with AB.

By carefully examining the scale it will be observed (see Fig. 1) that
the divisions are not equal, but that they gradually increase from
zero upward; herein consists the improvement of this instrument over
the ordinary hatchet planimeter invented by Knudsen, of Copenhagen,
who shows in a pamphlet published by him that

         c1 + c2
  I = -------------  p  [1 - (R / 2p)²]
            2

  Where I = the area traced out by the pointer in square inches.

  c1 = the distance between the dents, X and Y, in inches.

  c2 = the distance between the dents, X1 and Y, in inches.

  p = the length of the instrument from center of hatchet to point
  in inches.

  R² = the mean square of the radii of the figure.

The making of such a calculation for every area measured is, of
course, quite out of the question. The labor involved would be as
great as calculating the area by the ordinate or by Simpson's method;
hence it is usual to neglect that part of the formula inclosed within
the square brackets, which amounts to assuming the area to be equal to
the product of the mean side shift of the hatchet by the length of the
instrument; this, however, involves an error too big to be neglected,
and, moreover, one that is not a constant fraction of the area
measured, thus:

  Area of circle, square inches.       10   20   30   40
  Error per cent.                      0.8  1.6  2.4  3.2

These errors are, however, compensated for in Goodman's improved
instrument by making the scale with constantly and regularly
increasing divisions. If, however, the area dealt with be not a
circle, the error involved in assuming that its R² is equal to the R²
of a circle of equal area is so small that it is quite inappreciable
on a scale which only reads to one-tenth of a square inch. If the R²
for any given area were say 5 per cent. greater than that of the
equivalent circle, the error involved would be 0.0016 of the whole
quantity when measuring an area of 40 square niches, or 0.064 square
inch, a quantity which cannot be measured on the scale. It has been
proposed to use a roller and vernier to enable the readings between
the dents to be measured with a greater degree of accuracy, but it
will be readily seen that the instrument is not reliable to the second
place of decimals, hence such refinements are only imaginary. Even
with this special scale that we have described above, the inventor
does not profess to get as good results as with an Amsler planimeter;
he regards his instrument as equivalent to a foot rule in comparison
with a micrometric gage as representing Amsler's instrument; but for a
great number of purposes the foot rule is sufficiently accurate, and
only when great accuracy is required will a micrometer be used, so
with the two forms of planimeter. The rougher instrument has some
advantages, however; there are no delicate moving parts to get out of
order, and the cost is but one-fourth.

In order to ascertain the relative accuracy of various methods of
measuring areas, Prof. Goodman has had a large number of irregular
areas measured by his first year students within a week or so of their
entering the department, before they have attained to any degree of
skill in using instruments. The results were as follows. Amsler's
planimeter was taken as the standard, the area measured by it being
independently checked by an assistant.

                                         Measurement of Areas
  Method.                                  Reduced to 100.
  Amsler planimeter                        100
  Goodman  "                               100 + or - 0.6
  Simpson's rule                           100 + or - 1.0
  Mean ordinates                           100 + or - 2.4
  Cutting out in cardboard and weighing
    against piece of known area            100 + or - 4.4
  Equalizing curved edges by drawing
    straight lines along boundary
    and calculating by triangles           100 + or - 7.0

In the averaging instrument for getting mean heights of figures, the
length of the instrument between the hatchet and the pointer is
variable. The length is set to the length of the diagram (see Fig. 2);
it is then used in precisely the same manner as the planimeter
described above. From what we have already said, our diagram in Fig. 5
will be perfectly clear. The mean distance between the dents is in
this case the mean height of the diagram, measured on an ordinary
scale, or the mean pressure in the case of an indicator diagram
measured on a scale to suit the indicator spring.

Knudsen's formula given above applies equally well to this averaging
instrument. Neglecting for the moment the quantity in the square
brackets, we have I = c p where c = (c1 + c2)/2 but we also have
I = h l where h is the mean height and l the length of the figure,
therefore h l = c p; but in this instrument we make p = l. Hence h =
c, or the mean height of the figure is equal to the mean distance
between the dents. The quantity in the brackets is too great to be
neglected, however. If we were always dealing with circles, the
ratio (R/2p)² would be a constant, and numerically equal to 1/16 or
6.25 per cent. Then all we should have to do would be to use a scale
6.25 per cent. longer than the true scale. But with a long narrow
figure such as an indicator diagram, this ratio is much smaller. The
measurement of a large number of diagrams gave a mean value of 1/60
for diagrams 4 in. long. It is obvious that, if a diagram be
shortened, this ratio will increase, for the value of R does not
decrease as rapidly as p, and vice versa; hence this ratio varies
approximately inversely as the length of the diagram. Taking the value
of 1/60 for the 4 in. diagram, this is equivalent to saying that there
is an error of 1 in 60, or 1.67 per cent., in the result, and from the
formula it will be seen that the result is too great by this amount;
hence, if we make the length, l, between the legs of the instrument
1.67 per cent. of 4 in., or 0.067 in. less than the length from the
tracing point to the center of the hatchet, p, we shall compensate for
the error on a diagram 4 in. long. But the ratio of this constant
quantity 0.067 in. to the length of the diagram also varies inversely
as the length in just the same manner as the ratio R/2p, hence this
method of correcting the instrument is approximately right for all
lengths of diagrams. It must be remembered that if this correction
were entirely neglected, it would not exceed two per cent.; hence any
inaccuracy in this correction is an exceedingly small quantity, well
under 1 per cent.

Whenever errors have been attributed to the instrument, on examination
it has always been found that they were due to carelessness in setting
the length to the diagram, or to the tracing leg having been grasped
so tightly as to cause side slip.

The accuracy of the instrument may be easily demonstrated by drawing a
rectangle, say about 4 in. long and 2 in. high, and finding the mean
height by the averager, then by doubling the paper over and comparing
its height with the mean distance between the dents, it will be found
that they agree if the instrument has been carefully used.

In many quarters we know that there is a great deal of prejudice
against instruments of this kind. We are quite sure, however, that if
only draughtsmen and others would spend half an hour in trying them
over, they would save themselves many hours of tedious labor in
calculating areas by methods which are seldom as accurate as the
results obtained by a planimeter in the same number of minutes.

       *       *       *       *       *




APPARATUS FOR THE MANUFACTURE OF ACETYLENE GAS.


We give herewith, from Le Genie Civil, illustrations and brief
descriptions of some of the more prominent apparatus used for the
manufacture of acetylene gas.

Trouvé Apparatus (Fig. 1).--The principle of the gas generator is that
of the hydrogen briquet already applied by Mr. Trouvé in his portable
lamp. It consists of two vessels, one entering the other. The internal
vessel is provided at the bottom with a discharge pipe communicating,
through a cock, with the gasometer. It carries a suspended open work
basket containing the carbide of calcium. The bottom of this vessel is
provided with an aperture through which it communicates with the
external vessel containing the water. The latter is brought to a level
in the two vessels and attacks the carbide. The acetylene formed is
disengaged and enters the gasometer. At the same time, the excess of
pressure forces back the water into the external vessel in suppressing
its contact with the carbide. The latter, nevertheless, continues to
be attacked slowly through the action of the aqueous vapor. If the
cock of the apparatus now be closed, the gas will accumulate in the
interior vessel and will soon escape through the aperture in the
bottom in raising the column of water. Mr. Trouvé has endeavored to
remedy this inconvenience by arranging the pieces of carbide in the
basket in distinct layers separated by disks of glass. He has,
besides, provided his apparatus with an electric alarm, designed to
give warning when the holder is too full or when it is on the point of
being empty.

[Illustration: FIG. 1.--TROUVE'S ACETYLENE APPARATUS.]

Clauzolles Apparatus (Fig. 2).--This apparatus consists of a gas
generator, A, hermetically closed and containing the carbide, of a
water reservoir, B, communicating with A through a cock, H, and of a
gasometer, D, connected with A by the tube and cock, A. The cock, H,
is provided with a lever fixed by its extremity to a chain that
follows the motions of the holder. When the latter rises or descends,
it causes the cock, H, to close or open.

[Illustration: FIG. 2.--CLAUZOLLES' ACETYLENE APPARATUS.]

The receptacle, A, is held by a cover fixed by means of four nuts
which are removed when it becomes necessary to renew the carbide. The
receptacle is removed and replaced by a duplicate one, after the cock,
K, has been closed so as to keep the gas in the gasometer.

Bon Apparatus (Figs. 3 and 4).--The acetylene is produced by the
reaction of the water falling in small quantity upon the carbide
contained in the gas generator, A. The latter is divided into
compartments, F, which, filled with carbide, are reached by the water
only successively and progressively. When the carbide of the first
compartment is exhausted, the water enters the second, and so on. The
dimensions and numbers of these departments vary with the size of the
apparatus. Each of them contains from ½ lb. to 4.5 lb. of carbide. The
box with compartments, F, is covered by a rectangular holder, H, which
enters a flat-bottomed receptacle, E, opened above and filled about
two-thirds full of water. The latter serves as a hydraulic joint, and,
at the same time, as a refrigerator. The holder, H, carries a lead
pipe, G', terminating in a funnel into which falls the water from the
reservoir, C, led by the pipe, G. This water flows through the
extremity, i, of the pipe, G', into the first compartment. Each of the
compartments carries, upon the top of the partition that separates it
from the following, an aperture through which the water enters the
adjoining compartment as soon as the gas in the preceding compartment
has made its exit from the gasometer, and so on until the last in the
order of the numbers of the compartments.

[Illustration: FIGS. 3 AND 4.--BON ACETYLENE APPARATUS]

The flow of the water through the pipe, G, is regulated automatically
by a cock, r', with counterpoise. The holder, in rising, closes this
cock and gradually cuts off the entrance of the water. The gas
produced, once consumed, the holder descends in opening the cock, and
the water begins to flow again.

The disengaged acetylene enters the gasometer, B, through the pipe, D.
The extremity of the latter is bent into the form of a swan's neck.
The gas is thus forced to bubble up through about 2 in. of water, in
which it is cooled and freed from all traces of the ammonia that it
may contain. The cock, R, in the pipe, D, is a three-way one. The
first opens and the second intercepts communication between the gas
generator and the gasometer, while the third puts these two parts of
the apparatus in communication with the atmosphere.

The total capacity of the gasometer is so calculated that the
acetylene produced by a single one of the compartments, F, may be
stored up therein upon its exit from the gasometer through the pipe,
K. The acetylene traverses a purifying column, I, filled with pumice
stone saturated with a solution of sulphate of copper and surmounted
by a thin layer of carbide of calcium. The object of the sulphate of
copper is to free the gas from phosphorus and arseniuret of hydrogen.
The layer of carbide serves to dry it.

It is well to use salt water for the gasometer, as acetylene is but
slightly soluble therein.

Lequeux-Wiesnegg Apparatus (Figs. 5, 6, and 7).--The apparatus
represented in Fig. 5 is capable of being used in lecture courses. It
consists of a tank, B, and a holder, A, which is provided at the top
with a wide aperture closed by a hydraulic plug, F. When the apparatus
is at the bottom of its travel and ready to be filled with acetylene,
the plug, F, as well as the basket, D, and the bucket, E, are removed.
The quantity of carbide necessary to fill the gasometer is introduced
into the basket. After care has been taken to put a certain quantity
of water into the gutter forming the hydraulic joint of the plug, F,
the parts, E, D, F, are introduced into the tube, C, in operating
rapidly enough to prevent the loss of gas. The holder immediately
rises as a consequence of the production of acetylene. The gas
redescends through a tube to the bottom of the tank and rises
laterally in a column by serving as a guide to the holder and as a
support to the cocks designed to send the gas to the points of
utilization. A cock, H, placed at the lower part of the apparatus,
permits of clearing the piping in case a condensation of water occurs.

[Illustration: FIGS. 5, 6, AND 7.--LEQUEUX-WIESNEGG ACETYLENE
APPARATUS.]

The apparatus represented in Figs. 6 and 7 is continuous. It consists
of an apparatus with two holders, that is to say, so arranged as to
put the least liquid possible in contact with the gas produced, and to
thus prevent absorptions and losses. This gasometer consists of a
tank, A, of a movable holder, C, and of a stationary holder, B. The
generator, E, is formed of a cylinder, at the bottom of which there is
a bucket, F, designed for the reception of the greater part of the
lime resulting from the reaction. It is closed by a cover, G, arranged
with a simple or multiple joint, according to the precision that it is
desired to obtain and that may reach 30 centimeters of water. The
figure represents the holder at the bottom of its travel.

Mr. Edward N. Dickerson's Apparatus (Figs. 8 to 13).--Mr. Dickerson,
of New York in June, 1895, patented several arrangements permitting of
automatically regulating the production of acetylene in measure as it
is consumed. In the apparatus represented in Fig. 8 the water is led
from a sufficiently high reservoir, A, through the pipe, B, into the
gas generator, D, and over the carbide, C, placed upon a grate, O. The
acetylene forms when the water reaches the carbide, and its
disengagement ceases when the pressure forces the water back. The gas
passes through the intermedium of a cock, e, into the pipe, W,
provided with a cock, Z, into the automatic regulator, G, and then
into the gasometer, P R. Between the regulator, G, and the gasometer,
Mr. Dickerson interposes an arrangement consisting of an engine, H,
actuating an air pump, K, through the pressure of the gas when it is
desired to introduce a mixture of acetylene and air into the
gasometer. This arrangement is evidently useless when it is desired to
collect the acetylene alone. The gas upon making its exit from the
gasometer flows through the pipe, T, to the burners, V.

[Illustration: FIG. 8.--DICKERSON ACETYLENE APPARATUS, WITH AUTOMATIC
REGULATION]

When the holder, R, is filled, the cord or chain, a, passing over the
pulley, b, revolves the sector, c, until the pin, g, meets the
counterpoised lever, d, of the stopcock, e. In the return of the
chain, the other pin, o, carries the lever back to the position shown
in the figure.

The gas generator, D, is provided with a discharge cock, E, and a
charging aperture, m.

Figs. 9 to 13 show another of Mr. Dickerson's apparatus that permits
of an intermittent automatic distribution either of the water upon the
carbide or of the carbide in the water in regulating such distribution
through the displacement of the holder of a gasometer that collects
the excess of gas necessary for the consumption.

[Illustration: FIG. 9.--DICKERSON ACETYLENE APPARATUS, PERMITTING OF
THE AUTOMATIC INTERMITTENT DISTRIBUTION OF WATER UPON CARBIDE OF
CALCIUM.]

Mr. Dickerson rightly remarks that it is disadvantageous to directly
control the distribution of the water upon the carbide by means of the
holder of the gasometer. In fact, the water cock may remain open
before the holder has moved, and there may thus fall upon the carbide
an excess of water, giving rise to a production of acetylene greater
than the capacity of the holder warrants.

The object of the Dickerson apparatus is to prevent such
overproduction and to furnish water or carbide to the gas generator
only as long as the gasometer will have been emptied of the desired
quantity of gas.

Fig. 10 shows a modification of the gas generator relative to the
introduction of the carbide into the water; but the same letters
designate the same parts. We shall describe the operations
corresponding to the figures.

[Illustration: FIG. 10.--MODIFICATION OF THE GAS GENERATOR OF THE
DICKERSON APPARATUS.]

1 represents the gasometer; 4, the gas generator; 11, the funnel
through which the water is introduced into the generator through the
pipe, 13; 12, the pipe that connects the generator with the gasometer;
5, a stopcock with counterpoise that alternately opens and closes the
communication between the funnel and the generator; 10, a lever
connected with the cock, 5; 2, a chain that moves with the holder and
maneuvers the lever, 10.

The plug, 6, of the cock, 5, is provided with two conduits, 7 and 8,
at right angles. This plug turns 90 degrees, when it is maneuvered by
the chain of the gasometer. In the position shown in Fig. 13 the
holder is at the top of its travel, and the counterpoise, 9, of the
cock is in the position marked by dotted lines in Fig. 9.

[Illustration: FIGS. 11, 12, AND 13.--DETAILS OF THE DICKERSON
ACETYLENE APPARATUS]

In this case, a charge of water fills the chamber 7 and 8 of the cock.
This chamber may be oblong, as shown in Fig. 12, in order to increase
its capacity. On the contrary, in the position of the counterpoise, 9,
marked in continuous lines in Figs. 9 and 11, the channel, 8,
communicates with the pipe, 13; the charge of water of chamber, 7 and
8, has fallen upon the carbides, but another quantity of water has not
been able to enter, because the revolution of the cock has cut off all
communication between the funnel, 11, and the generator, 4.

The acetylene produced by the reaction of the water upon the carbide
raises the gasometer holder, which then actuates the plug, 6, of the
cock, 5, and allows a new charge of water to enter the chambers, 7, 8.
It is only when the holder descends anew to the position, 1, that the
water in the chamber, 7, 8, can fall upon the carbide. The quantity of
water that the cock is capable of containing is not sufficient to
produce a quantity of gas exceeding the capacity of the gasometer,
and, as it is impossible to introduce another quantity of water as
long as the gasometer has not been emptied anew, any overproduction of
gas is thus rendered impossible.

Fig. 10 applies to the introduction of the carbide into the water. It
is necessary in this case that the carbide shall have been previously
reduced to powder. The funnel, 11, is then closed by a cover, 21, in
order to prevent any accidental escape of the gas. The carbide falls
into the generator, the bottom of which is open. The latter enters a
tank into which flows a current of water, escaping through the waste
pipe, 19, in carrying along the lime formed. The height of the water
in the tank is sufficient to furnish the pressure necessary to allow
the gas to enter the gasometer through the pipe, 12.

       *       *       *       *       *




DEVICE FOR THE DISPLAY OF LANTERN SLIDES.


Those who would wish to have a little extra shop window attraction by
way of displaying slides for the season now at hand might do worse
than resort to something of the following style. The appliance can
hold any number of slides, according to the diameter of the wheel
portion, but in the diagram herewith it is for holding a dozen. The
slides can be changed readily, hence a little time would be expended
in making a complete change at least once a day.

[Illustration: FRONT ELEVATION.]

The relative portions of the sketch being to scale, particulars as to
the making of the revolving wheel need not be entered into, as any
mechanic could grasp the whole idea at a glance. The edge of the wheel
should, of course, be placed facing the window, and a band on the
pulley wheel, A, attached to a clockwork or electric motor would
supply all the driving power necessary.

In order to get good illumination on the slides, it will be necessary
to have a piece of white cardboard or opal glass, B, hung on the axle,
the lower side being the heavier, so that although the wheel revolves,
it will remain stationary.

Various devices may be resorted to for hanging the slides on the cross
rods, but perhaps the method shown at C will prove as simple as any,
and consists of small springs which grip the slide at both sides.

[Illustration: SIDE ELEVATION.]

By the judicious arrangement of shielded lights placed at side of
reflector, a pretty effect is produced as each slide is gradually
brought to view.--The Optical Magic Lantern Journal and Photographic
Enlarger.

       *       *       *       *       *




THE FECULOMETER.


The selling price of beets naturally depends upon their yield in
sugar, and what gives potatoes their value is their yield in fecula or
starch, a product that serves to nourish man and animals and that is
also used in the manufacture of alcohol and glucose. No account,
however, is taken of this important coefficient in business
transactions, potatoes containing proportions of starch varying from
13 to 23 per cent. being sold at the same price. Nevertheless, it is
of the greatest interest to cultivators to make such measurements,
since, in order to increase the value of their product, they might
thereby be led to make a judicious selection in their planting.

[Illustration: THE FECULOMETER.]

Mr. A. Allard, starting from the fact that the richness in starch
increases along with the density, has constructed a simple apparatus
that gives both these data at once, with sufficient precision, and
without calculations, tables, etc. It is, upon the whole, a large
areometer with constant weight and variable volume that is plunged
into a cylindrical vessel 0.5 m. in depth and 0.3 m. in diameter,
filled with water. The instrument itself consists of three parts: (1)
A lower receptacle in which is placed a weight to assure the
equilibrium; (2) a central float into which is put a kilogramme of
very clean and very dry potatoes; and (3) a rod graduated for density
and feculometric richness. The deeper the apparatus sinks, the more
valuable is the potato. How much more?

The degree to which the rod sinks shows this. The same principle and
the same instrument might be applied to the determination of the
density of various agricultural products, such as beets, cider fruits,
grain, etc. It would suffice to graduate a special scale each time.

For each variation of a thousandth in density, the areometer sinks
about 5 millimeters--that is to say, it presents a sensitiveness that
is more than sufficient in practice.--Le Monde Illustré.

       *       *       *       *       *




THE COMING LIGHT.


There is no more eager contest than that which has been going on for
some time between gas and electricity. Which of these two systems of
lighting will triumph? Will electricity suppress gas, as gas has
dethroned the oil lamp? A few years ago, the answer to this question
would not have been doubtful, and it seemed as if gas in such contest
must play the role of the earthen pot against the iron one. At present
the case is otherwise.

The Auer burner has re-established the equilibrium, and the Denayrouse
burner is perhaps going to decide the fate of electricity.

As naturalists say, the function creates the organ, and it is truly
interesting to observe that in measure as the need of an intenser and
cheaper light grows with us, science makes it possible for us to
satisfy it by giving us new systems of lighting or by improving those
that we already have at our disposal.

What a cycle traversed in twenty years! What progress made! Let us
remember that the electric light scarcely became industrial until the
time of the Exposition (1878), and that the Auer burner obtained the
freedom of the city only five or six years ago. Is there any need of
recalling the advantages of these two lights? In the first, a feeble
disengagement of caloric, automatic lighting and a steadier light; in
the second, a better utilization of the gas, which gives more light
and less heat.

A description of the Auer burner will not be expected from us. It is
now so widely employed as to render a new description useless. As an
offset we think that our readers will be more interested in a
description of the Denayrouse burner, the industrial application of
which has but just begun. This burner has been constructed in view of
the best possible utilization of the gas, in approaching a complete
theoretical combustion. In order that it may give its entire
illuminating power, gas, as we know, must be burned in five and a half
times its volume of air. In the Denayrouse burner the gas burns in
four and four-tenths its volume of air. The result reached is,
consequently, very appreciable.

[Illustration: SECTION OF THE LAMP.
A, entrance for the air; G, entrance for the gas; V, mixer; M,
electric motor.]

The apparatus consists essentially of a bronze or brass box in which
revolves a fan keyed upon an axle that passes through the box. The
axle is revolved by means of a small electro-magnetic machine mounted
upon one of the external sides of the box. The motor may also be a
hydraulic or compressed air one. Upon the axle is arranged a speed
regulator. The air enters at the bottom of the box and the gas at the
center. The exit of the mixture takes place through a chimney arranged
at the top and to which is fixed a luminous mantle. The apparatus
operates as follows: The motor causes the fan to make about 1,200
revolutions a minute. There is thus formed a strong draught of air,
which mixes with the gas that enters at the side. The ignition occurs
at the upper aperture of the chimney.

Although in this competition of gas and electricity the intensity of
the light and, its quality are important factors, it is certain that
what will decide the victory will be the price. This is why we are
going to establish the net cost of the different lights; for, although
up to the present the contest has seemed to be limited to gas and
electricity (oil and kerosene not being capable of having any other
pretension than to preserve their position), a new
competitor--acetylene--will perhaps soon put gas manufacturers and
electricians in accord, to the great benefit of the public, by
furnishing a brilliant light at a price that defies competition.

[Illustration: THE DENAYROUSE LAMP.]

In all systems of lighting, save electricity, the unit of light is the
carcel. This represents the light produced for one hour by 10 wax
candles, or, better still, it is the illuminating power given by the
combustion of 42 grammes of pure colza oil for one hour in what is
called a carcel lamp.

In electricity we count by watts. The watt, like the kilogrammeter, of
which it represents nearly a tenth, is not a unit of light, but a unit
of energy. What is called a kilogrammeter is the force capable of
lifting 1 kilogramme to 1 meter in height during 1 second. Further
along we shall estimate the watts in carcels.

This stated, let us ascertain the net cost of the unit of light in
each system of lighting. We shall take as a basis the Paris prices,
which are generally higher than those of other countries, owing to
taxes, and shall confine our researches to the eight following
systems:

Electricity (incandescent and arc lamps), gas (butterfly, Auer and
Denayrouse burners), lamp oil, kerosene and acetylene.

1. Oil Lamp.--This method of lighting has become more and more
neglected because it is the most troublesome. The mean price of the
kilo is 1.6 francs. As the carcel hour consumes 42 grammes, it
consequently amounts to 0.06, say 6 centimes.

2. The Incandescent Lamp.--In the scale of prices one of the oldest
processes of lighting is closely followed by one of the most
recent--the incandescent lamp. We shall base our calculations upon the
Edison 16 candle electric lamp, which is the one most widely used. In
this it takes 35 watts to obtain a carcel. As the hectowatt, the mean
price of which is 15 centimes, gives approximately 3 carcels, the
price of the carcel will, consequently, be 5 centimes.

3. Gas.--Gas, with the butterfly burner, burns from 125 to 130 liters
to furnish the carcel. As the price of a cubic meter is 30 centimes,
the carcel will cost 0.39, that is to say, 4 centimes.

4. Kerosene, the decline of which is perhaps beginning, costs about
0.75 centime per kilo. The consumption per carcel is nearly 40
grammes. It amounts, therefore, to 3 centimes.

5. The arc lamp is of very varied model. We shall take as a type those
used for lighting the large boulevards. They are of 8 amperes and 50
volts; that is to say, of 4 hectowatts, and are presumed to give an
illuminating power of 300 carcels. The carcel is consequently obtained
with 13 watts and its net cost is 0.0195, or, approximately, 2
centimes.

6. Acetylene.--This new system of lighting has hardly as yet made its
exit from the laboratory. So we must not be greatly astonished at the
variations in the price at which it is claimed that it can be obtained
on the two sides of the Atlantic. As a kilo of carbide of calcium
gives 300 liters of acetylene, and as the minimum price of the carbide
is 40 centimes per kilo in France, a cubic meter of the gas costs 1.35
franc. As it requires about 7.5 liters to give the carcel, the latter
will consequently amount to 0.01; say 1 centime.

7. The Denayrouse Burner.--This burns nearly 300 liters of gas to
produce 30 carcels, normally. As the photometric experiments are
recent, let us suppose that it gives but 25 carcels. As 300 liters of
gas represent an approximate expense of 10 centimes, we shall obtain
the carcel at the price of 0.004, or at less than half a centime.

8. The Auer Burner.--This burns nearly 115 liters of gas to produce 5
carcels. The expense per carcel, with the cubic meter of gas at 30
centimes, is therefore 0.0069; say 0.7 of a centime.

Finally, in the United States, thanks to particularly favorable
hydraulic installations, it is claimed that it is possible to produce
acetylene at a very low price, say at 33 centimes per cubic meter.
Under such conditions, the carcel would cost no more than 0.0025, say
¼ of a centime. It seems, however, that these are hypotheses as yet.
If they chanced to be realized, it is certain that acetylene would be
the light of the future; but those who are best informed in the matter
assert that they never will be realized.

In order to establish still more accurately the net cost of each of
these systems of lighting, it is necessary to take into account the
wear of the mantles of the incandescent lamps and the carbons of the
arc ones. As regards these latter, it is customary to estimate the
wear of the carbons at 8 centimeters an hour.

As for the mantles, we shall base our calculations upon the data
furnished by those interested; say 1,000 hours for the Edison lamp,
1,200 for the Auer burner and 400 hours for the Denayrouse burner. It
must be remarked that in practice such duration generally drops to a
half. The price of the mantles in these different systems is
approximately 2.5 francs.

1. As the Edison 16 candle lamp gives 1.6 carcels and its filament
burns 1,000 hours, the wear will increase the price of the carcel by
0.0015.

2. As the Auer burner gives 5 carcels and its mantle burns 1,200
hours, the wear will increase the price of the carcel by 0.0004.

3. As the Denayrouse burner gives 25 parcels, and its mantle burns but
400 hours, the wear will increase the price of the carcel by 0.0002.

Finally, if we compare the butterfly, Auer and Denayrouse burners with
each other, in taking into account the cost of replacing the mantles
of the two latter and the actuating of the Denayrouse burner, we find
the following figures per carcel hour:

  Butterfly burner, consumption                   0.04
                /consumption                      0.0069
  Auer burner,  \wear of mantle                   0.0004
                       /consumption               0.04
  Denayrouse burner,  { wear of mantle            0.0002
                       \expense of motor          0.0003
  Say 4 centimes per carcel hour    Butterfly burner.
     0.7    "          "     "      Auer       "
     4.5    "          "     "      Denayrouse "

For the same sum, the Auer burner, therefore, burns six times more and
the Denayrouse nine times more than the butterfly. These figures may
give an idea of the surprising intensity of the Denayrouse light.

Upon the whole, if the experiments that are being made publicly at
this moment confirm the data of the laboratory, the Denayrouse burner
will be destined to play a considerable role in the lighting of public
gardens, streets and buildings, for the very intensity of the light
that it gives renders it unfitted for private use. Moreover, it must
not be forgotten that it requires a motor to actuate its fan, and
everyone has not the necessary motive power in his house.

This new burner will likewise prove very valuable for the righting of
theaters.--L'Illustration.

       *       *       *       *       *




AN AIR BATH.

By J.H. COSTE.


This has been found useful for drying substances at temperatures above
100° C. It is usually difficult to obtain a temperature much above,
say, 120° in the ordinary air oven without using a large burner, which
is generally difficult to regulate. The temperature also varies
considerably at different heights in the oven. If the substance is
attacked by air at high temperatures or gives off other substances
than water, an estimation of the water is difficult.

[Illustration: Air Bath Apparatus]

The apparatus figured--which is made from a square "tin" or copper
box, with a lid perforated at the top to take a thermometer (T), the
bulb of which is level with the tubes (A and B) passing through the
sides of the box--is heated by an Argand burner and supported on a
retort stand. Dry air (or other gas) passes through the tube, B, where
it undergoes a preliminary heating, and then through the drying tube,
A. The substance to be dried is placed in a porcelain boat, or in a
tube passing through the cork of A (by the latter means precipitates
on filter tubes can be dried). It is usually sufficient to estimate
the loss in weight of the substance in the boat; but, if necessary,
drying tubes can be used to collect the water, or special absorbing
apparatus for other volatile substances.

A temperature of over 200° C. can be easily obtained with an ordinary
Argand flame and maintained fairly constant. When a thermometer was
placed inside as well as one outside the drying tube, it was found
that the temperatures only differed by a few degrees when a water pump
was drawing air through the system at the rate of about 8 liters per
hour. If this bath is protected from draught, any temperature can be
maintained within a few degrees easily.--Journal of the Society of
Chemical Industry.

       *       *       *       *       *




FIREDAMP TESTING STATION AT MARCHIENNE-AU-PONT.[1]

    [Footnote 1: H. Schmerber, Genie Civil, xxix, No. 11.--From the
    Colliery Guardian.]


In a previous paper[2] a description was given of the experimental
gallery at the St. William pit of the Kaiser-Ferdinands-Nordbahn
Colliery at Mahrisch-Ostrau (Moravia). In the present article a
similar experimental station, designed for the same purpose, but
presenting certain considerable advantages on the score of economy by
reason of the moderate expense of its installation, will be described.

    [Footnote 2: Reproduced in the Colliery Guardian, vol. lxxi,
    p. 317.]

Some few years ago the Société des Explosifs Favier obtained
permission from the proprietors of the Marchienne-au-Pont, near
Charleroi, Belgium, to construct there an experimental station for
testing the explosives manufactured by the company. Though of but
modest proportions, this station is well designed, and many valuable
researches and tests have been made on the explosives used in the
fiery pits of Belgium, thanks to which investigations one is able to
readily determine in a practical manner the degree of security offered
by any explosive intended for use in pits containing coal-dust in
suspension or firedamp.

In order to avoid the expense of constructing a large gallery above
ground, recourse was had to the cylindrical shell of a disused boiler
of large dimensions--some 5 m. in length by 1½ m. internal
diameter--one end of which was taken out, and the shell made to do
duty for a testing gallery. With this object it was mounted on two
settings of brickwork (Fig. 2), and the further end backed by a brick
wall of very substantial construction, being 1½ m. thick and 2 m. in
height, and forming the base of a high bank of earth. The boiler, as
may be seen in Figs. 1 and 2, was let into the ground a little, in
order that in case of an explosion there might be less chance of the
debris being projected to a distance. On one side the boiler was
pierced by six rectangular openings 20 cm. in height fitted with thick
glass panes in caoutchouc frames, to prevent their becoming fractured
by the aerial vibrations resulting from explosions. These windows
enable the operators to observe the phenomena occurring within the
chamber at the moment the explosion is produced. At the top of the
boiler, two circular apertures, each 50 cm. diameter, were made for
the purpose of acting as safety valves. By means of two rabbets, one
fixed at the open end of the gallery and the other in the center, the
testing chamber could be made either large or small by means of paper
disks pasted on to the first or second rabbet. The capacity of the
large chamber was double that of the smaller one, and the cubical area
of each was known beforehand.

[Illustration: FIG. 1, FIG. 2, and FIG. 3. Firedamp Testing Station]

In the backing wall was fitted a large mortar of cast steel, which in
carrying out the tests served to replace the borehole used in actual
mining operations. A pipe for conveying the gas and another for steam
were laid on the floor of the chamber, the latter for heating
purposes, in order to ascertain whether, in certain cases, an increase
in temperature exerts any sensible influence on the inflammability of
the explosive mixture. The temperature of the chamber is read off from
a thermometer placed at the top of the boiler, its position being
indicated by T in Fig. 2.

In view of the possibility of the boiler, notwithstanding its
strength, bursting, in the event of a violent explosion of the gas, it
became necessary to make special arrangements for allowing the
operators to observe everything occurring in the testing chamber
without being themselves exposed to the consequences of any accident
that might ensue. A special shelter was, therefore, erected for
occupation by the operators at the moment of the explosion. This
shelter, at about a dozen yards away from the boiler, consisted of a
chamber protected on the side next the gallery by a stout bank of
earth, in which a longitudinal aperture was provided (by means of a
lining of boards) at about the height of the face, through which the
operators could observe the progress of the tests, without danger. It
may be stated, however, that hitherto no accident has occurred, the
boiler effectually resisting the force of the explosions. The chamber
of shelter likewise contained the gasometer for regulating the supply
of gas to the testing apparatus, and the electrical machine for firing
the cartridges under test.

There being no continuous current of firedamp at disposal, use was
made of illuminating gas in preparing the explosive mixtures for the
tests. The borehole is charged with the explosive to be fired, and the
temperature is regulated by means of the steam pipe. The entrance of
the chamber and the two safety apertures in the roof having been
closed by disks of paper fastened by paste, the gas is turned on until
the desired percentage, has been introduced; the mixture of the air
and gas takes merely a short time to effect by diffusion, the
difference in density causing the gas to rise on issuing from the jet,
which is on the floor of the chamber. The detonating cap is then
ignited by the passage of the electric current and the shot fired. The
operator, placed in his shelter, can observe, by means of the small
lateral windows, whether any flame is produced, and indeed, a little
experience will enable him to determine by the sound alone, whether an
explosion has ignited the mixture or not.

Fig. 1 is a front view of the testing chamber with transverse section
of the shelter. Fig. 2 is a longitudinal section of the chamber along
CD, and Fig. 3 a view, half in plan, half in section, along AB. The
following are the references: M, backing wall; C, boiler; G, gas pipe;
V, steam pipe; M, mortar; E, electric wires; A, shelter; RG,
gasometer; ME, electrical machine; R', protective bank; R", backing of
earth; R, glazed windows; S, apertures serving as valves; T,
thermometer.

       *       *       *       *       *




PHOTOGRAPHY FOR CHEMISTS.

LANTERN SLIDES BY REDUCTION.


When a negative happens to be of larger size than a quarter plate, it
rarely happens that we can print a small portion by contact on a
lantern plate without spoiling the composition of the picture. This is
assuming, of course, that the operator has composed a picture and not
put his camera down anywhere. There is no great difficulty in making
lantern slides by reduction; the exposure is the only bugbear, as
usual.

There are two distinct methods of reduction: (1) daylight; (2)
artificial light. There is nothing to choose between them, and the
question of time and opportunity must decide which is to be adopted.
The apparatus required is not expensive. It can be made in odd moments
for a few pence, and is applicable to day and artificial light. It
consists of a printing frame the size of the large negative, four
pieces of bamboo a quarter of an inch in diameter, some black twill,
the ordinary camera and lens, and a carrier to take lantern plates 3¼
X 3¼ inches.

The negative is placed in the printing frame upside down and kept in
position by four little slips of wood, or better still, a frame such
as the gold slip used in picture frames, which will fit tightly into
the frame and hold the negative securely. Of course, brads may be
driven into two sides of the frame and the negative slipped behind
them, but in this case it is necessary to safe edge the negative. This
is done by cutting strips of tinfoil just wide enough to cover the
rabbet of the negative so that no clear glass can be seen; these
should be pasted and stuck on the glass of negative round the four
sides. The strips of bamboo are either nailed to the printing frame or
merely fastened together by stout copper wire, the shape being exactly
that of the printing frame. The other end of the bamboos are tied with
stout string to a piece of cardboard tube, postal tube, which slips
over the lens. The length of the bamboos depends upon the focus of the
lens and the amount of reduction. It will sometimes be found
convenient to have the bamboo in two lengths; thus, supposing we want
as a general rule 36 inches, two pieces, 24 inches each, should be
obtained, and by fastening these together in the middle by two loose
rings of copper wire we can extend them to 48 inches or reduce them to
24 inches.

The black twill or the focusing cloth (or even a dark table cloth may
be used) must also depend for its size on the length of bamboo, but
sufficient should be obtained to completely cover over the space
between lens and negative, and hang down on each side.

Of course, two laths of wood can be used, merely resting them on the
top of printing frame and camera, but the other plan is preferable,
the arrangement being more complete and adaptable to both day and
artificial light, and also more rigid, especially when the camera is
sloped toward the sky.

The ordinary camera may be used, but a carrier to take lantern plates
must be used in the dark slide. The ordinary lens may be used unless
of inordinately long focus, when it becomes inconvenient on account of
the great distance between negative and lens. To find the required
distance there is a simple rule, which is as follows:

(a) Divide the longer base of the plate by the longer base of the
image required, to the quotient add 1, and multiply by the focus of
lens used; the result will be the distance between negative and lens.

(b) Divide the distance found as above by the quotient obtained in the
first rule, and the result will be the distance between lens and
plate.

Example.--What are the relative distances in reducing a whole plate
negative, 8½ X 6½ inches, to lantern, size with an 8 inch focus lens?

Now that the whole of the lantern plate is not used, we reckon that 3
inches is all that can be used, because of the mask, hence:

  (a) 8½ ÷ 3 = 17/6 = the amount of reduction.
      17/6 + 1 × 8 = 23/6 × 8 = 30-2/3 inches.
  (b) 30-2/3 ÷ 17/6 = 11 inches (practically).

Therefore, if we place our lens about 30 inches from the negative and
rack the camera out to about 11 inches, we shall have an image on the
ground glass which merely requires a little adjustment of the camera
screw to be sharp and of the right size. In focusing, it is always
advisable to temporarily affix to the outside of the focusing screen a
square mark, this being, of course, accurately placed as regards the
center of the screen, and to use a focusing magnifier to obtain
critical sharpness.

Having satisfactorily arranged our image as regards composition by
shifting the camera nearer to or farther from the negative--because it
will be obvious that the nearer the lens to the negative, the less of
the negative we shall include, and vice versa--we fill our dark slide
and are ready for exposure.

For daylight work the arrangement of frame and camera should be placed
near a window, and if anything but sky is seen opposite the negative,
place outside the window a large sheet of white cardboard at an angle
of 45°. This will reflect equal skylight through all parts of the
negative. Now cover over the space between negative and lens, insert
your dark slide, in front of the negative place an opaque card, draw
the shutter of the dark slide, and remove the opaque card from
negative and expose.

Very little assistance can really be given as to exposure, but with a
negative of average density, which will give a good silver print, and
using a lens working at F/11 and a Mawson lantern plate at midday in
May, ten seconds will give a good black slide.

There is but one little point that has been missed--the diaphragm;
always use the largest diaphragm which will give satisfactory
definition, this will usually be F/11 or F/16.

Be very careful while exposing not to shake the camera--it is quite
sufficient for anyone weighing about eleven or twelve stones to walk
across the room to give double outlines.

Daylight is not a constant quantity, and although visually the same on
two different days, the actinic power of the light varies enormously;
therefore we prefer artificial light.

Precisely the same apparatus can be used for artificial light with one
or two additions. In some such arrangement in use the printing frame
containing the negative is fastened to the side of a cube sugar box in
which a hole is cut.

Opposite to the negative on the other side of the box is placed a
sheet of white cardboard bent slightly to the arc of a circle. The
lights, etc.--two incandescent gas burners do well with tin reflectors
behind them--are placed one on each side of the negative inside the
box, so that the light is reflected on to the card and thence on to
the negative, and no direct light reaches the negative. Absolutely
even illumination, even of a large negative, is thus obtained, and the
exposure, using the same conditions as stated for daylight, is only
twenty seconds.

Of course, the light may be placed directly behind the negative, but
in this case a diffuser, such as a sheet of opal glass, must be placed
between light and negative, and even then, unless great care is
exercised, uneven illumination of the negative and consequent unequal
density of the slide must ensue.

We may use magnesium ribbon, and a diffuser of opal is then necessary,
and the ribbon must be kept in motion the whole of the time. Magnesium
is objectionable because the particles of magnesia form a voluminous
cloud, which tastes and smells unpleasantly and settles down on
everything. Still, for those who wish to work with this substance,
about 18 inches burnt close to the opal and moved about all over it
will be about sufficient to obtain good results under above mentioned
conditions. An ordinary oil lamp or gas may also be used, provided the
light is diffused.

Only the bromide lantern plates are suitable for reduction, the
exposure, especially with the chloride emulsions, being so long as to
place them out of court. The chloro-bromide may be used for daylight
and magnesium ribbon.

After development and fixing, which may be performed in the developers
recommended by the makers of the plates used, the lantern slide must
be well washed and cleared in an alum and acid bath, then again well
washed and finally given a gentle rub with a piece of cotton wool
under the tap, and set up to dry.

The finishing off of a slide is not a difficult matter, but one which
wants doing properly. Place the slide film downward upon a piece of
white paper, and with a box of assorted masks try various shapes till
the one most suitable to the picture is found, and frequently a mask
with a comparatively small opening will give the best results
pictorially. Having found the most suitable mask, lay it on the slide,
on the top of this a cover glass well cleaned, and it is ready for
binding. Binding strips can be purchased commercially in long strips,
but personally we prefer to use 3¼ strips, as somewhat easier to
apply. Wet 3¼ in. of the strip, lay it flat on the table, pick up the
slide and cover glass and adjust on the wetted slip so that there is
an equal width on either side; now press the glasses firmly on to the
strip and lift from the table and with a handkerchief or soft duster
wipe the strip on to the glass of the slide and cover, taking care
that these do not slip; when it adheres firmly, that is, does not
immediately rise up, lay the whole on one side and go on with next
slide; by the time half a dozen have been thus treated a second side
may be stuck down, and thus with the third and fourth. By working in
this way a far neater and safer job is made of it than if all four
sides are bound at once.

The final operation is tilting and spotting. There are several makes
of masks on the market on which a blank white space is left for the
title, and it is just as well to write the title on the mask, as it is
then protected by the cover glass. If the ordinary masks are used,
Chinese white may be used for the titles.

"Spotting" the slides is affixing to them two marks, by means of which
the lantern operator can tell which side is to be placed next the
lantern, and these marks usually take the form of two white circles.
Such "spots" can be bought commercially already gummed, or postage
stamp edging may be used.

A few minutes' thought will show that the projecting lens of the
lantern will reverse an image just as the lens of the camera does, so
that we must insert the slide into the lantern carrier upside down and
wrong way round, and as the spots are used to indicate this, they must
be placed at the top of the slide, when the view appears to us as we
saw it in nature. If it be a subject with lettering in it, the spots
must be placed at the top of the slide, when we can read the lettering
the right way as the slide is looked at against a piece of white
paper.

       *       *       *       *       *




PRECIOUS STONES.[1]

    [Footnote 1: Lecture delivered before the Society of Arts, from
    the Journal of the Society.]

By Prof. HENRY A. MIERS, M.A., F.R.S.

LECTURE I.


The object which I have proposed to myself in these two lectures is to
consider, not the history nor the artistic interest of precious
stones, but simply some of their curious properties. In the first
place, then, I will ask you to accompany me in the inquiry as to those
characters of precious stones to which they owe their beauty and their
value, and next to pursue the inquiry a little farther and to see how,
by means of these characters, the same stones may be studied, and
hence, also, identified with accuracy.

From the earliest times certain minerals, which are conspicuous for
their beauty, have been prized for decorative purposes; the brilliant
green hue of malachite, the deep blue of lapis lazuli and the rich
color of red jasper would naturally attract early attention. But these
particular minerals are not numbered among the true precious stones;
they do not possess the remarkable qualities which endow the diamond,
the ruby or the topaz with their peculiar attractiveness. The two
essential qualities, namely, brilliancy and hardness, are only
possessed by certain rare minerals; a brilliancy which makes them
unrivaled for ornamental purposes and a hardness which protects them
from wear and tear and makes them practically indestructible.

It is difficult in a town like London, where every jeweler's shop is
ablaze with diamonds, to realize that large and good stones possessing
these qualities are so rare; that thousands of natives are toiling in
the river beds of India, Burma and Ceylon washing out from the gravel
or the sand the little blue and red pebbles which are to be converted
by the lapidary's art into brilliant jewels of sapphire and ruby. Even
in that wonderful pit at Kimberley, where half the diamonds of the
world seem to have been crowded together for the use of man, although,
perhaps, ten tons of diamonds, worth more than £50,000,000, have been
extracted in twenty-five years, yet those which weigh more than an
ounce each may be counted on the fingers.

It is in the qualities of hardness and brilliancy that such minerals
as malachite and lapis lazuli fail; owing to their comparative
softness, they would not, if cut and polished, possess the sharp edges
and brilliant surface of the emerald or sapphire, and would soon
become dull and rounded by friction, even by the friction of ordinary
dust. Again, since they are opaque, they can never flash like the
sapphire or the emerald; and yet it is quite a mistake to suppose that
the necessary qualities are confined to those few stones which are
familiar to everyone, such as the diamond, ruby, sapphire, emerald,
garnet and amethyst. There are many others, though they are not so
well known. I think we may fairly assert that such minerals as
tourmaline, jargoon, peridote, spinel and chrysoberyl, though their
names may be familiar, are not stones which would be recognized by any
but those who are in some sense experts; while other minerals, such as
sphene, andalusite, axinite, idocrase and diopside, are possibly
almost unknown to most people, even by reputation. Yet all these
minerals possess qualities of transparency, hardness and beauty of
color which render them extraordinarily interesting and attractive as
precious stones. (A number of faceted stones cut from the less known
minerals were thrown upon the screen by reflected light.)

Take first the hardness. A few years ago the hardness of stones was a
very important character in the eyes of the mineralogist; it was one
of the characters by which they were invariably identified, and a
distinguished German mineralogist drew up a table by means of which
the hardness of minerals can be compared. Any stone is said to be
harder than the minerals of this scale which it can scratch, and
softer than those by which it can be scratched. In the right hand
column the gem stones are arranged according to their hardness.

MOHS' SCALE OF HARDNESS.

  1. Talc.
  2. Gypsum.
  3. Calcite.
  4. Fluor.
  5. Apatite.     / Sphene.
                  \ Opal.
  6. Feldspar.    / Diopside.
                  \ Moonstone.
                  / Epidote.
                 |  Idocrase.
                 |  Peridote.
                  \ Axinite.
  7. Quartz.      / Quartz.
                 |  Tourmaline.
                 |  Cordierite.
                  \ Garnet.
                  / Andalusite.
                 |  Zircon.
                 |  Emerald.
                  \ Phenacite.
  8. Topaz.       / Spinel.
                 |  Topaz.
                  \ Chrysoberyl.
  9. Corundum.    / Ruby.
                  \ Sapphire.
  10. Diamond.      Diamond.

Among precious stones diamond stands out pre-eminent as the hardest of
all known substances. Ruby and sapphire are scratched by diamond
alone, while chrysoberyl, topaz and spinel scratch all the remaining
stones, although they do themselves yield to the scratch of ruby and
sapphire. The hardness is a character still generally utilized by the
expert when he is in doubt; in experienced hands it has some value. By
long practice it is possible to form a very close estimate of the
hardness of a given stone, and that often, not by the scratch of the
other minerals in the scale, but by the feel of the stone against a
file; the resistance offered by the stone to the file is taken as a
measure of its hardness. It is not a character capable of any accurate
measurement, neither is it to be recommended for use by inexperienced
persons.

I hope to show, as I go on, that we have now accurate methods of
testing at our disposal which render the trial of hardness quite
unnecessary. But, none the less, the character is one of great
importance, as investing the stone with durability. All the precious
stones, except moonstone, opal and sphene, have at least the hardness
of quartz, and can barely be scratched by metals, even by hard steel.

[Illustration: FIG. 1.--TOTAL REFLECTION OF LIGHT IN GLASS.]

Take next the quality of brilliancy. This depends upon two
things--first, the manner in which rays of light are affected when
they enter or leave the stone, and, secondly, the manner in which this
action can be intensified by the art of the lapidary.

When light passes from one transparent substance to another it is bent
or refracted, as every one knows from the bent appearance of a stick
plunged into water. Consider, now, a ray of light falling upon the
surface of a transparent stone; a portion of the light is reflected,
but a portion enters the stone. In passing from air into the stone it
is refracted inward. When, on the other hand, it passes from a
transparent stone into air, its course is reversed and the emerging
ray is refracted outward or toward the surface. It is, however, with
the emerging as with the entering light, the beam is subdivided, only
a portion is refracted out, another portion of the light is reflected
within the stone.

Consider next successive rays within a piece of glass or a stone which
are about to emerge with different inclinations. (See Fig. 1.) As
their course approaches more nearly to the surface, so will the
emerging rays issue more nearly along the surface of the stone; but
the obliquity of the emerging rays increases much more rapidly than
that of the internal rays, until for one ray in the series the
direction of the light (C in the figure) refracted out coincides with
that surface. What, then, will happen to the light within the stone,
which falls still more obliquely? It cannot be refracted out, and, as
a fact, it is entirely reflected within the stone. Imagine, then, how
much greater is the brilliancy of the beam of light, c, e, d, which is
completely reflected, than that of the intermediate portion of the
reflected light, a, b, c, which has lost a large part of its rays by
refraction. The difference is easily seen by looking at a glass of
water held above the head; the brilliant silvery appearance of the
surface, when viewed obliquely, is due to total reflection. The light,
c, d, e, is said to have been totally reflected; and half the angle
between C and c is called the "angle of total reflection." This angle
depends upon the refractive power of the stone. The angle of total
reflection for diamond is about 25°; in no other stone is the
corresponding angle less than 30°; for most of them it is much
greater; while for heavy glass it is about 40°. Light striking the
internal surface more obliquely is reflected without losing any of its
rays by refraction.

[Illustration: FIG. 2.--TOTAL REFLECTION OF LIGHT WITHIN A BRILLIANT.]

It is very clear, then, that of the light traveling in directions
within a diamond, a far larger proportion is internally reflected than
is the case with any other stone. We shall see presently that it is
this property which gives the diamond its consummate brilliancy.

Another effect produced by refraction is, as every one knows, the
separation of ordinary light into rays of different colors--it is seen
in any prism of glass. This property is known as the "dispersion" of
light; and a stone which possesses great dispersion will exhibit a
beautiful play of spectral colors--will exhibit a high degree of what
is called fire. In this respect again the diamond is pre-eminent; its
dispersion is nearly twice as great as that of other stones.

All these optical properties are beautifully shown by those unworked
jewels of which the smooth facets have been produced by nature; I mean
the crystals of the various minerals. The beauty of natural crystals
of transparent minerals is largely due to the optical effects which I
have just been describing.

The beautiful specimens of rock crystal, calc spar, topaz, emerald,
and other stones which adorn mineral collections are sufficient
evidence of these properties. But it is very certain that natural
crystals, although they possess a beauty of form which is all their
own, are not by a long way so brilliant as the faceted stones which
are cut from them by the art of the lapidary; that a natural diamond
is not so lustrous as a faceted brilliant.

In fact, many of the finest gem stones present a very mean and sordid
aspect before they have passed through the hands of the lapidary; one
has only to compare the dull and unattractive appearance of a parcel
of rough rubies, sapphires or rough diamonds with the finished jewels
displayed in the jewelers' windows to see how much these owe to the
lapidary's art.

In recutting the Koh-i-noor it was thought advisable to spend £8,000
on the process and to reduce its weight from 186 to 106 carats. When
the great Pitt diamond was cut, its weight was reduced from 410 carats
to 137; and the fragments and dust removed were valued at £8,000; but
the extent to which the stone was improved is indicated in the fact
that having been purchased for £20,000, it was after cutting sold for
£135,000.

To understand how the cutting of a precious stone adds to its
brilliancy, we have only to trace the course of the rays within the
stone, and consider how it can best be faceted in order that the light
which enters in various directions on the upper side, or crown, may be
reflected internally from facet to facet on the under side of the
stone with as little loss as possible, and may be thrown out from the
front of the stone. For this purpose the facets must be so arranged
that as much of the light as possible within the crystal shall meet
the facets at an inclination exceeding the angle of total reflection.
A brilliant with its 58 facets is one of the forms which experience
has shown to be best adapted for the purpose. How little of the light
gets through a stone so faceted, and, therefore, how much of it is
totally reflected internally, is easily shown by holding the stone in
a strong beam of light; first so that the light is so reflected, and
then so that the light shall, if possible, be transmitted. In the
latter case, the stone merely throws a dark shadow, indicating that
little light, if any, has passed through it.

A faceted stone is always cut from a single crystal, and not from an
ordinary lump of the mineral, which is generally a mass of crystals.
The chief reason why jewels are cut from natural crystals is that
these, by virtue of their crystalline nature, are remarkably
homogeneous, and therefore clear and limpid when free from cracks and
flaws. A stone which is not homogeneous can never have the purity and
limpid brilliancy of a single crystal, for at every point of contact
of one part with another reflection takes place. Among minerals used
as precious stones which are not crystals may be mentioned the opal.
The opal probably owes its peculiar beauty to the very fact that it is
filled with minute cracks or cavities, each of which contributes some
tint of color by reason of its extreme thinness, just as the colors of
the soap bubble are due to the thinness of its film.

Or take the agate. Here the stone consists of layers of different
materials differently colored. Its beauty is of a different nature
from that of clear crystals, which it can never rival in brilliancy.
Stones like the agate are generally classed apart as semi-precious
stones, and their interest depends upon beauty of structure or color,
or possibly to a large extent upon their rarity. The turquois, for
example, is a very rare stone, which is apparently absolutely
uncrystallized, but possesses great beauty of color, and is therefore
much prized. The same is true of carnelian. On the present occasion we
are not concerned with those opaque or curiously structured minerals
whose beauty resides almost solely in their color.

Those who have had no practical acquaintance with minerals have little
idea how variable and accidental are their colors. They may scarcely
realize that the ruby and the sapphire are the same mineral, and that
this mineral also occurs, and is used in jewelry, absolutely
colorless, when it is known as lux sapphire, green as the so-called
Oriental emerald, and yellow as the so-called Oriental topaz; that
topaz itself may be yellow, brown, blue, or colorless; that zircons
range from colorless through almost all conceivable shades of brown
and green, and that even diamond has been found green, red and blue.

When we come to consider the properties by which precious stones are
recognized, I shall say little or nothing about color, for it is of
little value as a criterion. There are, for example, certain red
stones which the most skillful experts cannot by their color alone
refer with certainty to ruby, garnet or spinel. It might be expected
that a noteworthy difference in chemical composition would accompany
this difference of color, or that the pigment could be ascertained by
analysis. In reality this is scarcely ever the case. It is fairly
certain that the emerald owes its color to the presence of chromium,
but the variation in the analyses of precious stones cannot generally
be attributed to anything indicated by the variation of color.

The chemical composition, though of great general importance in
mineralogy, is of little practical value in the discrimination of
precious stones, since it is usually impossible to sacrifice a
sufficient quantity for chemical analysis. If we are dealing with a
faceted stone, not even the smallest portion can be utilized, for fear
of injuring it.

There is, however, one remarkable optical property, which is
ultimately related to the chemical composition. As is well known, many
substances possess the property of absorbing certain rays of light.
When the solar spectrum produced by admitting ordinary daylight
through a slit, and transmitting it through a prism, is passed through
the glowing vapor of certain substances, particular rays of light are
absorbed, and their absence from the emerging fight is manifested by
corresponding dark bands in the spectrum. The instrument by which the
observations are made is the spectroscope. It is well known to most
people that the solar spectrum itself contains certain dark bands of
this sort, which are produced by vapors that can be identified by the
position of the bands in the spectrum; and thus it is possible to
ascertain something regarding the chemical constitution of the sun and
certain of the heavenly bodies. Now, a precisely similar effect is
produced by certain elements if present in a mineral, by merely
transmitting the light through a piece of it. Thus, transparent
minerals which contain the rare element didymium betray the presence
of that element as soon as they are viewed through a spectroscope by
ordinary daylight; the spectrum is seen to be traversed by black bands
in the green, which are quite characteristic.

Among gem stones there are two which possess this curious property.
One is the variety of red garnet known as almandine, and the other is
the jargoon. The almandine produces characteristic bands in the green
and the jargoon in the red, green and blue portion of the spectrum. To
see these remarkable absorption spectra, to which attention was first
called, I think, by my friend, Prof. Church, it is not necessary to
look through the stone, it is quite sufficient to place it in a strong
light, and look at it through an ordinary pocket spectroscope; the
light which enters the instrument consists largely of rays which have
penetrated the stone, and been reflected from the facets at the back.
These rays produce the absorption spectrum. In this way we are enabled
to identify a jargoon or an almandine merely by looking at it. There
is no test so simple or so easy of application. It is curious that the
almandine, or iron aluminum garnet, is the only garnet which presents
an absorptive spectrum, and it is not yet certain to what element the
bands are due. In the case of jargoon, they are supposed to be caused
by the presence of some uranium compound in the mineral. All the
almandine garnets which I have examined, and nearly all the jargoons,
show these characteristic absorption spectra.

[Illustration: FIG. 3. Graph of Specific gravity vs Refractive index
of gems]

By way of summary, I have thought it desirable to indicate the general
characters of precious stones in a diagram, which exhibits some of
their relationships and also some of their differences in a graphic
manner.

Opal, which is a comparatively light mineral, has a low refractive
power; zircon or jargoon is a heavy mineral, and has a high refractive
power. Let now the refractive power of any mineral (as measured by its
refractive index for yellow light) be represented by a corresponding
length set off from left to right, and let its density (as measured by
its specific gravity) be represented by a corresponding length
measured downward. Fixing in this way a point corresponding to opal,
and another representing the character of zircon, draw a straight line
from the one to the other. It will then be found that the points
which, by their position on the diagram, represent the specific
gravity and refractive index of the various minerals will be very
nearly upon this line; that is to say, as the refractive index of
precious stones increases, so also does their density, and the two
increase together in a remarkably regular manner.

It appears from this table that those minerals which, by their high
refractive power, possess the greatest brilliancy, possess also the
highest specific gravity or weightiness; that the precious stones are
therefore all heavy minerals. There is also a rough general
correspondence between these characters and the hardness of the
stones; the brilliant heavy minerals are also generally speaking hard.

Two remarkable exceptions display themselves. Sphene lies far to the
right of the position which it should occupy according to its specific
gravity; it possesses an extraordinarily high refractive index, and
is, therefore, an extremely brilliant gem stone. On the other hand, a
glance at the scale of hardness shows that it is, unfortunately, one
of the softest of the possible gem stones, and that in this respect it
is not very well fitted for jewelry.

Diamond is still more remarkable; its refractive index places it at
the extreme right of the diagram, with a refractive power, and
therefore a brilliancy, greater than that of any other stone; at the
same time its hardness exceeds that of any mineral, and this
combination of qualities renders it the chief among gem stones,
unequaled for brilliancy and durability, although not a heavy mineral.
Moreover, in dispersion, and therefore in fire, it stands alone.
Minerals which are heavier than zircon, such as the metallic sulphides
and iron glance, are unsuitable for gem stones, since they are nearly
opaque, but they follow the same law, and possess a refractive power
still greater than that of zircon or even diamond.

There is one other stone which is exceptional, but in less degree and
in the other direction, namely, topaz, whose refractive index is not
1.7, as it should be by its position on the line due to the specific
gravity, but 1.62; the point corresponding to topaz must therefore be
placed a short distance to the left of the line. It is curious that
these three exceptional stones lie on the same horizonal line, having
all the same specific gravity, 3.5.

In mentioning the specific gravity I have introduced a property which
is not essential to win esteem for a precious stone, but one which is
of great value in its identification.

We have next then to consider those properties by which precious
stones may in practice be most readily recognized. The table shows
very clearly that specific gravity is one such property. The meaning
of specific gravity is easily explained. A piece of tourmaline of any
size weighs three times as much as an equal volume of pure water at 4°
C., the specific gravity of tourmaline is therefore said to be 3; a
piece of almandine garnet of any size weighs four times as much as an
equal volume of water under the same conditions, and the specific
gravity of garnet is therefore 4.

Now any substance immersed in water loses in weight by an amount
exactly equal to that of the water displaced. Hence, to ascertain the
specific gravity it is only necessary to suspend the stone by a fine
thread to the beam of a balance and weigh it first in air, and then
immersed in water. The first weighing gives the weight of the stone
itself, the difference between the first weighing and the second gives
the weight of the displaced water; hence the specific gravity is found
at once by dividing the weight of the stone by this difference. For
very small stones, where the weights concerned are slight, it is
necessary to use a refined chemical balance. But for ordinary stones a
well made Westphal balance is sufficient.

The Westphal balance is constructed on the principle of the common
steelyard. At one end of the beam is a counterweight, at the other end
the stone is suspended; the beam is divided into ten equal parts. A
weight can be suspended on the beam, and its action, of course, varies
with its position on the beam; at the tenth division from the center
it has a value ten times as great as at the first division.

The specific gravity is then found as follows: First, counterpoise the
counterweight. Let this require a weight, A, on the right hand side of
the beam. Next, find the weight necessary to restore equilibrium when
the stone is suspended from the beam. Let this be B. Then A-B is the
weight of the stone in air. Next raise the vessel of distilled water
below the stone until it is immersed. If C be the weight now required
to restore equilibrium, C-B is the loss of weight in water, and,
finally, the specific gravity is (A-B)/(C-B).

This process is known as "hydrostatic weighing," and can be applied to
any stone, except such as are very small. Great precautions must be
taken, in order to determine the specific gravity with accuracy.
Especially it is necessary to free the stone from all adhering bubbles
of air. For this reason the process of hydrostatic weighing is a
somewhat laborious one.

Now, in order to identify a mineral, it ought to be unnecessary to
determine exactly the specific gravity, provided that means can be
devised for showing that its specific gravity is the same as that of
some known substance. For purposes of identification, a comparative
method is often quite as efficacious, and much more easy than actual
measurement. This may now be done by means of certain heavy liquids.

Wood floats in water because it is lighter than water; iron sinks
because it is heavier; but a substance which possessed exactly the
specific gravity of water would neither float nor sink, but would
remain suspended in the water like a balloon in midair. Taken, then, a
liquid which is heavy--the most convenient is methylene iodide, whose
specific gravity is 3.3--a fragment of zircon will sink in this, and a
fragment of tourmaline will float, but a fragment of the mineral
augite, whose specific gravity is also 3.3, will remain exactly
suspended.

This liquid, then, enables one to say with certainty whether a given
stone has a specific gravity greater or less than 3.3; in the one case
it will sink, in the other it will float.

But methylene iodide further possesses the valuable property of mixing
easily with benzene, which is a very light liquid. Every drop of
benzene added reduces the specific gravity of the mixture, which can
thus easily be made to range between that of chrysolite and that of
opal.

To identify any one of the stones which lie between those limits on
the diagram, it is only necessary to drop it into a test tube or small
vessel containing methylene iodide--the stone will float--benzene is
added drop by drop, the mixture being kept well stirred until a point
is reached at which the stone neither sinks nor floats. Then different
fragments of mineral possessing specific gravities between 3.3 and 2.5
are taken in order of increasing density and dropped into the liquid;
the stone under examination possesses a specific gravity between that
of the last which floated and the first which sinks, and the limits
may, if necessary, be further narrowed by comparing it with other
mineral fragments of known density intermediate between those two. One
great advantage of this method is that the size of the fragment does
not affect the result; a minute fragment only just large enough to be
visible is equally convenient; in fact, more convenient than a larger
one.

If a stone in the rough is under examination, a minute chip can easily
be taken from it, and used for the experiment in the most satisfactory
manner. The method is, moreover, extremely sensitive; a mere drop of
benzene added to a considerable volume of the liquid is sufficient to
send to the bottom a stone which was previously floating.

So much for stones whose density is less than that of chrysolite. As
regards the denser minerals, it was until a short time back impossible
to test them by any such method; they all sank in the heaviest liquid
available. But now, thanks to the fortunate discovery by Dr. Retgers
of the remarkable properties of thallium silver nitrate, all the known
gem stones may be distinguished by a similar process.

This salt, which may be prepared by fusing together in equal molecular
proportions nitrate of silver and nitrate of thallium, possesses the
remarkable property of fusing at a temperature far below that of
either of its constituents, and well below that of boiling water,
while at the same time the fused salt possesses a specific gravity
greater than that of zircon. The salt fuses at 75° C. to a clear
colorless liquid in which zircon just floats; it further possesses the
useful property of being miscible in all proportions with water, so
that the specific gravity can be reduced to any desired extent by
adding water, just as that of methylene iodide, was reduced by adding
benzene. The substance can be kept liquid by maintaining it at a
temperature above 75° C., and this may easily be done by immersing the
vessel in which it is contained in water heated to near the boiling
point.

In these two liquids then we have the means of producing a liquid of
any required density for the discrimination of gem stones, since we
can obtain from one or the other a liquid in which any precious stone
will be exactly suspended.

The nitrate might be used by itself to include the whole series, but
it is more convenient to use the methylene iodide when possible, both
because it can be employed at ordinary temperatures and because it is
cheaper than the nitrate.

Both substances darken on exposure to light, and should be both kept
and used in the dark as far as possible: they are easily freed from
the liquid employed to dilute them. The benzene readily evaporates
spontaneously from the methylene iodide, and the water can be driven
off from the diluted thallium silver nitrate by boiling.

(To be continued.)

       *       *       *       *       *




A RESEARCH ON THE LIQUEFACTION OF HELIUM.[1]

    [Footnote 1: Translated from the original paper, by Prof. K.
    Olszewski, in the Bulletin de l'Academie des Sciences de
    Cracovie for June, 1896, "Ein Versuch, das Helium zu
    verflunigen," by Morris Travers, and published in Nature.]


My experiments on the liquefaction of helium were carried out with a
sample of that gas, sent to me by Prof. Ramsay from London, in a
sealed glass tube holding about 140 c. cm. I take this opportunity of
rendering him my most sincere thanks. In his letter Prof. Ramsay
informed me that the gas had been obtained from the mineral clevite,
and that it was quite free from nitrogen and other impurities, which
could be removed by circulation over red hot magnesium, oxide of
copper, soda lime, and pentoxide of phosphorus. The density of the gas
was 2.133 and the ratio of its specific heats (Cp/Cv) 1.652, the
latter figure indicating that the molecule of helium was monatomic, as
had already been found to be the case with argon. Prof. Ramsay further
informed me that the gas was only very slightly soluble in water, 100
c. cm. of water dissolving scarcely 0.7 c. cm. of helium.

From the results of my earlier experiments I had been led to expect
that it would be only possible to liquefy helium at a very low
temperature; the small values obtained for the density and solubility
of the gas, together with the fact that its molecule is monatomic,
indicating a very low boiling point. For this reason I did not
consider it necessary to use liquid ethylene as a preliminary cooling
agent, but proceeded directly to conduct my experiments at the lowest
temperature that could be produced by means of liquid air. The
apparatus employed in these investigations is figured in the
accompanying diagram.

The helium was contained in the glass tube, c, of the Cailletet's
apparatus, C. The tube, c, reached to the bottom of a glass vessel, a,
which was intended to contain the liquid air. The vessel, a, was
surrounded by three glass cylinders, b, b' and b", closed at the
bottom and separated from one another. The outer vessel, b", was made
just large enough to fit into the brass collar, o, which supported the
lid, u, of the apparatus. The tube, a, fitted into an opening in the
center of the lid; the tube, t, connected with an apparatus delivering
liquid oxygen, passed through a hole on the right. The vessel, b, was
also connected with a mercury manometer and air pump by means of a T
tube, p, v, one arm of which passed through the third hole in the lid
of the apparatus. The tube, a, was closed by a stopper, through which
passed the tube, c, of the Cailletet's apparatus, a tube connected
with the drying apparatus, u, u', and one limb of a T tube, by means
of which the manometer and air pump could be put in connection with
the interior of the vessel. The lower part of the whole apparatus was
inclosed in a thick walled vessel, e, containing a layer of phosphorus
pentoxide.

By turning the valve, k, the vessel, b, could be partially filled with
liquid oxygen, which, under a pressure of 10 mm. of mercury, boiled at
about -210° C. Almost immediately the gaseous air began to condense
and collect in the tube, a; a supply of fresh air was constantly
maintained through the drying tubes, u and u', which were filled with
sulphuric acid and soda lime respectively. When the quantity of liquid
air ceased to increase, the tap on the U tube, u, was closed, the T
tube, p' v', was connected with the manometer and air pump, and the
liquid air was made to boil under a pressure of 10 mm. of mercury. In
order to protect the liquid air from its warmer surroundings, a very
thin, double wall tube, f, reaching to the level of the liquid in the
outer vessel, was placed inside the tube, a. When, as in some of my
experiments, liquid oxygen was used in the inner vessel, this part of
the apparatus was dispensed with.

[Illustration: Helium cooling apparatus]

Using the apparatus I have just described, I carried out two series of
experiments, in which liquid air and liquid oxygen were employed as
cooling agents. The tube of the Cailletet's apparatus was thoroughly
exhausted by means of a mercury pump, and then carefully filled with
dry helium. In the first series of experiments the helium, confined
under a pressure of 125 atmospheres, was cooled to the temperature of
oxygen boiling, first under atmospheric pressure (-182.5°), and then
under a pressure of 10 mm. of mercury (-210°). The helium did not
condense under these conditions, and even when, as in subsequent
experiments, I expanded the gas till the pressure fell to twenty
atmospheres, and in some cases to one atmosphere, I could not detect
the slightest indication that liquefaction had taken place. The first
time that I compressed the gas I had, indeed, noticed that a small
quantity of a white substance separated out and remained at the bottom
of the tube when the pressure was released. Possibly this may have
been due to the presence of a small trace of impurity in the helium,
but it could not have constituted more than 1 per cent. of the total
volume of the gas.

In the second series of experiments I employed liquid air, boiling
under a pressure of 10 mm. of mercury. The helium was first confined
under a pressure of 140 atmospheres, and then allowed to expand till
the pressure fell to twenty atmospheres, or, in some cases, to one
atmosphere. The results of these experiments were also negative, the
gas remained perfectly clear during the expansion, and not the
slightest trace of liquid could be detected. The boiling point of
liquid air was taken, from my previous determination, to be -220° C.
(Comptes Rendus, 1885, p. 238). This number cannot, however, be taken
as a constant, as the liquid air, boiling under reduced pressure,
becomes gradually poorer in nitrogen. Further, the quantity of
nitrogen lost by the liquid air on partial evaporation varies not only
with the rate of boiling, but even according to the manner in which it
has been liquefied.

If air, under high pressure, be cooled first to the temperature of
boiling ethylene, and then to -150° C., it liquefies, and, on reducing
the pressure slowly, liquid air is obtained boiling under atmospheric
pressure. During the process a considerable quantity of the liquid air
evaporates, and the proportion of nitrogen to oxygen in the remaining
liquid is less than in air liquefied under high pressure. If the
liquid air obtained by this process be made to boil under a pressure
of 10 mm. of mercury, the proportion of nitrogen in the mixture
continues to decrease, but, on account of the large quantity of oxygen
present, the liquid does not solidify, although its temperature is
some six degrees below the freezing point of nitrogen. When, as in
some of my former experiments, the air was liquefied under normal
pressure by means of liquid oxygen boiling under a pressure of 10 mm.
of mercury, the ratio of nitrogen to the oxygen in the liquid air was
the same as in the gaseous air from which it had been produced. The
liquid air, obtained by direct condensation at normal pressure,
appeared to lose oxygen and nitrogen with about equal rapidity, and at
the end of the experiment a considerable quantity of liquid nitrogen
remained behind in the apparatus. On reducing the pressure to 10 mm.
of mercury the nitrogen solidified. Prof. Dewar has stated that liquid
air solidifies as such, the solid product containing a slightly
smaller percentage of nitrogen than is present in the atmosphere. My
experiments have proved this statement to be incorrect; liquid oxygen
does not solidify even when boiling under a pressure of 2 mm. of
mercury.

After carrying these experiments to a successful conclusion, I found
that it was yet necessary to prove that, on reducing the vapor
pressure of boiling oxygen, to a minimum, no corresponding fall of
temperature takes place. The vessel, e, was partially filled with
liquid oxygen, and, by means of a small siphon, a small quantity of
the liquid was allowed to flow into the tube, a. The inner vessel, a,
was then connected with the air pump and manometer, and the pressure
was reduced to 2 mm. of mercury. The oxygen remained liquid and quite
clear. In a second experiment the temperature of the liquid oxygen,
boiling under 2 mm. of mercury pressure, was measured by means of a
thermometer. The temperature indicated lay above -220° C., a
temperature easily arrived at by means of liquid air. I, therefore,
concluded that liquid air was a much more efficient cooling agent than
liquid oxygen, and that it would be quite unnecessary to make further
experiments on the liquefaction of helium.

In every single instance I have obtained negative results, and, as far
as my experiments go, helium remains a permanent gas, and apparently
much more difficult to liquefy than even hydrogen. The small quantity
of the gas at my disposal, and, indeed, the extreme rarity of the
minerals from which it is obtained, compelled me to carry out my
investigation on a very small scale. Using a larger apparatus, and
working at a much higher pressure, I could have submitted the gas to
greater expansion. Further, I should have been able to measure the
temperature of the gas at the moment of expansion by means of a
platinum thermometer, as I did when working with hydrogen; but to make
such experiments I should have required 10, if not 100, liters of the
gas. As I was unable to determine the temperatures to which I cooled
the gas, by any experimental means, I have been obliged to calculate
them from Laplace's and Poisson's formula for the change of
temperature in a gas during adiabatic expansion.

  T/T1 = (p/p1)^{(k - 1/k)}

  Where:

    T, p are the initial temperature and pressure of the gas.

    T1, p1 are the final temperature and pressure of the gas.

    k is the ratio (cp/cv) which, for a monatomic gas, is 1.66.

In the first series of experiments the gas, under a pressure of 128
atmospheres, was cooled down to -210° C.

    p         T            p1           T1
  At.        Deg.          At.       Deg.       Deg.
  125       -210 C.        50       -229.3 C.   43.7 A.
  ...        ...           20       -242.7 C.   30.3 A.
  ...        ...           10       -250.1 C.   22.9 A.
  ...        ...            5       -255.6 C.   17.4 A.
  ...        ...            1       -263.9 C.    9.1 A.

The results of these calculations tend to show that the boiling point
of helium lies below -264° C., at least 20° lower than the value I
have found for the boiling point of hydrogen. If the boiling point of
a gas be taken as a simple function of its density, helium, which,
according to Prof. Ramsay's determination, has a density of 2.133,
more than double that of hydrogen, should liquefy at a much higher
temperature. Both argon and helium have much lower boiling points than
might be expected, judging from their densities. This anomalous
condition may be accounted for by the fact that in each case the
molecular structure is monatomic, as shown by the values obtained for
the ratios of their specific heats.

The permanent character of helium might be taken advantage of in its
application to the gas thermometer. The helium thermometer could be
used to advantage in the determination of the critical temperature and
boiling point of hydrogen. To determine whether the hydrogen
thermometer is of any value at temperatures below -198° C. I carried
out a series of experiments, in which I measured the temperature of
liquid oxygen boiling under reduced pressure. I made use of the
identical thermometer tube employed by T. Estreicher (Phil. Mag. [5]
40, 54, 1898) as a hydrogen thermometer for the same purpose, and
applied the same corrections as were made in his experiments.

                                 Temperature.
  Pressure           Helium Thermometer.   Hydrogen Thermometer.
     Mm.                    Deg.                   Deg.
     741                   -182.6 C.              -182.6 C.
     240                   -191.8 C.              -191.85 C.
      90.4                 -198.7 C.              -198.75 C.
      12                   -209.3 C.              -209.2 C.
       9                   -210.57 C.             -210.6 C.

The results of these experiments prove that the coefficient of
expansion of hydrogen does not change between these limits of
temperature, and that the hydrogen thermometer is a perfectly
trustworthy instrument even when employed to measure the very lowest
temperatures.

I have already pointed out (Wied. Ann., Bd. xxxi, 869, 1887) that the
gas thermometer can be used to measure temperatures which lie even
below the critical point of the gas with which the instrument is
filled. For instance, the critical temperature of hydrogen, which I
have found to be -234.5° C. (Wied. Ann., 56, 133; Phil. Mag. [5] 40,
202, 1898) can be determined by means of a hydrogen thermometer. The
helium thermometer could be used at much lower temperatures, and would
probably give a more exact value for the boiling point of hydrogen
than it is possible to obtain by means of a platinum thermometer.

       *       *       *       *       *




SOME NOTES ON SPIDERS.

By Rev. SAMUEL BARBER.


The instinct of spiders in at once attacking a vital part of their
antagonist--as in the case of a theridion butchering a cockroach by
first binding its legs and then biting the neck--is most remarkable;
but they do not always have it their own way. A certain species of
mason wasp selects a certain spider as food for its larvæ, and,
entombing fifteen or sixteen in a tunnel of mud, fastens them down in
a paralyzed state as food for the prospective grubs.

Perhaps the most entertaining points in connection with spiders are
their concentration of energy, their amazing rapidity of action, and
their inscrutable methods of transition and flotation.

During the past autumn large numbers of these creatures appeared at
intervals. Thus I observed a vast network of lines that seemed to have
descended over the town of Whitstable, in Kent, and which were not
visible the day before or the day after. Many were fifteen to twenty
feet long; they stretched from house to lamppost, from tree to tree,
from bush to bush; and within six or seven feet of the ground I
counted, in a garden, twenty-four or more parallel strands. The
rapidity with which spiders work may be gathered from the fact that,
while moving about in my room, I found their lines strung from the
very books I had, a moment before, been using.

Insect life, as might have been expected after so mild a winter and so
dry a spring and summer, is (1896) intensely exuberant. The balance is
preserved by a corresponding number of Arachnida. On May 25 and 26 the
east wall of the vicarage of Burgh-by-sands was coated with a tissue
of web so delicate that it required a very close scrutiny to detect
it. I could find none of the spinners. Every square inch of the
building appeared coated with filmy lines, crossing in places, but
mostly horizontal, from north to south.

Walking by the edge of a wheatfield in Suffolk on May 14, I observed
all over the path, which was cracked with the drought, dark objects
flitting to and fro. They were spiders--mostly of the hunting order.
Tens of thousands must have occupied a moderate space of the field,
and the cracks in the parched soil afforded them a handy retreat.

In reference to the visitation of spiders at Whitstable during the
autumn and winter of 1895-6, it is right to note that the people of
that place regard them as a sign of an east wind. In this connection
we can note the fact of the phenomenal clouds of flies occurring at
times on the east coast of England; and it would be interesting if
observers could ascertain whether spiders ever cross the Channel and
accompany such visitations of insects.

The production of the flotation line, and its method of attachment,
are the two points to which I ask the attention of observers.

Is it not evident that air (and probably at a high temperature) must
be inclosed within the meshes of the substance forming the line when
it passes from the spinnerets into the atmosphere? The creature with
this substance within its body drops to the ground at once by force of
gravitation; yet, when emitted, the very same substance lifts it into
the air. It has been usual to explain the ascent by the kite
principle, i.e., the mechanical force of the contiguous atmosphere.
But air movements, especially on a small scale, are so capricious and
uncontrollable that, without a directive force, the phenomena seem
quite inexplicable.

Moreover, all my own observations lead me to accept the theory of a
direct propelling force, and I can hardly accept the conclusions on
this point of Mr. Blackwall, though he is an authority on the subject.
The intense rapidity with which the initial movements are made cannot
be reconciled with any theory of simple atmospheric convection; and
illustrations such as the following go to prove that spiders possess
the faculty of weighting or condensing the ends of their threads, and
throwing them, within limited distances, to a point fixed upon.

I was writing, and had two sheets of quarto before me. Perceiving a
small spider on the paper I rose and went to the window to observe it.
To test its power of passing through the air, I held another sheet
about a foot from that on which the creature was running. It ascended
to the edge, and vanished; but in a moment I saw it landing upon the
other sheet through midair in a horizontal direction, and picking up
the thread as it advanced.

In this case there was no air movement to facilitate, nor any time to
throw a line upward, which, indeed, would not have solved the
difficulty. Propulsion appears the only explanation.

The next illustration is more marvelous, and seems to indicate that
some species, at any rate, have the power of movement through the air
in any direction at will.

Some years ago, at a dinner party in Kent, four candles being lighted
on the table, I noticed a thread strung from the tip of one of the
lighted candles close to the flame, and attached to another candle
about a yard off; and all the four lights were connected in this way,
and that by a web drawn quite tight. No little surprise was caused
among the guests on finding that the diamond form of the web was
complete.

No satisfactory explanation of this has been offered, and I can only
suggest that the spinner was suspended at first by a vertical line
from above, and thus swayed itself to and fro, from tip to tip of the
candles. It was certain that the spider could not have ascended from
the table; and it was equally certain that aerial flotation of the
line from a fixed point was impossible, as it involved floating in
four opposite directions. I have seen a creature of this or a nearly
allied species moving laterally through the air of a room in this
way.--Knowledge.

       *       *       *       *       *




ENGINEERING NOTES.


AUSTRIA is turning out a new variety of Mannlicher repeating
rifle for its army, which is the lightest rifle in the world, weighing
3.3 kilogrammes, seven pounds and four ounces, instead of 4.4
kilogrammes, nine pounds eleven ounces, the weight of the old pattern.
All the individual parts in the new rifle, including the locking box,
the magazine and the barrel, are lighter than in the old. The bayonet
and sheath are also made lighter.

A TROLLEY express car system is now in successful operation in
Brooklyn, N.Y. The trolley system of Brooklyn is one of the most
extensive in the world, and many of the outlying districts are now
served with great dispatch. Parcels are collected by wagons, they are
then brought to the cars, and, after being carried to the nearest
express station to their destination, they are then transported again
by wagons. On Sundays the cars are run to carry bicycles.

IN STANISLAU oil gas is being a good deal used for incandescent
lighting, says the Gas World. The gas is used at a pressure of from
1.1 in. to 1.2 in. When 1.7 cubic feet per hour is used the Welsbach
mantle gives 69½ candles at first, 65 candles after 120 hours, 48¼
candles after 500 hours. The fall in lighting power is comparatively
slow with oil gas, and the mantles are not so much worn by lighting
the gas, for the kind of oil gas is not as explosive as that of coal
gas. The mantles are found to last from 400 to 600 hours.

DURING THE construction of the Simplon tunnel every possible
alleviation will be made for the workmen employed, says the Railway
Review. On leaving the tunnel when they are hot and wet through they
will go at once to the douche and bathrooms provided for their
accommodation, where, after a refreshing shower bath, they will resume
their dry clothes. The sheds from which the workmen leave the tunnel
are to be covered in and closed at the sides so as to protect them
from cold. Water will be taken at intervals to the workmen who may
require it, either from the pipe which feeds the drills or from that
which brings water for cooling. No provision has been made as regards
workmen's lodgings, because it is supposed that they will easily find
accommodation in the neighborhood. As it is believed that the
temperature of the rock of the Simplon tunnel may reach a maximum of
104° F., costly measures will have to be taken to cool the air in many
parts where the works are to be carried on.

"RECENT DEVELOPMENTS IN LIGHTHOUSE ENGINEERING" was the title
of a paper read recently at the Institution of Civil Engineers, by Mr.
N.G. Gedye, says the Colliery Guardian. The author pointed out the
marked development which has of late years taken place in the
direction of reducing the length of flash emitted by lighthouse
apparatus to a minimum, and the consequent increase obtained in
intensity. The apparatus now being erected at Cape Leeuwin, Western
Australia, gives a flash of one-fifth of a second duration every five
seconds. It is the most powerful oil light in the world, the flash
being over 145,000 candle power emitted from a pair of dioptric lenses
mounted on a mercury float revolving once every ten seconds. Each of
the two lenses is 8 feet in diameter. The powers of these oil lights
are far exceeded by electric lighthouse lights, there being several in
France up to 23,000,000 candle power, while there has recently been
established at Fire Island, at the entrance to New York Harbor, an
electric light, of French design and construction, of 123,000,000
candle power; this is the most powerful lighthouse light in the world.

DISCUSSING THE use of potassium cyanide for steel-hardening
purposes, T.R. Almond, of Brooklyn, N.Y., suggests that this salt
assists the hardening process because of its powerful deoxidizing
properties, and also because it forms a liquid film on the surface of
the steel, which causes a more perfect contact between the steel and
the water, thereby permitting a more rapid abstraction of heat. The
inevitable formation of a thin coat of oxide is unfavorable to the
process of rapid cooling; and as rapid cooling seems to be the one
thing necessary for success in hardness, any means used for the
removal of a bad conductor of heat, like the black oxide, will be of
advantage, and more especially if this means also results in the
formation of a liquid film on the steel surface having the affinity
for water which, it is well known, is peculiar to potassium cyanide.
Mr. Almond recommends the removal of all scale or oxide from the
surfaces of steel to be hardened, either by pickling or by the
cyanide. Steel covered with a very thin film of oxide will take the
heat less quickly when immersed in hot lead than if the steel be
bright before being immersed. This being the case, it would seem to
follow that, because of a film of oxide, heat will leave steel more
slowly when being cooled by water.

THE GIGANTIC WHEEL, now being erected on the site of the old
bowling green in a corner of the Winter Gardens, Blackpool, was
commenced on December 1, 1895, says the Building News. The work of
erecting the supports was not finished until the third week in March,
and then the most difficult portion of the work, viz., that of
hoisting the axle, was commenced. The axle, a steel forging weighing
over 28 tons and measuring nearly 41 ft. long and 26 in. in diameter,
was forged at the works of Messrs. W. Beardmore & Company, of Glasgow.
The axle and bearings being fixed complete, the work of building the
rims of the wheel will be pushed forward rapidly under the direction
of Mr. Walter B. Basset, who also built the Earl's Court wheel. The
carriages, thirty in number, and each capable of carrying forty
persons, are rapidly approaching completion in the works of Messrs.
Brown, Marshall & Company, of Birmingham. The driving engines and most
of the intermediate gearing are already in position in the engine
house. These engines will operate two steel wire ropes, one on either
side of the rim of the wheel, and arrangements have been made and
provided for in such gearing to enable the wheel to be turned at a
quicker speed than that at Earl's Court. The Blackpool wheel will be
able to carry more passengers per hour than its predecessor in London.
The particulars of the great wheel are: Total height above sea level,
250 ft.; total diameter (across centers of pins), 200 ft.; total
weight, 1,000 tons. The solid axle is of a diameter through the
journals of 2 ft. 2 in., a diameter across the flanges of 5 ft. 3 in.,
length over all 41 ft., and weight 28 tons.

       *       *       *       *       *




ELECTRICAL NOTES.


PORTRAITS of Morse and Fulton are printed on the reverse of the
new two dollar silver certificate, affording a relief to the dreary
monotony of ex-presidents, generals and statesmen.

A MONSTER electric elevator is to be erected at Allegheny, Pa.
It will be large enough to carry up several wagons at once. The new
elevator will save a trip of a mile and a quarter.

AN EXCURSION TROLLEY car on the Milwaukee Street Railway has
700 incandescent lights. The car is 32 feet over all. The platforms
are 5 foot. The floor of the car is carpeted and a few tables for
refreshments are provided.

AMSTERDAM will have next year an international exhibition of
hotel arrangements and accommodations for travelers. Among the
features of the exhibition will be an "electric restaurant," without
waiters, in which visitors will be served automatically with a
complete dinner on pressing an electric button.

PROF. FLEMING has shown by experiments that with a 2,000 volt
alternating current with a water resistance, that the latter is quite
non-inductive, and that the readings of the amperes may be taken, says
the Electrical World, as a measurement of the voltage, and the product
of the volts and amperes will represent correctly the power consumed.

OUR contemporary, The Engineer, suggests doing away with
windsails on board steamers entirely and substituting electric fans.
In warships the fan ought to be placed where room can be found for it
low down in the ship, far below the water line. An electrically driven
horizontal fan, with its motor, can be got into the thickness of a
deck with its beams, if needs be. This would clearly be better than
depending on a flimsy construction, which would certainly be greatly
damaged, if not entirely shot away, in action. If clear decks are
wanted, the windsail is about as inconvenient as it is ugly, and that
is saying a great deal.

SINCE January 1, last, a new and reduced telephone tariff has
been in force in Switzerland, and from reports to hand it appears to
have worked satisfactorily all round. The former charge per annum for
a telephone, with an annual limit of 800 conversations, was 80 francs
(£3 4s.) The new tariff now in force is 40 francs (£1 12s.) per annum,
plus an additional charge of 5 centimes for each local connection. The
charges for interurban connections, with a time limit of three
minutes, are as follows: Up to a distance of thirty-one miles, 3 d.;
up to sixty-two miles, 5 d.; and above sixty-two miles, 7½ d. The
telephone system throughout Switzerland is owned by the government,
and the service, says the Electrician, is first class in every
respect.

"THERE ARE three ways by which high temperature may be
measured," says the Electrical Engineer, London. "The first uses an
air thermometer of refractory material; the second depends on the
change in the resistance of a platinum wire with change in
temperature; and the third is based on the employment of a thermo
couple of relatively infusible metals. According to Messrs. Holborn
and W. Wein, in a paper published in Wiedemann's Annalen, the air
thermometer method was valueless until recently, as suitable vessels
could not be made. But now these are produced from refractory clays,
and permit of measurements up to 1,500° C. (2,732° F.) The results
are, however, vitiated by the effects of capillarity in the interior
of the vessel. The resistance method has also its disadvantages. At
high temperatures the resistance generally increases, but the
temperature coefficient is irregular. The presence of free hydrogen
also affects the resistance. The third or thermopile method is favored
by the authors, who prefer a circuit of platinum and an alloy of
platinum with ten per cent. of rhodium. Temperatures up to 1,600° C.
(2,912° F.) can be measured by it, and it is remarkably constant under
various conditions."

THE LONDON ELECTRICIAN states that at a special meeting of the
South African Philosophical Society held on August 2, a lecture on the
above subject was delivered by Mr. A.P. Trotter, Government
Electrician and Inspector. Toward the end of the lecture the lecturer
rang up the Capetown Telephone Exchange, and asked if any of the
longer post office telegraph lines were clear. The Port Elizabeth line
was then connected up, and by means of a Wheatstone bridge on the
lecture table, the resistance of the line was measured. The lecturer
then observed that, with the extremely sensitive instrument used in
the Government Electrical Laboratory, it was not necessary to use
ordinary electric batteries for signaling to such a distance as to
Port Elizabeth. He disconnected the battery, and, plunging a steel
knife and silver fork into an orange, sent signals by means of the
feeble current thus generated. He then asked the front row of the
audience to join hands, and, putting them in the circuit, sent signals
through their bodies to Port Elizabeth and back by means of the orange
cell. As a concluding experiment an omelette was made "under some
disadvantages," and the cost of the electrical energy was stated to be
only two cents.

"THE QUESTION of injury to the eyes from the electric light is
being prominently discussed by scientists, oculists, and laymen
throughout the country," says the American Journal of Photography.
"While opinion widely differs as to the ultimate injury likely to
result from the rapidly increasing use of electricity, the consensus
of opinion is that light from uncovered or uncolored globes is working
damage to eyesight of humanity. In a discussion of the subject a
London electric light journal in defending its trade feels called upon
to make some important admissions. It says: 'It is not customary to
look at the sun, and not even the most enthusiastic electrician would
suggest that naked arcs and incandescent filaments were objects to be
gazed at without limit. But naked arc lights are not usually placed so
as to come within the line of sight, and when they do so accidentally,
whatever may result, the injury to the eye is quite perceptible. The
filament of a glow lamp, on the other hand, is most likely to meet the
eye, but a frosted bulb is an extremely simple and common way of
entirely getting over that difficulty. The whole trouble can be easily
remedied by the use of properly frosted or colored glass globes. In
any case, however, the actual permanent injury to the eye by the
glowing filament is no greater than that due to an ordinary gas
flame.'"

       *       *       *       *       *





MISCELLANEOUS NOTES.


RUBBER trees are reported found growing in Manatee County, Fla.

JAPAN proposes to build up her commercial navy by giving
subsidies to ship builders on every ton above 1,000, and to ship
owners for ships of 1,000 tons that can make ten knots an hour, the
subsidy being increased for every 500 tons additional burden or every
knot additional speed.

ROSA BONHEUR began to work seriously at painting when she was
about fifteen, and donned male attire so that she could go about
without attracting attention. She wore it so naturally that no one
ever suspected her of being a girl, and found it so comfortable that
she has worn it ever since to work in. She and Mme. Dieulafoy, the
wife of the explorer, are the only two women in France who are legally
authorized to appear in public in men's clothes.

A DEVICE for permitting the unsophisticated guest to blow out
the gas in his bedroom at the city hotel without inconvenience to
himself or anybody else has been devised. The gas burner is made of a
metal having great expansive and contractive properties. The gas is
turned on in the regular way and a small screw is turned which admits
a small flow of gas through the burner. The gas is lighted, and the
heat expands the metal and automatically opens a valve permitting a
full flow of gas. The gas can be turned off in the ordinary way, but
if the gas is blown out the metal contracts, closing the valve, and
all the gas that escapes is the very small quantity admitted by the
screw valve.

A MOVEMENT is on foot in Europe having for its object the
securing of a complete census of the inhabitants of all the civilized
countries of the world. With this end in view the several governments
are to be approached with the request that they will endeavor to
decide upon a mutual date for counting the people under their various
jurisdictions. Heretofore the different countries have taken their
census on different dates, and it has been impossible to obtain
accurate statistics in regard to the world's population at any one
particular period. It is suggested that the last year of the present
century or the first year of the coming century would be the most
appropriate date for obtaining statistics.

OF THE 376 suicides who ended their lives in New York last
year, by far the greater number were divorced people, says the Medical
Review. From a table prepared for the year 1895, it is shown that
there were in Germany during that year 2,834 suicides of men either
divorced or separated from their wives and 948 suicides of widowers,
as against only 286 suicides of married men. It is also shown that 343
women separated from their husbands and 124 widows died by their own
hands, in contrast with 61 married women and 87 unmarried. In
Wurtemburg, to every million inhabitants, there are 1,540 lunatics
among divorcés or women separated from their husbands and 338 among
the widows, while there are only 224 among unmarried women. There are
1,484 lunatics among the men who are divorced or separated from their
wives, 338 among the widowers, and only 236 among the bachelors.

THE QUARTERLY list of American tin plate works, which was
published in the Metal Worker a short time ago, shows that on July 1
there were thirty-six complete tin plate plants rolling their own
black plates in actual operation in the United States and three in
course of construction. The active plants possessed an aggregate of
179 tin mills, having an estimated yearly capacity of about 5,500,000
boxes of tin plates. In addition to these establishments there were
thirty-one tin plate dipping works, without rolling mills, possessing
an aggregate of 169 tinning sets. At the end of June the production of
American tin plate is estimated to have been going on at the rate of
over 4,000,000 boxes yearly. During the last quarter the New Castle
Steel and Tin Plate Company, of New Castle, Pa., has completed large
extensions to its works, making it an eighteen-mill plant. This gives
the United States the largest and most complete tin plate works in the
world. Its annual capacity is three-quarters of a million boxes.

THE MONITEUR VINICOLE has recently published a statement
showing the wine production of the various countries of the world.
From this statement it appears the yield in France amounted in the
years 1895 and 1894 to 587,127,000 gallons and 859,162,000 gallons
respectively; in Algeria to 83,549,000 and 80,124,000 gallons; Tunis,
3,956,000 and 3,936,000: Italy, 469,555,000 and 539,000,000; Spain
379,500,000 and 528,000,000; Portugal, 43,890,000 and 33,000,000;
Azores, Canaries, and Madeira, 4,620,000 and 2,640,000; Austria,
66,000,000 and 88,000,000; Hungary, 63,030,000 and 46,103,000; and
Germany, 80,190,000 and 110,000,000 gallons. In Turkey and Cyprus the
production last year amounted to 52,800,000 gallons, and this compares
with an average yield of 40,000,000 gallons. In Bulgaria the yield was
26,400,000 gallons; Servia, 17,600,000; Greece, 35,200,000; Roumania,
68,640,000; Switzerland, 27,500,000; the United States, 89,700,000;
Mexico, 1,980,000; Argentine Republic, 29,700,000; Chile, 33,000,000,
Brazil, 7,700,000; Cape of Good Hope, 2,420,000; Persia, 594,000; and
Australia, 3,300,000 gallons.

THE Historical Museum of Hesse Cassel, in Germany, says the
Carpenter and Builder, contains a most remarkable collection of
curiosities. It is in the form of a wooden library, composed of five
hundred and forty volumes of folio and quarto sizes. The books are
made of the different specimens of trees found in the famous park of
Wilhelmshoehe. On the back of each of these singular books is pasted a
large shield of red morocco, which bears the popular and scientific
names of the tree and the family to which it belongs. Each label is
inlaid with some of the bark of the tree, the moss and lichen, and a
drop or two of the resin, if the tree produces it. The upper edge of
the book shows the tree in its youth, cut from a horizontal section,
with the sap in the center and the eccentric circles. The same method
prevails with the lower edge, showing the changes that have taken
place. The interior of the book, in the shape of a box, contains in
manuscript the history of the tree, with numerous hints as to its
treatment, capsules filled with seeds, buds, roots, leaves, and so on.
The inner sides show the diverse transformations which take place from
bloom to fruit.

       *       *       *       *       *




SELECTED FORMULÆ.


AMBROSIA SIRUP.--

Raspberry sirup..................... 8 vol.
Vanilla sirup....................... 8 "
Hock wine........................... 1 "


AMYCOSE.--

Shaved ice.......................... ½ tumblerful.
Raspberry juice..................... 1 fl. oz.
Orange sirup........................ 2   "
Juice of half an orange.

Shake well, add soda water, and before serving add a small, thin slice
of orange or pineapple. Serve with two straws in a 14 oz. tumbler.


BANANA SIRUP.--

Cut the fruit in slices and place them in a jar; sprinkle with sugar
and cover the jar, which is then enveloped in straw and placed in cold
water, and the latter is heated to the boiling point. The jar is then
removed, allowed to cool, and the juice is poured into bottles.


BANANA CREAM.--

Shaved ice.......................... ½ tumblerful.
Banana sirup........................ 2 fl. oz.
Cream of milk....................... 8 "

Shake well, add a few pieces of banana, and fill with soda water,
using the fine stream, and serve in a 12 oz. tumbler with a spoon and
straws.


CHARLOTTE RUSSE.--

Shaved ice.......................... ½ tumblerful.
Vanilla sirup....................... 1 fl. oz.
Cream............................... 6   "
One egg.

Shake and fill with soda water, using the fine stream. Serve in a 14
oz. tumbler with a spoon; it will have a head like a charlotte russe.


CHOCOLATE SIRUP.--

Best chocolate...................... ½ lb.
Gelatin............................. 3 oz.
Water............................... 4 pts.
Sugar............................... 7 lb.

The chocolate and gelatin are dissolved in the water by boiling, and
then the sugar is added and stirred until dissolved; or,

Chocolate........................... ½ lb.
Glycerin............................ 12 fl. oz.

Heat together on hot water bath until the chocolate is melted,
constantly stirring, and then add enough sirup to make 1 gallon. The
sirup must be added in small portions at first, under constant
stirring, and the result will be a superior sirup. Extract of vanilla
may be added if it is desired to further improve the taste.


CLAM JUICE SHAKE.--

Clam juice.......................... 1½ fl. oz.
Milk................................ 2  "
Soda water.......................... 5  "

Add a pinch of salt and a little white pepper to each glass; shake
well.


COFFEE SIRUP.--

Mocha coffee........................ ½ lb.
Java coffee......................... ½  "
Boiling water....................... 1 gal.
Granulated sugar.................... 10 lb.

Boil together, or pass through a suitable filter coffee pot, until one
gallon of infusion is obtained; let it settle and add the sugar.


EGG LEMONADE.--

Shaved ice.......................... ½ tumblerful.
One egg.
Juice of one large lemon.
Powdered sugar...................... 3 teaspoonfuls.
Water............................... 6 fl. oz.

Shake thoroughly. Draw a small quantity of soda water, fine stream
only, and grate a little nutmeg on top.


EGG PHOSPHATE.--

Draw into a thin 9 oz. tumbler, 2 oz. of Maltese (red) orange sirup,
and add an egg, a few squirts of acid phosphate, and a small piece of
ice; shake well, fill shaker with soda water--using the large stream
only--and strain.


ORANGE PHOSPHATE.--

  RED ORANGE PHOSPHATE.

Red orange sirup.................... 6 pints.
Orange wine......................... 1  "
Pineapple sirup..................... 1  "
Acid solution phosphates............ 8 fl. oz.

  TANGERINE PHOSPHATE.

Tangerine sirup..................... 7 pints.
Pineapple sirup..................... ½  "
Muscatel............................ ½  "
Acid solution of phosphates......... 8 fl. oz.

--Montreal Pharmaceutical Journal.


AMERICAN METAL POLISHING PASTE.--

Bohemian Tripoli powder............. 1 pound.
Spanish whiting..................... 1  "
Commercial red oxide of iron........ ½  "
Common petrolin-burning oil......... 1 ounce.
Glycerine...........................   q. s.
Water...............................   q. s.
Oil of citronella................... ½ ounce.

Thoroughly mix the powders, then add the petrolin, etc.--Mag.
Pharmacy.


CEMENT FOR PORCELAIN LETTERS.--

Solution sodium silicate............ 30 parts.
Slaked lime......................... 45 "

Mix, and add:

Litharge............................ 30 parts.
Glycerine.............. quantities sufficient.

Make a paste, and use immediately.

       *       *       *       *       *




THE GREAT KRUPP WORKS.


More than 1,250,000 tons of coal are consumed yearly by the famous
Krupp works at Essen, Westphalia, commenced in 1810 by Peter Friedrich
Krupp, and now in the possession of Herr Friedrich Krupp, member of
the Reichstag. The establishment consists, according to the Eisen
Zeitung, of two steel works, with 15 Bessemer converters; four
steelworks, with Siemens-Martin open hearth furnaces; iron, steel and
brass foundries; puddling, melting, reheating and annealing furnaces;
draw benches; a hardening and tempering department; file manufactory;
rolling mills for plates, rails and tires; railway spring and wheel
manufactory; steam hammers, forges, axle turning shop, boiler shop,
engineering and repair shop. Besides the above and many other
departments, at Essen, connected with the making of cannons, there are
steel works at Annen, in Westphalia, three collieries in Westphalia,
besides participation in several others; 547 iron mines in Germany;
various iron mines at Bilboa, in Spain; four iron works, including one
at Duisburg, one at Engers, one at Neuwid, and one at Sahn; various
quarries of clay, sandstone, etc.; four steamers, and artillery ground
at Meppen, Hanover. The property owned extends over 974 hectares, and
the number of hands employed in the mines and steelworks is 25,301.
There are altogether 1,500 furnaces of various kinds, 3,000 engines
and machine tools, 22 roll trains, 111 steam hammers, 2 hydraulic
presses, 263 stationary boilers, 421 steam engines, representing
together a force of 33,139 horse power, and 430 cranes, including
travelers, having a collective lifting power of 4,662 tons. The total
length of the shafting is 8.8 kiloms. (5½ miles), and that of
railways, standard and small gage, 85 kiloms. (53 miles), worked by 32
regular trains, with 33 locomotives. The annual consumption of coal
amounts to 1,253,161 tons, and that of lighting gas to 12,000,000
cubic meters, while there are 573 arc and 1,804 incandescent electric
lamps.

       *       *       *       *       *




PHYSICS WITHOUT APPARATUS.


The Chain and the String.--To the extremity of a string about 18 in.
in length attach a chain about 15 in. in length, the extremities of
which are united. Holding the string vertically between the fingers,
give it a rapid rotary motion. The chain will first open out as seen
at A of the figure. Upon increasing the velocity of rotation, it will
be thrown out farther and farther until it finally forms a circle in a
horizontal plane. In this motion, the string forms a sort of conoidal
surface, distended by centrifugal force.

[Illustration: The Chain and the String]

B of the figure gives the exact aspect that the arrangement offers to
the eye during the revolution. In the same way, a penholder attached
by one of its extremities to a string assumes an almost horizontal
position.

This experiment illustrates the principle of centrifugal force.

A Coin Rolling Upon a Parasol.--In treatises upon physics and
mechanics inertia is defined as follows: No particle of matter in a
state of rest possesses within itself the power of putting itself in
motion; or, if it be moving, of bringing itself to a state of rest.

As an example of this principle, we may recall here the trick
performed by certain jugglers, and that consists in making a coin roll
over the top of a Japanese paper parasol. The parasol is revolved very
rapidly, and, to the eyes of the spectator, the coin seems to remain
immovable. It is, in reality, the parasol that revolves under the
coin.

Breaking Stones with the Fist.--It is through the live force acquired,
or inertia at rest, that stones are broken by a blow of the fist. This
experiment is performed as follow: The right hand being properly
bandaged with a handkerchief, the stone to be broken is taken with the
left and allowed to rest upon a larger stone or upon an anvil. Then
the stone to be broken is struck with the right fist, while care is
taken to raise it a slight distance above the anvil just before the
fist touches it. The stone then takes on the velocity of the fist that
strikes it, and coming into violent contact with its support, is very
promptly broken.

As simple as this experiment is, it always surprises the spectators.

Experiment on Inertia.--It is not impossible to remove from a table
set for a guest a large napkin employed in lieu of a table cloth,
without disarranging the objects placed upon it. To this effect, it
suffices to give the napkin a quick horizontal jerk in stiffening the
edges held by the hands.

We recommend our readers to try this experiment only with table ware
of slight value, for one cannot always be sure of succeeding
immediately. Tinware may be employed very advantageously.

The Dice and the Dice Box.--A dice box and two dice are held in the
hand, and the question is to throw one die into the air and catch it
in the box. This is not difficult, but the difficulty is to cause the
second to enter, for if this be thrown into the air, the first, which
is already in the box, will fly into the air likewise and fall
outside. In order to make the second enter while the first is already
in the box, it must not be thrown into the air, but the hand and the
box must be quickly lowered in freeing it, so that the first die,
which is in the box, shall be at a less height than the second, which
is in the fingers. The dice fall less quickly than the hand and the
box.

       *       *       *       *       *




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