The Project Gutenberg eBook of American Horological Journal, Vol. I, No. 1, July 1869: Devoted to Pratical Horology
    
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Title: American Horological Journal, Vol. I, No. 1, July 1869: Devoted to Pratical Horology

Editor: George B. Miller

Release date: April 17, 2022 [eBook #67859]

Language: English

Original publication: United States: G. B. Miller, 1873

Credits: The Online Distributed Proofreading Team at https://www.pgdp.net (This file was produced from images generously made available by The Internet Archive)


*** START OF THE PROJECT GUTENBERG EBOOK AMERICAN HOROLOGICAL JOURNAL, VOL. I, NO. 1, JULY 1869: DEVOTED TO PRATICAL HOROLOGY ***





  AMERICAN

  Horological Journal.

  VOL. I.      NEW YORK, JULY, 1869.      NO. 1.




  CONTENTS.


  ASTRONOMY IN ITS RELATIONS TO HOROLOGY,            5

  WATCH AND CHRONOMETER JEWELLING,                  11

  HINTS ON CLOCKS AND CLOCK MAKING,                 15

  NOTICES OF NEW TOOLS,                             17

  GREENWICH OBSERVATORY,                            17

  PINIONS,                                          20

  NEW THREE-PIN ESCAPEMENT,                         23

  ENGLISH OPINION OF AMERICAN WATCH MANUFACTURE,    23

  CORRESPONDENCE,                                   24

  ECLIPSE OF THE SUN,                               25

  DIAMOND CUTTING,                                  25

  ALLOYS OF ALUMINUM WITH COPPER,                   25

  EQUATION OF TIME TABLE,                           28

⁂ _Address all communications for_ HOROLOGICAL JOURNAL _to_ G. B.
MILLER, _P. O. Box 6715, New York City. Publication Office 229
Broadway._




Astronomy in its Relations to Horology.

NUMBER ONE.


However accurate an instrument for the mensuration of time may be,
it would be of little use for close observation unless we have some
standard by which to test its performance. We look to Astronomy to
furnish us with this desideratum, nor do we look in vain. The mean
sidereal day, measured by the time elapsed between any two consecutive
transits of any star at the same meridian, and the mean sidereal
year--which is the time included between two consecutive returns of the
sun to the same star--are immutable units with which all great periods
of time are compared; the oscillations of an isochronous pendulum
affording us a means of correctly dividing the intermediate space into
hours and days.

We must premise that the whole theory of taking time by sidereal
observations is based on angular motion, the mensuration of one of
the angles of motion giving a measurement of space, so that to say
space, or distance, is equivalent to saying time. From noon of one
day to noon of another is the whole problem to be solved by correct
division. The astronomical day begins at noon, but in civil law the
day is dated from midnight. So in the year the astronomical day is
dated December 31, while in common reckoning the 1st of January is the
initial point. This day is divided into twenty-four hours, counted in
England, America, and the most of the Continental nations of Europe, by
twelve and twelve. The French astronomers, however, adopted the decimal
system, for ease in the computation. Thus they divided the day into
ten hours, the hour into one hundred minutes, and the minute into one
hundred seconds. This plan was in conformity with the French system
of decimal weights and measures. Again, in Italy, the day was divided
into twenty-four hours, but counting from one to twenty-four o’clock.
The French system presents some features well worthy of adoption, as it
gives results so much more easy in computation--a facility unattainable
in the common division; yet it did not come into general use in other
countries, and although some French astronomers still hold to the
system, it is gradually dying out.

At one time during the Revolution in France a clock in the gardens of
the Tuileries was regulated to show time by the decimal system.

For the Horologist the mean length of the day is sufficient to show the
rate of his instrument for that particular day, but the astronomical
and civil division requires a much longer period of observation. This
is obtained by the position of the mean annual equinoxes or solstices,
and is estimated from the winter solstice, the middle of the long
annual night under the North Pole; and the period between this solstice
and its return is a natural cycle, peculiarly suited for a standard of
measurement.

Even with such a standard as the civil year of 365d. 5h. 48m. 49.7s.,
the incommensurability that exists between the length of the day and
the real place of the sun makes it very difficult to adjust the ratio
of both in whole numbers. Were we to return to the point in the earth’s
orbit in exactly 365 days, we would have precisely the same number
of days in each year, and the sun would be at the same point on the
ecliptic at the same second at the beginning and end of the year. There
is, however, a fraction of a day, so that a solar year and civil are
not of equal duration.

It is thus we have our bissextile year, from the fact that the
inequality amounts to nearly a quarter of a day, so that in four years
we have a whole day’s gain; but not exactly, because a fraction still
remains to be accounted for. Now, if we should suppress the one day
of leap-year once at the end of each three out of four centuries, the
civil would be within a very small fraction equal to the solar year,
as given by observation; this small fraction would be almost entirely
eliminated, provided we suppressed the bissextile at the end of every
four thousand years. Were this fraction neglected, the beginning of the
new civil year would precede the tropical by just that much, so that in
the course of 1507 years the whole day’s difference would obtain.

The Egyptian year was dated from the heliacal rising of the star
Sirius; it contained only 365 days. By easy computation it can be
shown that in every 1461 years a whole year was lost; this cycle was
called the Sothaic period, in which the heliacal rising of Sirius
passed through the whole year and took place again on the same day.
The commencement of that cycle took place 1322 years before Christ.
The year by the Roman calendar was dated by Julius Cæsar the 1st of
January, that being the day of the new moon immediately following the
winter solstice in the 707th year of Rome. Christ’s nativity is dated
on the 25th of December, in Cæsar’s 45th year, and the 46th year of the
Julian calendar is assumed to be the 1st year of our era. The preceding
year is designated by chronologists the 1st year before Christ, the
dates thence running backward the same as they run forward subsequent
to that period.

Astronomically, that year is registered 0; the astronomical year begins
at noon on the 31st of December, and the date of any observation
expresses the number of days and hours which have actually elapsed
since that time, the 31st of December--Year 0.

The year is divided into months by old and almost universal consent,
but the period of seven days is by far the most permanent division
of a rotation of the earth around the sun. It was the division long
before the historic period. The Brahmins in India used it with the same
denominations as at the present day the Jews, Arabs, Egyptians, and
Assyrians. “It has survived the fall of empires, and has existed among
all successive generations, a proof of their common origin.”

Nothing can be more interesting in the study of astronomy than its
chronological value. La Place says: “Whole nations have been swept
from the earth, with their languages, arts, and sciences, leaving but
confused masses of ruins to mark the place where mighty cities stood;
their history, with but the exception of a few doubtful traditions, has
perished; but the perfection of their astronomical observations marks
their high antiquity, fixes the periods of their existence, and proves
that even at that early time they must have made considerable progress
in science.”

The earth revolving around the sun in an ellipse, the position of the
major axis of the orbit would indicate something in regard to eras in
astronomy extending not only beyond the historical period, but so far
back in the past that imagination is almost at fault. The position of
the major axis of the orbit depends on the direct motion of the perigee
and the precession of the equinoxes conjointly, the annual motions
respectively being 11´´.8 and 50´´.1, the two combined motions being
61´´.9 annually. A tropical revolution is made in 209.84 years. This
being a constant quantity, we may ascertain when the line of the major
axis coincided with the line of the equinoxes. This occurrence took
place about 4,000 or 4,090 years before the year 0. In the year 6,483
the major axis will again coincide with the line of the equinoxes,
but then the solar perigee will coincide with the vernal equinox. So,
it will be seen that the period of revolution is 20,966 years. But in
the progress of this revolution there must have been a time when the
major axis was perpendicular to the line of the equinoxes. A simple
calculation will show that the eventful year was 1250; and so important
is this event considered, that La Place, the immortal author of the
_Méchanique Céleste_, proposed to make the vernal equinox of this year
the initial day of the year 1 of our era. Again, at the solstices the
sun is at the greatest distance from the equator; consequently the
declination of the sun is equal to the obliquity of the ecliptic.
The length of a shadow cast at noonday from the stile of an ordinary
sun-dial would accurately determine the precise time on which this
position occurs.

Though wanting in accuracy, such a measurement is of interest, from the
fact that there are recorded observations of this kind that were taken
in the city of Layang, in China, 1100 years before our present era is
dated. This observation gives the zenith distance of the sun at the
moment of the observation. Half the sum of the zenith distances gives
the latitude, and half their difference gives the obliquity of the
ecliptic at the period. Now the law of the variation of the ecliptic
is well known, and modern computation has verified both the moment
of taking the observation and the latitude of the place. Eclipses
were the foundation of the whole of Chinese chronology, and recorded
observations prove the civilization of that strange race for 4700 years.

Horology, with astronomy, was not neglected even as early as 3102 years
before Christ, as the following will show.

The cycles of Jupiter and Saturn are very unequal, the latter being a
period of 918 years; the mean motion of the two planets was determined
by the Indians in that part of the respective orbits where Saturn’s
motion was the slowest and Jupiter’s the most rapid. This observed
event must have been 3102 years before, and 1491 after the year 0; but
the record shows that the observation was taken before the last-named
date.

Since both solar and sidereal time is estimated from the passage of
the sun and the equinoctial point across the meridian of the place of
observation, the time will vary in different places by as much as the
passage precedes each. It being obvious that when the sun is in the
meridian at any one place, it is midnight at a point on the earth’s
surface diametrically opposite; so an observation taken at different
places at the same moment of absolute time, will be recorded as having
happened at different times. Therefore when a comparison of these
different observations is to be made, it becomes necessary to reduce
them by computation to what the result would have been had they been
taken under the same meridian at the same moment of absolute time. Sir
John Herschel proposed to employ mean equinoctial time, which is the
same for all the world. It is the time elapsed from the moment the
mean sun enters the mean vernal equinox, and is reckoned in mean solar
days and parts of days. This difference in time is really the angular
motion of the earth, and by measuring it the longitude of any place on
the surface of the earth can be determined, provided we have a standard
point of departure, and an instrument capable of accurately dividing
the time into small quantities during its transit from the meridian on
which it was rated.

As will be hereafter shown, the axis of the earth’s rotation is
invariable. Were the position of the major axis of the earth’s orbit
as immutable, an observation of any star on the meridian taken at
any place would always be the same. Again, the form of the earth has
an important effect; the equatorial diameter exceeds the polar, thus
giving a large excess of matter at the equator. Now the attraction of
an external body not only draws another to it in its whole mass, but,
as the force of attraction is inversely as the square of the distance,
it follows that the attracted body would be revolved on its own centre
of gravity until its major diameter was in a straight line with the
attracting body.

The sun and moon are both attracting bodies for the earth; the plane
of the equator is at an angle to the plane of the ecliptic of 23° 27´
34´´.69, and the plane of the moon’s orbit is inclined to it 5° 8´
47´´.9 Now from the oblate form of the earth, the sun and moon, acting
obliquely and unequally, urge the plane of the equator from its own
position from east to west, thus changing the equinoctial points to the
extent of 50´´.41 annually.

This action, were it not compensated by another force, would in time
alter the angle of the ecliptic until the equatorial plane and the
ecliptic coincided. There are few but have seen the philosophical toy
called the Gyrascope. This toy, on a miniature scale, gives a fine
illustration of the force brought in to correct the combined action of
the sun and moon on the obliquity of the equator. The rotation of the
earth is held in its own plane by its own revolution, the same as the
gyrascope seems to overcome the laws of gravitation by its force of
revolution.

But not only do the sun and moon disturb the plane of the ecliptic,
but the action of other planets on the earth and sun is to be taken
into account. A very slow variation in the position of the plane of the
ecliptic, in relation to the plane of the equator, is observed from
these influences. It must be remembered that a very slight deviation
in the angle can and would be detected by observation with modern
instruments. We do find that this attraction affects the inclination of
the ecliptic to the equator of 0´´.31 annually.

This motion is entirely independent of the form of the earth. Now,
if we assume that the sun and moon give the equinoctial points a
retrograde motion on the ecliptic, we must deduct the influence of the
planets. We may then calculate the mean disturbance by subtracting
the latter from the former--the difference is settled by both theory
and observation to be 50´´.1 annually. This motion of the equinoxes
is called the precession of the equinoxes. Its consideration forms a
very important element in the estimation of time, as the position of
the various fixed stars, though so very distant, are all affected in
longitude by this quantity of 50´´.1--being an increase of longitude.
Therefore, if we were to calculate the position of any given star in
order to get a transit for mean time, or true time, we must take this
quantity into consideration. The increase is so great that the earliest
astronomers, even with their imperfect modes of observation, detected
it. Hipparchus, 128 years before Christ, compared his own observations
with those of Timocharis, 153 years before. He found the solution of
the problem the same as Diophantus found the solution of the squares
and cubes, by analysis. In the time of Hipparchus, the sun was at a
point 30° in advance of its present position, for it then entered into
the constellation of Aries near the vernal equinox.

At the present time the position of the equinoctial points shows a
recession of the whole, 30° 1´ 40´´.2. At this rate of motion the
constellations called the Signs of the Zodiac are some distance from
the divisions of the ecliptic that bear their names. At the rate
of 50´´.1 the whole revolution of the equinoctial points will be
accomplished in 25,868 years; but this is again modified because the
precession must vary in different centuries for the following reasons:
the sun’s motion is direct, the precession retrograde; therefore, the
sun arrives at the equator sooner than he does at the same star of
observation. Now, the tropical year is 365d. 5h. 48´ 49´´.7; and as the
precession is exactly 50´´.1, we must suppose it takes some time for
the sun to move through that arc. By direct observation it is found
that the time required for such translation is 20´ 19´´.6. By adding
this amount to the tropical year we have the sidereal year of 365d.
6h. 9´ 9´´.6 in mean solar days. This amount of precession has been
on the increase since the days of its first recorder, Hipparchus, as
the augmentation amounts to no less than 0.´´455. By adding that to the
known precession we find that the civil year is shorter now by 4´´.21
than in his time; but, as a great division of time, the year can be
changed by this cause not more than 43.´´

The action of the moon on the accumulation of matter at the earth’s
equator is a source of disturbance that in very accurate observations
for time should be eliminated. Thus the moon, with the conjoint action
of the sun, depending on relative position, causes the pole of the
equator to describe a small ellipse in the heavens with axes of 18´´.5
for the major, and 13´´.674 for the minor; the longer axis being
directed to the pole of the ecliptic. This inequality has a period
of 19 years,--it being equal to the revolution of the nodes of the
lunar orbit. The combination of these disturbances changes, by a small
quantity, the position of the polar axis of the earth in regard to the
stars, but not in regard to its own surface. With so many disturbing
causes, we must add that of Jupiter, whose attraction is diminishing
the obliquity of the ecliptic by 0´´.457 according to M. Bessel.

The results of all these forces must affect the position of all the
stars and planets as seen from our earth. Their longitudes being
reckoned from the equinoxes, the precession of these points would
increase the longitude; but as it affects all the stars and planets
alike, it would make no real or apparent change in their relative
positions. Nutation, however, affects the celestial latitudes and
longitudes, as the real motion of the earth’s polar axis changes the
relative positions. So great is the change that our present pole star
has changed from 12° to 1° 24; in regard to the celestial pole, the
gradual approximation will continue until it is with 0° 30´, after
which it will leave the pole indefinitely until in 12,934 years α Lyræ
will be the pole star.

So far we have given only the causes that affect the meridian, and
consequently our standard for time; but that point being established
for the yearly and diurnal revolutions, it becomes necessary to find
some means to divide the day into minute fractional parts, such as
seconds and parts of seconds. This, it has been stated, is effected
by means of an isochronous pendulum. On this instrument no comment is
required but of the causes that disturb its accuracy much is needed.
In 1672, at Cayenne, the astronomer Richter, while taking transits
of fixed stars, found his clock lost 2´ 28´´ per day. This was an
error that arrested his attention, and he immediately attributed it
to some variation in the length of the pendulum--due to other causes
than atmospheric changes and expansion. He determined the length of a
pendulum beating seconds in that latitude, which was 5° N. in South
America. He found that that pendulum was shorter than one beating
seconds in Paris, by 0833+ of an inch. Now, if the earth was a sphere,
the attraction of gravitation at all places on its surface would be
equal, and the oscillations of a pendulum would also be equal, + or
- the disturbing effect of centrifugal force--an amount that can be
easily determined. The real reason of the variation is found in the
configuration of the earth.

The amount of the attraction of gravitation at any point of the earth’s
surface is found by the distance traversed by any body during the
first second of its fall. The pendulum is a falling body, and may be by
the same analysis reasoned on that pertains to the laws of gravitation;
the centrifugal force is measured by any deflection from a tangent to
the earth’s surface in a second.

It follows that the centrifugal force at the poles, where there is
the least motion, would not be equal to the force of gravitation, and
at the equator must be exactly equal; but the deflection of a circle
from a tangent measures the intensity of the earth’s attraction, and
is equal to the versed sine of the arc described during that time,
the velocity of the earth’s rotation being known, the value of the
arc is deducible. The centrifugal force at the equator is equal to
¹⁄₂₈₉th part of the attraction of gravitation. Again, the uniformity
of the earth’s mass becomes an object of consideration. Assuming that
the figure of the earth is an ellipsoid of rotation, we will show the
relation that form bears to the equal oscillation of a pendulum.

Taking the earth as a homogeneous mass, analysis gives us the certainty
that if the intensity of gravitation at the equator be taken as unity,
the increase of gravity to the poles eliminating the differences of
the centrifugal force must be = to 2.5, the ratio of the centrifugal
force to that of gravitation at the equator. Now, taking the 2.5 of
.346 = 1/115.2, this then must be the total increase of gravitation.
Did we know the exact amount of increase at every point, from the
equator to the poles, a perfect map of the form of the earth could
be produced from calculation; experiment being from physical causes
totally impracticable. The following analysis, quoted from an eminent
physicist, gives a very lucid idea of the reasoning:

“If the earth were a homogeneous sphere without rotation, its
attraction on bodies on its surface would be everywhere equal. If it
be elliptical and of variable density, the force of gravity ought to
increase in intensity from the equator to the pole as _unity plus_
a constant quantity multiplied into the square of the sine of the
latitude. But for a spheroid in rotation the centrifugal varies by
the law of mechanics, as the square of the sine of the latitude from
the equator, where it is greatest, to the poles, where it is least.
And as it tends to make bodies fly off the surface, it diminishes the
force of gravity by a small quantity. Hence, by gravitation, which
is the difference of these two forces, the fall of bodies ought to
be accelerated from the equator to the poles proportionably to the
square of the sine of the latitude, and the weight of the body ought to
increase in that ratio.”

Assuming the above reasoning to be correct, it follows, that the rate
of descent of falling bodies will be accelerated in the transition
from the equator to the poles. Now, it has been before stated that
the pendulum is a falling body; therefore, with the same length of
pendulum, the oscillations at the pole should be faster than at the
equator. Theory, in this case, is verified; for it has been proved by
experiments, repeated again and again, that a pendulum oscillating
86,400 times in a mean day at the equator, will give the same number of
oscillations at any other point, provided its length is made longer in
the exact ratio as the square of the sine of the latitude.

The sequence to be derived from all the foregoing considerations is,
that the whole decrease of gravitation from the equator to the poles
is 0.005.1449, which subtracted from the 1/155.2 gives the amount
of compression of the earth to be nearly 1/285.26. But this form
of the earth would give the excess of the equatorial axis over the
polar about 26¹⁄₂ miles. The measurement is confirmed by Mr. Ivory
in his investigations on the five principal measurements of arcs of
the meridian in Peru, India, France, England, and Lapland. He found
that the law required an ellipsoid of revolution whose equatorial
radius should be 3,962.824 miles, and the polar 3,949.585 miles; the
difference is 13.239 miles; this quantity multiplied by two gives
26.478 as the excess of one diameter over the other. Thus, by two
different processes the figure of the earth has been determined; but
another remains that is the result of pure analysis, derived from the
nutation and precession of the equinoxes--for, as explained before,
these effects are caused by the excess of matter at the earth’s
equator. The calculation does not lead us to certainty, but it does
show the compression to be comprised between the two fractions ¹⁄₂₇₀
and ¹⁄₅₇₃. There is this advantage in the lunar theory, that it takes
the earth as a whole, disregarding any irregularities of surface, or
the local attractions that influence the pendulum--the difficulties of
measuring an arc of the meridian being an obstacle to perfect accuracy.

The form of the earth has, however, a value confined not alone to those
interested in horology--it furnishes us with a standard of weights and
measures. In England and the United States, the pendulum is the unit of
mensuration, or at least the common standard from which measurement is
derived. It has been shown that, deducting the effects of nutation, the
axis of the earth’s rotation is always in the same plane. Now, the mass
being the same constant quantity, a pendulum oscillating seconds at the
Greenwich Observatory, has been adopted by the English Government as
its standard of length. Oscillating in vacuo at the level of the sea,
at 62° Fahr., Captain Kater found its approximate length to be 39.1393
inches; as this must be invariable under the same circumstances, it
becomes a standard for all time. The French deduced their standard from
the measurement of the ten-millionth part of a quadrant of the meridian
passing through Formentera and Greenwich. They have also adopted the
decimal system; yet it seems to prove that nothing under the sun is
new, for over forty centuries ago the Chinese used the decimal system
in the division of degrees, weights, and measures.

The antiquity of the pendulum is also shown by the fact that the
Arabs were in the habit of dividing the time in observations, by its
oscillations, when Ibn Junis, in the year one thousand, was making
his astronomical researches. Before we lose sight of the influence
of the form of the earth on the pendulum, it may be well to state
another source of disturbance, arising from the combined influence of
the earth’s rotation and the fact that a body moving in its own plane
seeks to maintain that plane. It will be seen from the very beautiful
experiment showing the rotation of the earth, that if a body like a
pendulum be suspended so as to be free in every direction, and not be
influenced by the motion of the earth when set in oscillation in any
plane, that that plane will preserve its line of motion, while the
earth in its motion beneath the body can be seen to slowly move, as
though the minute hand of a watch were made stationary while the dial
revolved. The same principle is the one that maintains the spinning-top
in a parallel position to the horizon, or the gyrascope in its
apparently anomalous defiance of all the laws of gravitation. In the
pendulum this tendency to preserve the same plane of motion becomes a
cause of error--slight, it is true, but can be very easily remedied by
so placing it that the plane of oscillation shall be parallel to the
equator. It will be readily seen that this precaution will become more
important as we recede from the equator; for if we were to suspend a
pendulum at the pole in a true line with the axis of rotation, and if
the plane of vibration remained constant, the earth would turn once
around that plane in the diurnal period. During this time there would
be a continuous torsion on the point of suspension, that would in time
materially affect the accuracy of the instrument. The reasoning holds
good for every latitude--degree of influence being the only difference.

Having given the action of the earth’s form, mass, and rotation on
the pendulum, there remain the disturbances due to expansion and
contraction, owing to changes of temperature and those of atmospheric
causes. The astronomical points to be observed are somewhat too fully
laid down, but it must be remembered that an exact science requires the
premises to be fully established before a sequence can be drawn.

As the standard of time depends on the passage of a star or the sun, or
any known celestial object, at a certain time across the meridian of
the place where the observation is taken, it was absolutely necessary
to give the modes of calculation, together with the disturbing causes.
Moreover, a full appreciation of the indebtedness of horology to
astronomy could not be obtained without a general knowledge of the
change of the position of the major axis of the orbit described by the
earth around the sun. Also, the difference between mean and apparent
solar time was required to illustrate the use of the tables of equated
time, the necessity of which will become patent when the use of the
transit instrument for the establishment of time, or a fixed standard,
is introduced. Also, the disturbing effects of the sun and moon
collectively and relatively as to position, could not be passed, as
they produce the precession of the equinoxes and the nutation of the
pole--essential elements in the computation of time.




Watch and Chronometer Jewelling.

NUMBER ONE.


This whole subject is well worthy an article both in a scientific and
mechanical sense, whether we consider the delicacy of the operations
or the intractable character of the material operated on--for there
has been no improvement in the horological trade of more importance to
accuracy and durability of time-keepers.

The substitution of stone for common brass or gold bearings, was
prompted by the inevitable wear of the holes from frequent cleaning,
and the abrasion of the pivots, produced by the accumulation of
dust with viscid oil; the pivot being cut away, or the hole opened
too large. So long as the verge and cylinder were the prevailing
escapements, the necessity for jewelling was not so strongly felt,
except in the balance holes. The introduction of the lever escapement
brought with it a better watch,--capable of more accurate time, but
demanding an improved construction.

An Italian, in 1723, first introduced the practice of using stone for
bearings. He not only conceived the idea, but was successful as an
artisan in making his own jewels; ingenious and skilful as he was,
however, he encountered obstacles almost insurmountable.

The art of cutting gems, it is true, was at that time well understood,
but no one had attempted to drill a hole in a hard stone fine enough
for a properly sized pivot. The watches at that time that were jewelled
could boast of nothing more than the balance holes, and they were not
pierced to let the pivot _through_.

It is a very difficult matter to polish a taper indentation in a stone,
even with modern appliances, in consequence of the tendency to create
a _tit_ at the bottom,--thus throwing the balance staff out of upright.
The difficulties in the then state of knowledge retarded the general
introduction of stone-work for many years. The Swiss, however, seeing
the advantages derived, finally struck out the various manipulations
with success. Time and experience gave more skill, and at the present
time it is impossible to find a Swiss watch, even of the cheapest
class, that is not jewelled in at least four holes. The English trade
adopted the art later; but even then it did not become general for many
years. Within a generation, only fine English levers were jewelled.

The mere substitution of a harder substance was not the only
improvement; other conditions necessary to accuracy were insured. The
hole could be made _round_--the material of such a character that no
chemical action could be effected on the oil used for lubrication,
and the vertical section of the hole could be made so as to present
the least amount of frictional surface, yet still giving a perfectly
polished bearing, thus avoiding the cutting of the pivot.

The whole “_modus operandi_” from the stone in the rough to the last
setting up is well worth the attention of the watch repairer, and
certainly that of the manufacturer.

Of the materials used in the trade, the first and most important is
the diamond, used only in the time-piece as an end-stone--but at
the bench all-important, as a means of making the other jewels. The
diamond possesses the requisite susceptibility of polish, combined with
greatest hardness of any substance known; but this adamantine quality
precludes its being pierced with a through hole. Considered chemically,
the diamond is pure carbon,--its different varieties differing only
in structure--common charcoal, its lowest--plumbago, its intermediate
grade. Another variety, called the “black diamond,” or “diamond
carbon,” occurs, which is interesting as being a parallel with emery,
compared with crystallic sapphire. The form of diamond most in use for
mechanical manipulations, is almost always crystallized; yet it will be
seen that the agglomerated form of diamond carbon plays no unimportant
part in jewelling. As a jewel, no use is made of the diamond, other
than as an end-stone. Marine chronometers, in which the balance will
weigh from five to nine pennyweights, are almost invariably furnished
with a diamond end-stone, set in steel. Yet, hard as the substance is,
it is often that a pivot will cut an indentation in its face. The cause
of this apparent anomaly is to be found in the structural character of
the gem, and its value. The lapidary, saving in weight as possible,
does not care, in “Rose Diamonds,” to pay attention to the lines of
cleavage. If the face of the stone makes a slight angle with the
strata of the jewel, there occur innumerable small angles of extreme
thinness--the pivot, coming in contact with any of these thin portions,
may fracture it, and the fragment, becoming imbedded in the tempered
steel pivot, becomes a drilling tool. In our experience we have had
marine chronometers sent for repair, that have lost their rate so much
as to become utterly unreliable from this cause alone--the pivot having
produced an indentation of the stone, creating more friction, and thus
destroying the accuracy of the instrument.

As a general rule, the rose diamonds sold for this purpose are
sufficiently good for general work. In a very fine watch or chronometer
the stone should be selected with reference to its polish on the face,
and its parallelism in the lines of cleavage. The diamond, however,
gets its great importance from being the only agent we can use in
working other stones. Without it the whole art of jewelling would not
be practicable. The various steps are all connected some way with
diamond in its different shapes. “Bort,” the technical name for another
variety, is merely fragments of the stone that have been cleaved off
from a gem in process of cutting, or gems that have been cut, but found
too full of flaws to become of use for ornamental jewelry purposes,
the cost depending on the size, varying from $5.50 to $18 per carat.
This “Bort” is used as turning tools--the larger pieces being selected
and “set” in a brass wire and used on the lathe, in the same manner,
and with the same facility, as the common graver. For tools, even
the diamond is not of equal value--a pure white and crystalline in
structure generally being too brittle (though hard) to endure the
work. Among the workmen the “London smoke,” a clouded, brownish stone,
is most prized--it possessing the twofold qualities of toughness and
hardness.

Another form of “Bort” comes in the shape of a small globule, sometimes
the size of a pea; it is crystallic, and when fractured generally gives
very small, indeed minute pieces of a needle shape. These are carefully
selected, and form the drills with which the English hole-maker
perforates the jewel. These drills, when found perfect, for soundness,
form, and size, are very highly prized by the workman, as the choice of
another, together with the setting, will often take a vast deal of time
and labor.

“Bort” is also used in the making of the laps or mills with which
the jeweller reduces the stones to a condition for the lathe and
subsequent processes. For this purpose such pieces as are not fit for
cutting-tools, or drills, are selected. A copper disk, having been
first surfaced and turned off in the lathe, is placed on a block or
small anvil; each piece of stone is then separately placed on the
copper, and driven in with a smart blow--care being taken that no place
shall occur in the disk that does not present, in revolution, some
cutting point. It would seem impossible to retain the diamond fragment,
but it must be remembered that the copper, being a very ductile metal,
receives the piece; the first rubbing of a hard stone then burnishes
the burred edges of the indentations over every irregular face of the
diamond, leaving only a cutting edge to project. The rapidity with
which such a lap, well charged, will reduce the hardest stone, is
somewhat marvellous. It is the first tool used in jewelling, and so
important that a more detailed and explicit description of its make
will be given when the process of manufacture is treated upon.

Diamond powder is equally as important as “bort,” being used in nearly
every stage of jewel-making. The coarsest charges the “skives” or
saws used for splitting up the stone. These skives are made of soft
sheet-iron, and act on the same principle as the laps. The finer
grades, in bulk, resemble very much ordinary slate-pencil dust;
indeed, the latter is often used as an adulteration. This powder is
not uniform in fineness, and the jewel-maker is under the necessity of
separating the different grades. This is effected by a simple process
called “floating off,” and is conducted as follows: A certain quantity
of powder, say a carat, is put into a pint of pure sweet oil, contained
in some such shallow vessel as a saucer. Depending on the fluidity of
the oil, the mixture, after being thoroughly incorporated, is allowed
to stand undisturbed for about an hour or an hour and a half. During
this time, owing to their greater gravity, the largest particles are
precipitated, leaving held in suspension a powder of nearly uniform
fineness. The mixture is now carefully decanted into another similar
vessel, leaving the coarse powder at the bottom of the first. This
coarse deposit is denominated No. 1, and is used for skives, laps, and
other rough purposes. The decanted mixture in the second vessel is
allowed to remain quiescent for twelve hours, when the same operation
is performed; and the third vessel now contains most of the oil,
together with the finest particles of powder. The precipitate from the
second decantation is the ordinary opening powder; the finest being for
polishing both the holes and outsides of jewels, and giving the final
finish to the faces of pallets, roller pins, locking spring jewels, etc.

The good workman is careful to keep the powder in this condition as
free as possible from any extraneous dust, and above all to preserve
the different grades from any intermixture, as a small quantity of a
coarser grade would destroy a finer one for all its purposes, and the
process of “floating off” would have to be repeated.

The most important stone in jewelling, the diamond, becomes more of an
agent of the manufacture than an object.

Properly, for jewelling the ruby and sapphire are pre-eminent;
inferior only to diamond in hardness, possessing a sufficient degree
of toughness, susceptible of an exquisite polish, this (for they
are one and the same) stone is the favorite of the Swiss, English,
and American, for all high class work--the Swiss, however, using it
indiscriminately in all watches.

The ruby proper is of one color, but in its varieties of intensity
may change to a very light pink. When still lighter it is ranked a
sapphire, which comes in almost every possible color and shade, from
ruby to a perfect transparent colorless crystal. This stone differs
in degrees of hardness and capacity of working--the hardest being a
greenish yellow, in the shape of pebbles, with very slightly rounded
edges, difficult to work, but forming the strongest and most perfect
jewel known.

It must be remembered that this description gives the value of the ruby
and sapphire as a material for jewelling only. For ornamental jewelry,
the value depending on color, of the most intense ruby or blue for
sapphire, together with brilliancy and weight. The ruby and sapphire
are formed on an aluminum base, the common emery being another form of
structural arrangement, but of the same chemical constitution.

These stones possess every quality to make them the base of perfect
jewelling; and still the chrysolite is equally in favor with most
jewellers. It is not quite so hard, but it is more easily worked and
cheaper in price, and it would be difficult to tell wherein it is
inferior to either the ruby or sapphire. It has a yellowish tinge,
verging to the color of the olive. As a stone for jewelry it is not
fashionable, and only in Persia is it valued. There are, however, some
very strong objections to its use by the workman; it is not uniform
in hardness; in polishing it will _drag_, that is, the surface will
tear up in the process. Unfortunately the eye is not able to detect
the fault before working, and it is found only when much preliminary
time and trouble has been expended. It is susceptible, when good, of a
perfect polish, and is much used in chronometer work, especially for
jewelling the 4th hole, as its non-liability to fracture renders it
valuable.

“Aqua Marine” is a brother to the emerald, differing from it only in
intensity of color, and composed of the same constituents. These two
gems are the only ones in which the rare metal, glucinum, has been
detected. It is extensively used in the American and English watches,
but never in the Swiss. It is soft, not much harder than quartz, but
comes in large pieces, perfectly transparent, and of a color which
is that pure green of sea-water, from which it takes its name, “Aqua
Marine.”

The garnet in English watches plays an important part for pallets, also
for roller-pins; a very soft stone, but very porous. When set in the
pallet with a pointed toothed wheel, it is apt to act as a file from
its porosity, cutting the end of the tooth. This may be detected in any
pointed tooth lever watch, by observing the color of the back of the
tooth. “Black vomit” it used to be called in the Boston factory. Most
of the garnet used is an Oriental stone, the best quality coming in
bead form, the holes having been pierced by the natives. The cost of
piercing the stone in Europe or America would be far above its value.
The Oriental is the best for Horological purposes, though Hungary and
Bohemia furnish the most highly prized stones used for ornamental
purposes; indeed, in some German towns the cutting and setting of the
garnet is a specialty, giving employment to a large number of people.
And, strange to say, the best market for their sale is the United
States.

This comprises about all the stones used in watch and chronometer
jewelling. Still in clock work the pallets are generally jewelled in
agate, a stone not at all suited to the purpose, it having, even in
the best specimens, a decided stratification that prevents an uniform
surface being formed by any process. The cornelian form of the agate
is not open to this objection, and makes capital bearings for knife
edges of fine balances, and compass stones for centres of magnetic
needles. For watch or chronometer purposes the only really useful
stones are sapphire, ruby, chrysolite, and aqua marine--all possessing
peculiarities that deserve some remarks, as they are of the utmost
importance to the hole maker. The sapphire is the hardest stone, next
to the diamond, and yet specimens can be, and are found, so soft as
to _drag_ in polishing. Again, if stratified very clearly, will “fire
crack” in opening the hole. The ruby is more uniform in its structure,
and is more highly prized on that account; its hardness being all that
is necessary, while its susceptibility of receiving a high polish
is equal to that of the sapphire or chrysolite. The aqua marine is
always uniform and may be polished both externally and in the hole with
“tripoli,” saving something in diamond powder in the process of making.
In our estimation, however, the chrysolite is the most valuable of all
the stones. True, when purchased in the rough, many pieces will be
found unfit for the jeweller’s purpose; but when the right quality is
found, nothing can be better adapted to jewelling. Hard, it is easily
wrought, taking a peculiar _unctious_ polish, retaining oil in its most
limpid condition for a long time.

These stones form the general stock by and from which jewels are made.
The details of the various manufacturing manipulations, the tools
used, also the setting in the work, together with the important item
of the screws, will form the subject of the next article on Watch and
Chronometer Jewelling. Not having been able to get our engraving done
in time for publication, we are compelled to reserve the remainder for
the next number.




Hints on Clocks and Clock-Making.

NUMBER ONE.


Twenty-five years of hard labor amidst the dust and din of machinery,
with hands cramped, and fingers stiffened by the continual use of
tools, and with a brain constantly occupied in ringing the changes upon
wheels and levers in their almost infinite combinations,--it requires a
degree of courage to undertake to write anything that can be dignified
with the name of an “article,” although it does propose to treat upon
a subject with which we are fairly familiar; but it is consoling to
think that one is not expected to write for the pages of this practical
journal with the same degree of elegance and polish that should grace
the columns of a review or magazine; that we can appear here as plain,
practical mechanics, and use good hard, round words to express our
ideas, backed by an experience which should add some weight--and we
welcome the appearance of the “American Horological Journal,” which
is to serve a good purpose by bringing out the actual experience of
men who have grown gray in the art and mystery of clock-making, and
preserving, by means of the “art preservative of all arts,” their
dearly bought knowledge and experience, for the benefit of those who in
their turn shall follow them; and it will also benefit the people in
general by giving information that will lead to the purchase of good
and tasteful clocks for household use.

That such a journal is needed to enlighten us, is made plain by the
fact that in almost every newspaper we have a vivid account of some
wonderful clock “recently invented,” which may possess some merit, but
they are so grossly exaggerated by some ignorant “penny-a-liner,” that
we are almost led to believe in the Irishman’s marvellous “eight-day
clock, that actually ran three weeks.” Even the proverbially correct
“Scientific American,” of which I am a constant reader, has in its
issue of June 19th, an account in its “editorial summary” of a clock in
France containing “90,000 wheels,” and perhaps the most curious part
of the mechanism is that which gives “the additional day in leap-year,”
etc. Now, it will require but little knowledge of clocks to tell us
that one with 90,000 wheels was never made and never will be, but “the
additional day in leap-year” has been given by calendar clocks in this
country since the year 1853.

It is not proposed in the series of articles to follow, to discuss
the early history of clocks. Reid and Dennison have written enough
to convince the most skeptical that the clock is an old invention.
It is not important to us who invented the pendulum, or this or that
escapement, but who makes the best pendulum, the best escapement, the
most perfect train of wheels and pinions. These are vital points, and
we shall endeavor to give them that attention that their importance
demands. It is proper to state here that any assertion made, or rule
given, has been tested, and is the result merely of our experience,
and we do not claim that it is all there is of the subject; for we are
aware that the experience of others may have led to results entirely
different; but if all clock-makers will avail themselves of the columns
of this journal, we shall not only become better acquainted by an
exchange of ideas, but better clock-makers.

The subject of wheels and pinions is of the greatest importance in
clock-making, and the utmost care and skill are required to execute a
train which shall not only run with as little friction as possible,
but the friction must be equal; for if there is no variation in the
train force, the escapement and pendulum will always be actuated by the
same amount of power, and the performance of the clock can be relied
upon. Clock text-books do not fully impress this subject. We find a
great deal upon this or that escapement, and the different pendulums.
Dennison has a couple of pages full of abstruse calculations upon a
method of shifting an extra weight upon a rod, so that the going of a
clock can be varied one second per day; but if his wheels and pinions
are not perfect, a large tooth here and there will vary the clock more
than that.

Reid overawes us with his knowledge of the proper curves of the teeth
of wheels; but it must have been only theory, for his practice was to
saw his teeth, and his cycloids, epicycloids, and hypocycloids were
left to the mercy of the “topping file” in the hands of his “wheel
teeth finishers,” instead of shaping up the teeth in the engine, as is
done now. We have generally cut the wheels of fine clocks over several
times with different cutters before taking them from the engine; the
last cutter having but one tooth, which can be made perfect as to cut
and shape, and, running with great speed, will leave the teeth the
proper shape, very smooth, and as true as the dial of the engine.
Escape wheels, especially, require great care in cutting, as the
teeth for dead-beat escapements are somewhat long and thin; the least
inaccuracy is certain to cause trouble. It is absolutely necessary that
the dial plate of the cutting engine should be perfectly true, with
clean, round holes, and a perfect fitting index point, with a cutter
arbor without end play or lateral motion--these are the essentials of a
good cutting engine, without which a good clock cannot be made.

We have generally made a practice, upon the completion of the train for
a fine clock, to put in the place of the escape-wheel a very light,
well-balanced fly, to prevent “backlash,” and a very fine soft cord
on the barrel; then hang on a very light weight; so slight that--all
of the wheels being balanced, and no oil upon the pivots--the fly
will move so slowly that its revolutions may be counted. By taking
care that the weight be not too much in excess of the resistance, the
least inaccuracy in the wheels and pinions may be discovered by the
difference in the velocity of the fly, or by its suddenly stopping,
which will be occasioned by any inequality in the train teeth, which
would not have been discovered by the closest scrutiny. It was by means
of this test that we discovered an inaccuracy in a pinion, caused by
hardening, which could not have been discovered by a less delicate test.

The wheels in the train should be as light as possible, for as the
whole train is stopped every time a tooth drops on the pallets, it is
plain that the driving weight must overcome the inertia as well as the
friction of the train at every beat. To this end it has been customary
to “arm out” the wheels, leaving a very light rim supported by light
arms, the wheels being generally of cast brass, turned up, and cut,
then lightened. We followed this plan for some time, but abandoned it,
as we found great difficulty in making a perfectly round wheel. The
arms serve as posts to support the rim in cutting or turning, but the
space between is very apt to spring down. We prefer making the wheels
of fine hard-rolled sheet brass; it is superior to cast brass, much
finer, harder, and more durable, and is freer from flaws. After the
wheels are cut, they are turned out on each side, leaving a thin web in
the centre; they can be made lighter, finished easier, and are round.

As to the shape of the teeth in clock-wheels, the subject has been so
ably treated by Reid, Dennison, and Prof. Willis (who has invented an
instrument to assist in laying out the curves for the teeth of wheels),
that we shall not attempt it in this paper; besides, there is so little
of the entire theory that can be applied to a clock-wheel of two and
a half inches in diameter, with 120 to 140 teeth, farther than to
leave the wheel and pinion of the proper diameter, that we consider it
unnecessary; for if makers of regulators and other fine clocks will
use pinions of 16 or 20 teeth, the friction or driving is all after the
line of centres, and the whole subject of cycloids, epicycloids, and
hypocycloids is reduced to a very small point, and might be said to
“vanish into thin air.”

Having given only a few practical hints, and not yet crossed the
threshold of the subject, we propose to continue from month to
month--if the readers of the JOURNAL do not weary--the discussion of
the various parts that go to make the sum total of a fine clock, with
notices of the various clocks made in this country.

       *       *       *       *       *

It certainly comes within the province, and is the duty, of a journal
devoted to Horology, to make a note of any and all the new improvements
that pertain to the science. We give, then, some few, the merits of
which have struck us as being a very important matter of consideration.

The best clock time-keeper is not absolutely perfect, so its rate must
be kept; but the watchmaker ordinarily has no means of correcting the
error of his regulator, until the accumulation renders it a serious
inconvenience. Did he possess a Transit instrument, properly set and
adjusted for meridian, together with the required books and knowledge
of observing, he could from day to day correct his clock and keep
accurate time; but these are all expensive, as well as involving time
and labor. Suited to the wants of the artisan is a little instrument
called the Dipleidescope; simple in its construction, and not liable
to get out of position or order, it forms the best substitute for the
transit we have seen. It is founded on the theory that the double
reflection from the two surfaces of planes at an angle of 60° will
coincide when the object reflected is in a true line with half the base
of the whole triangle. Having a prism cut in an equilateral triangle,
one angle is set directly down toward the centre of the earth, the base
being brought parallel with the line of the horizon. Now, if the axis
of the prism is in a line with the meridian, a reflection of the sun
will appear, at the instant of crossing the meridian, on itself--that
is, there would be but one image. If the instrument is well made,
there can be no doubt of its accuracy and value to those who, wishing
to verify their time, are not situated so as to use a transit.

Another improvement is a Bench-Key for watchmaker’s use. No one who has
had any experience at the bench but will appreciate an article that
facilitates the setting of time-pieces for his customers. In winding,
it is equally valuable. It is not dependent for its strength of torsion
on the spring-chuck principle, the power being applied close to the
square by means of a pin that passes through the key.

Hall’s Patent Cutting Nippers are a positive desideratum; a large
wire can be cut off without the least jar to the hand, the leverage
is so great. The smallest sizes are suitable to the ordinary run
of watch-work, and can be used in clock-work better than any
cutting-plyers extant. Strong and durable, they possess one quality
that all watchmakers will appreciate--if a cutting-jaw is broken it can
be replaced by another.




Greenwich Observatory.


About two hundred years ago, England began to take a lead in the
mercantile commerce of the world; her ships were daily passing across
the Atlantic, and India also was beginning to attract her attention.
It was therefore of the utmost importance that navigators should be
enabled to find their longitude when at sea, independently of watches
or clocks; and a reward was offered to any one who should discover a
method by which this result might be obtained.

The plan proposed was, that the angular distance of the moon from
certain stars should be calculated beforehand, and published, so that,
for example, it might be stated that at ten minutes and five seconds
past nine on such a day, the moon should be distant from Mars 40
degrees. If from a ship in the middle of the Atlantic, Mars and the
moon were found to be 40 degrees apart, then it would be known that the
time in England was ten minutes and five seconds past nine.

Here, then, was one item ascertained, and the method was a good one;
but in consequence of the want of accuracy as regarded the moon’s
motions, and the exact positions of the stars, it could not be
practically carried out.

Under these circumstances, Charles II. decided that a national
observatory should be built, and an astronomer appointed; and a site
was at once selected for the building. Wren, the architect, selected
Greenwich Park as the most suitable locality, because from thence
vessels passing up and down the Thames might see the time-signals,
and also because there was a commanding view north and south from
the hill selected for the site. The observatory was completed in
1676, and Flamsteed, the chief astronomer, immediately commenced his
observations, but with very imperfect instruments of his own. During
thirty years, Flamsteed labored indefatigably, and formed a valuable
catalogue of stars, and made a vast collection of lunar observations.
He was succeeded by Halley, who carried on similar observations; and
from that time to the present, Greenwich Observatory has been our
head-quarters for astronomical observations.

The work carried on at Greenwich is entirely practical, and consists
in forming a catalogue of stars and planets, and so watching them
that every change in their movements is at once discovered. Now that
this work has been performed for several years, the movements of the
principal celestial bodies have been so accurately determined, that the
_Nautical Almanac_--the official guide on these subjects--is published
four years in advance, and thus we find that on a particular night in
1868, the moon will be at a certain angular distance from a star, and
the second satellite of Jupiter will disappear at a particular instant.
On the exterior wall of the observatory there is a large electric
clock, which, being placed in “contact” with the various other clocks
in the observatory, indicates exact Greenwich time. The face of this
clock shows twenty-four hours, so that it requires that a novice should
look at it twice before comparing his watch. On the left of this clock
are metal bars let into the wall, each of which represents the length
of a standard measure, such as a yard, foot, etc. And let us here say
a few words about these standards. To the uninitiated a yard is simply
three feet, and a foot is twelve inches--an inch being, we are told in
our “Tables,” the length of three barleycorns. Now, as the length of
a barleycorn varies considerably, it requires something more definite
than this to determine our national measures. Thus, the question, what
_is_ a foot? is more difficult to answer than at first sight appears.
Many years ago the French perceived the difficulty appertaining to the
national standard, and they, therefore, decided that a metre should be
the ten-millionth part of one-fourth of the earth’s circumference--that
is, ten-millionth of the distance from the Equator to the Pole. But
here another difficulty was encountered, because different calculators
found this arc of different lengths. By _law_, however, it was decided
that one measurement only was correct, and so the metre was fixed at
3.0794 Paris feet; though since then, more accurate observations and
improved instruments have shown these measured acres to have been
very incorrectly ascertained, and thus the French method failed when
practically tried.

The length of a seconds pendulum oscillating in a certain latitude has
been our method of obtaining a standard; but this also has its weak
points, so that to obtain a constant standard it is necessary to have
some pattern which is unchangeable, and thus a metal has been chosen
that expands or contracts but little either with heat or cold; and
this, at a certain temperature, is _the_ standard measure, and such a
standard may be seen on the exterior wall of Greenwich Observatory.

On entering the doorway--which is guarded by a Greenwich pensioner,
who will possibly first peep at the visitor, in order to see who
the individual may be who is desirous to tread within the sacred
precincts--one finds a court-yard, on the left of which are the
transit-room, the computing-room, and the chronometer-room. The
transit room takes its name from the instrument therein, which is
a large “transit.” This consists of a large telescope, the outside
of which is not unlike a heavy cannon, as it is of solid iron. The
instrument is supported by trunnions, which allow the telescope to be
elevated or depressed to point south or north, and, in fact, to make
a complete revolution, but never to diverge from the north or south
line. The magnifying power of this instrument is not very great, so
that it admits plenty of light, for it is intended, not as a searcher
for or for gazing at celestial objects, but for the purpose of noting
the exact time at which stars and planets pass south or north of
Greenwich. Upon looking through this telescope, the observer’s eye
is first attracted by a vertical row of what seem to be iron bars,
placed at equal distances from each other. These, however, prove to be
only spiders’ webs, and are used for the purpose of taking the time
of passage of a star over each wire, and thus to ascertain the exact
instant of its being in the centre of the telescope. During even the
finest and calmest nights, there is occasionally found a tremulousness
in the instrument, which, as it is rigidly fixed to the walls of the
building, must be due to a slight vibration in the ground itself. Thus,
many a feeble earthquake unfelt by the outsider may be perceived by the
astronomer by the aid of his delicate instruments.

The various stars seem to be travelling at an immense rate when
seen in the field of the transit telescope, and it is really nervous
work noting the exact time when each wire is passed. The experienced
observer, however, not only will give the minute and second, but also
the decimal of a second when the star was on the wire. The result is
obtained by counting the beats of a clock the face of which is opposite
the observer. Thus, if at three the star seems as much short of the
wire as at four it had passed it, then 3.5 might be the instant of
“transit.”

At noon each day the sun’s passage is observed by nearly the whole
staff of observers. One individual looks through the telescope, and
gives the time for each wire, while others examine a variety of
micrometers in order to ascertain the fractional parts of seconds,
etc.,--these micrometers being placed at the side of the instrument.

In the morning, the principal work consists in making what are termed
the “reductions” to the observations of the previous night. These
reductions are the corrections requisite for the slight instrumental
inaccuracy, for the refraction of the atmosphere, and for the known
constant error of the observer. When, therefore, a bright winter’s
night has occurred, the work on the following morning is usually very
heavy. At noon the sun’s time of transit is taken, and at one o’clock
the “ball” is dropped, by means of which the various vessels in the
Docks and in the Thames set their chronometers, or ascertain their
rate. In addition to this, the time is sent by electricity to Deal and
one or two other seaports, in order that every vessel may be able to
know the accurate time, if within sight of those places.

Not the least interesting portion of the observatory is the chronometer
room. For a very small charge, manufacturers or owners may have their
chronometers rated at Greenwich, which is accomplished in the following
manner:

The chronometer is placed in the chronometer room, and compared with
the large electric clock in the room, this clock being kept in order
by the stars. Each day the chronometer is examined, and thus its rate
is ascertained in its then temperature. It is afterwards placed in a
sort of closet warmed by gas, a condition supposed to represent the
tropics, and it is there kept for a certain period, being tested each
day as before. This change of temperature is found to produce very
little effect on the best instruments, which, when they have passed
the ordeal, are returned to the owners with their character ticketed
to them. Some hundred chronometers are often placed in this room; and
to compare them is a science, the “expert” by a glance discovering the
difference between the two instruments, whilst a novice would require
to mentally add or subtract, and thus slowly to arrive at the same
results.

As soon as it becomes dark enough to see stars by the aid of a
telescope, one of the staff commences his observations. These are
continued during the night; and a register is kept of each star,
planet, comet or moon, which is “doctored” in the morning by the
computers.

As all mortals are fallible, it is desirable to bring machinery into
use where possible, and this has been managed in connection with
astronomical observations. Instead of the computer registering by
judgment the time of a star’s transit over the various wires, he
strikes a small indicator, which, completing the electric circuit,
causes a pricker to fall and make a hole in a piece of paper that
is attached to a slowly revolving barrel. Each time the star passes
a wire, the pricker descends and leaves its mark; and the interval
between these marks being measured by scale, the mean time of transit
may be obtained.

There is usually a feeling of the sublime that comes over us when we
reflect upon the vast unexplored regions of space, or contemplate the
stellar world that shines upon us. The magnitude and grandeur of some
of the planets in the solar system strike us with a feeling of awe
and wonder, while we are puzzled at the mysteries attending comets,
double stars, nebulæ, etc. No such feelings or sentiments, however,
are allowed to enter into the constitution or mind of an observer at
Greenwich. Saturn, the glorious ringed planet, with its galaxy of
moons, is simply “Saturn, Right Ascension 10 hours 8 min. 12 sec.,
North declination 16° 12´ 2´´.” Anything appertaining to the physical
constitution, the probable cause of the ring, or the object of so
grand an orb, does not come within the range of the observations at
Greenwich, which are limited to bare matter-of-fact business work.

The southern portion of the observatory ground is devoted to
the investigation of meteorological subjects, and is under the
superintendence of Mr. Glaisher, who is now well known as an aerial
voyager. It is here that an exact record is kept of the amount of
rain that daily falls, of the direction and force of the wind, of
the magnetic changes, of the temperature, amount of ozone, etc.--all
matters which may, and probably will, lead us eventually to the
discovery of some laws connected with the states of weather, and enable
us to predict what may be expected from day to day. Whilst we are now
able to calculate to a few seconds, and for years in advance, the
instant when an eclipse may occur, and to explain the causes of the
various planetary movements, yet we are in a sad state of ignorance
as regards the causes of hurricanes, thunder-storms, continued rains
and droughts; and thus we find that all the would-be prophets who
from time to time spring up and oracularly announce a coming frost
or fine weather, or the reverse, are perpetually meeting with most
signal failures, which, however, does not deter future adventurers from
attempting to gain a cheap temporary renown by trying their luck at a
prophecy.

The perpetual accumulation of facts at Greenwich, whether these be of
an astronomical nature, or appertaining to the air we breathe and its
subtle changes, is a proceeding that must eventually lead us on to a
correct knowledge of the laws which govern these matters, and also keep
us acquainted with any variations that may be occurring in the elements
that surround us.

The order and quietness necessary in such calculations as those carried
on at Greenwich prevent it from being a “show” establishment, and
hence visitors are not admitted except on special business. Then,
however, every aid and assistance are offered to the student and
inquirer; the use of books and instruments is freely given, and such
information supplied as the little spare time of those belonging to the
establishment enables them to afford. Thus a visit to or a period of
study at Greenwich Observatory will amply repay those who wish to gain
the latest and most accurate information on astronomical subjects, or
to practise themselves at the adjustments and use of the instruments;
and to those who have not such opportunity, we offer this slight sketch.

  [_Chambers’ Journal._




Pinions.


Well made as to truth of centring, of division, of form of leaves, and
polish, are, as the trade well knows, of vital importance to the value
of the time-piece.

The making and finishing is one of the most troublesome, as well
as most expensive of all the processes in watch work. The nature
of the material renders it difficult as it approaches so nearly in
hardness to the tools used in cutting. In the ordinary Yankee clock,
the _lantern pinion_ has entirely superseded the solid leaf, which
substitution was the greatest element of success in their cheap
construction. The lantern pinion is really a nearer approximation to
the required anti-frictional form than a majority of cut pinions in
ordinary clocks. In the process of manufacture of the cut variety, the
first consideration is the quality of the steel to be used. For this
purpose it should be carefully selected by trial, thus ascertaining
its fineness, uniformity, softness when annealed, together with its
capacity for taking a good temper, with the least amount of springing
during the hardening process. Very few pinions are cut from the solid
piece--the drawn pinion wire being quite good enough, when milled and
finished, for the ordinary run of watch work.

The steel wire having been selected, the first process is to cut it
up in lengths a trifle larger than the required pinion. The separated
pieces are then centred with care, and having been placed in a lathe,
the staff and pivot are turned up to nearly the required gauge, leaving
a portion of the whole piece the full size for the leaves. They are
now taken to the milling tool to have the proper form given to the
leaves. As this form is of the highest importance, it may be as well to
give here the reasons. Supposing a wheel of 60 teeth, depthing into a
pinion of 8 leaves, it can readily be seen that the arc of the motion
of the wheel tooth is of greater radius than that of the leaf of the
pinion, and it follows that if the teeth and the leaves are made in
taper form with straight sections, there must occur a sliding motion
on the surfaces of both--the power thus absorbed being totally wasted;
but if we curve the surfaces we may approach a form so nearly perfect
that the wheel teeth, being motors, really roll on the leaves, avoiding
almost entirely the friction caused by sliding; the necessity for this
curvature becoming greater the more the wheel exceeds the pinion in
diameter. This curve, which has been demonstrated by very profound
mathematical researches, is the “epicycloidal;” theoretically it should
give no more sliding motion than the surfaces of two plain wheels
revolving on each other. To obtain this perfect form, very great pains
have been taken and expenses incurred, especially by the makers of the
best time-keepers.

In the American factories the cutters are very elaborately made,
the section being an object of great solicitude--it being an exact
counterpart of the space between any two leaves, and also of one-half
the top of the leaf from the curvature to the point, so that in
milling, the space made by the cutter is its shape, leaving the leaf
of the proper form. Generally the pinion passes under two cutters; the
first to strike down the rough stock, the other to dress it to size and
shape, with a light cut. The care and skill required to make these is
certainly very great, and it is a proof of the wonderful ingenuity of
man that they are made so perfect as to shape and cutting power.

A very ingenious device is used for dividing the leaves under the
cutter, which revolves at a moderate speed over a slide, carrying a
pair of centres, between which the turned up piece of pinion wire is
placed. The slide is now pushed up to and under the cutter, and in
its passage as much of a cut is taken as is desirable; in drawing
back the slide the fresh cut space passes under a flat piece of thin
steel, screwed on the frame, and set at a slight angle to the axis of
the centres. On moving the slide towards the cutter for a fresh cut,
the steel plate takes the last cut, and in passing by it the pinion
is turned just as much as the angularity of the plate, which must be
just one leaf. By this very clever device the division is effected
without an index plate. This process, however, is not good enough for
work intended to be very accurate--the pinion wire not being always, or
indeed rarely correctly divided, the original error will be perpetuated
in all the subsequent processes. These are all milled, with oil or soda
water for a lubricator, and it follows that the speed of the cutter is
regulated to get the greatest cut without dulling the tool. When dull,
however, the mill is sharpened on the _face_ of the cutting tooth by
means of small grinders of iron, using Arkansas oil-stone dust for the
first grinding, and giving the necessary delicacy of the edge by means
of crocus, or sharp, followed, when fine work is needed, by rouge.

It is necessary that this care should be taken, for if the edge is
left coarse it will become speedily dulled, and leave a very unequal
and rough surface on the cut of the pinion, which in the subsequent
grinding gives rise to error in shape and size. The pinions, thus cut
to gauge, are dried in sawdust, hardened, and tempered; the staff and
pivots are now turned up to size, and then pass to the polishers. In
the factory they are finished by means of what are called _Wig-Wags_,
which it may be interesting to the reader to have a general description
of.

Two Vs are arranged as centres, the pinion is placed between them,
the circular parts resting in each V, but free to turn on its own
axis. Immediately above the Vs is a frame on which a slide, carrying
the polisher, may traverse--generally about two inches. This slide is
movable vertically so as to accommodate itself to the pinion; attached
to the slide is a connection which leads to a vertical lever, which
is put in motion from a crank on the counter shaft. The grinding is
effected by bringing the grinder, charged with oil-stone dust in oil,
in one of the spaces of the pinion, which, of course, is so arranged
as to bring it parallel and central with the grinder. The power being
applied, the slide takes a very rapid reciprocatory motion, and the
face of the grinder, so charged, rapidly reduces the uneven surface
left by the cutter to what is called the _gray_.

The form of this grinder must be as perfect as the cutters, and the
care taken to get the requisite parallelism is in equal proportion,
and in all the best polishers is planed up while in its position. The
grinder is composed of tin and lead, with sometimes a slight admixture
of antimony, rolled to an even thickness, cut off in suitable lengths,
and then mounted in the carrier of the Wig-Wag to be planed up to
shape. There are too many minute adjustments in the machine to render a
full description in this article admissible. It is large compared with
the work it has to perform, but it is very admirably made, as indeed
all the tools are, in the American factories.

The polishing of the leaves is the next step, and this is effected by
means precisely the same as grinding. In each stage the pinions are
thoroughly cleansed before entering on another. The polisher is made
precisely like the grinder; but instead of oil-stone dust, crocus mixed
with oil is substituted. Owing to the less cutting quality of the
material used, the polisher loses its form sooner than the grinder,
and has to be more frequently reshaped. In very fine work the crocus
is succeeded by fine well-levigated rouge to bring up that jet black
polish, which is considered a mark of quality by chronometer and watch
makers.

With the exception of turning up the staff and pivots, all the work
hitherto described has been expended on the leaves--a very tedious
process, yet done, when the tools and materials are in proper order,
with marvellous rapidity; but tedious as these have been, there are two
others quite as much so before the leaves are finished.

The ends are to be faced--they must be flat (that is a true plane) and
receive the same finish that the leaves took, and is effected by the
wig-wag; only the pinion revolves between centres, at a high speed, the
grinder being brought up to the turned face. Two motions operate--one
rectilinear, the other circular--the result being a compound motion
which prevents the grinder from touching the same spot twice in
succession. To effect this more surely, the operator gives the grinder
a slight vibratory vertical motion. The polishing of the two faces is
effected in the same manner as the grinding; in all cases the cutting
face of the grinders and polishers being kept in a plane perpendicular
to the axis of the pinion, both vertical and horizontal.

The staff and pivots being in the same condition they came from the
lathe, the next step is to grind and polish them. Before, however, we
treat on this process, it may not be amiss to give the general watch
repairer a process by which the facing may be done on a small scale.

As a rule, when the watch repairer has to replace a pinion he selects
one from the material dealer, finished in the leaves, but not on the
ends or faces. The following operations are simple, and any one may
finish these faces with little trouble. Having turned up your pivots
and squared down the face of the leaves with the turning tool, grind
it in the lathe by means of a ring of metal, the inside diameter being
somewhat larger than the diameter of the staff. This ring is held
between two centres, thus allowing it a vibratory motion, so that
when it comes up to the face it accommodates itself to its plane, and
thus has no tendency to force it out of a true flat; the ring, being
larger than the staff or pivot, admits a small lateral motion, enough
to effect a continuous change of surface. The same little tool may be
used for polishing by substituting another polisher and using crocus
and rouge. For the repairer, perhaps on general work the rouge would
be superfluous. Vienna lime, used with a little slip of boxwood,
brings up a very fine and brilliant polish, and in replacing new work
in an injured time-piece, the steel may always be polished with great
rapidity by using the lime on the gray surface left from the oil-stone
dust; being quickly done and affording a very handsome finish.

To resume the consideration of the pinion, the last stage is the
polishing of the circular portions. Here again the wig-wag is the
most useful tool, but it operates somewhat differently, for the
grinder or polisher is pressed down by the finger of the operator,
the pinion being held between the centres of a small lathe attached
to the wig-wag; the staff is first ground and polished as the leaves
have been before, and this is the last operation performed with the
pinion between centres. From this stage it is chucked in a lathe very
peculiarly fitted, the mandrel being hollow; and in it is fitted what
is called a pump-centre, which is movable in direction of the axis of
the mandrel, and capable of being securely fastened at any desired
point. On the nose of the mandrel is secured a hollow steel chuck,
the two sides of which have been filed out, thus leaving an open
space between the end of the pump-centre and the end of the chuck. On
this end a small steel plate, extremely thin, is fastened by means
of shellac, and a hole drilled in the plate capable of taking in the
chamfer on the shoulder of the pivot. The pump-centre being drawn
back, the pinion is introduced into the chuck, the pivot placed in the
hole in the steel plate, and the pump centre is drawn forward until
it forces the chamfer to fill the hole; the pivot projecting from
the chuck is now ready for all the grinding and polishing processes.
Here the wig-wag steps in again, and from the delicacy of the pivots
is modified to suit the case; this is done by having a polisher hung
in the wig-wag on centres, so it may revolve; when in operation one
side of the polisher rests on the pivot, the other on a ruby placed
in a screw, and which screw enables the operative to insure the
parallelism of the pivot. The ends of the pivots are next rounded off
and finished in another set of tools. The pinion is now ready for use,
assuming it to be of the proper gauge. In the American watches the
scape and fourth wheels are generally staked on the staff pinch tight;
the third and centre are staked on the pinion leaves, a rebate having
been turned down on the ends, the wheel set on the shoulder, and the
projecting ends of the leaves riveted down. This has not been designed
as an exhaustive article on pinions; it is merely intended to open the
subject as pursued in the factories. There is much more to be said; and
the various processes on the small scale, as performed by the Swiss
and English, together with their tools, will bear more than a general
description, as they are applicable at any watch bench.

The subject will be continued, in the effort to give a full and useful
article.




New Three-Pin Escapement.


A contributor to the _London Horological Journal_ gives the following
description of his invention:

 “The merit of this escapement is in a newly invented escape-wheel
 which is self-locking and requires no banking pins; the pallets are
 curved inside the impulse and outside the locking, to work with the
 curved points of the teeth of the wheel; being made of gold the wheel
 will go without oil. From its form it has the power of double impulse
 and double locking with the lever. The first takes place at the
 discharge of the escapement, the second does not act unless the watch
 receives a sudden motion, and then the pin or pallet in the roller
 strikes lightly on the lever, when the propellant power drives it back
 again. The balance passes through two turns before the second locking
 takes place, and is formed so as to be able to take up the lever,
 and the watch soon rights itself, and its time will not be affected.
 Another advantage is, that the lever is made of a flat piece of steel,
 as I have introduced a gold stud to receive the ruby impulse stone,
 which is made to adjust easily so as to bring the escapement to the
 closest geometrical accuracy. By its formation this ruby guides the
 impulse to the external edge of the roller notch. These advantages,
 and its simplicity, render it suitable to the best chronometer
 watches.”

A FEW years ago, in 1859 or ’60, Mr. Peabody, a very talented
gentleman of this city, patented a three-pin escapement that performed
extremely well. A full description of his patent and plan is not at
hand, but we will endeavor to give it to our readers in our next issue.




English Opinion of American Watch Manufacture.


In the London circle of Horologists, more attention is paid to the
scientific departments than the mercantile; but for all that, a Mr.
Henry Ganney has held forth before the “British Horological Institute,”
on “American Watch Manufacture.” Though an Englishman, with English
prejudices, he certainly gives a very fair and impartial statement
of the subject; yet he views it almost entirely in the money-making
aspect. He gives all the credit deserved to American enterprise and
ingenuity, and yet there is a certain sense of a drawback. He had
before him samples of machine work; among others, to quote, “several
movements made by the British Watch Company, which flourished and
failed about twenty-five years ago; these were machine-made, and the
perfection and completeness of the machinery they used for producing
these frames has not been equalled, I believe, in America; several
machines being used there to accomplish what was begun and completed by
one here.”

Mr. Ganney is right in his statement, but the example given by the
British Watch Company was the rock seen by the American navigators. One
tool, for facing off, truing up, drilling, depthing, and doing all the
work on the pillar plate, having cost, before completion, some three
thousand pounds sterling, and from its very complexity being utterly
inefficient--worse than useless. In the very inception of the American
watch manufacture a similar mistake was almost made. Experience and
sound reasoning proved, however, that a multiplicity of operations in
any one machine rendered it entirely too complex, the adjustments too
numerous, and the work totally worthless. We shall in another number
refer again to Mr. Ganney’s lecture, and perhaps give some beamings of
light on the early history of the American watch manufacture, derived
from personal observation at the time.




Correspondence.


  EDITORS HOROLOGICAL JOURNAL:

 I received a Prospectus a few days ago advising me of your
 contemplated existence. I could hardly believe the fact; “the news
 was too good to be true.” However, I shall take it for granted, for I
 cannot see why somebody has not before had the enterprise to launch
 out in the periodical line on subjects connected with Horology, the
 field being so extensive and the want so severely felt. Enclosed
 I send you the subscription price; in this much I have accepted
 your invitation, but I also enclose some few lines on a subject not
 particularly practical or theoretical, but very near the truth, and
 may perhaps give you a view of our wants.

 To tell the “plain unvarnished truth,” I am a watch repairer, located
 in a small country village, with a decent stock of tools and a
 moderate trade. In all this I am no exception; so I write this in
 the name of all who are similarly situated. Isolated as we are, we
 (the country village watch repairers) have few means to improve our
 knowledge of the trade, but work on the same old principles learned
 when we were boys and apprentices, and of better and more expeditious
 ways of doing our work we are entirely oblivious. True, our friends
 of the Hebraic persuasion, who, angel like, bring us face to face
 with the outer horological world by selling us material and tools,
 occasionally present to our benumbed vision something new, such as a
 Swiss lathe, or lathes used in the factories; but of what use are they
 to us? We purchase one; well, on the bench it may be an ornament, but
 for use, drilling large holes is the height of our ambition. We have
 not the time to learn by self-experience all the boasted usefulness
 and capacities of the tool; so we go back to our old verge or Jacot
 lathe when we have to put in a pivot or a new staff. We may know all
 about the escapement and be able to detect the cause of any trouble
 with it, but we have no knowledge of the latest modes of repairing the
 injury when it is discovered, and this knowledge is what I hope to
 find in your journal. I live in a section where the general class of
 work is of a very low grade, even the old verge being very common. Our
 stock of material has to be heavy in proportion to our trade, and then
 once in a while we are compelled to send our work to the city, some
 sixty miles distant, in consequence of not being able to do it, either
 from a lack of the material or want of a proper tool. To all intents
 and purposes we remain as stationary as the oyster. Not only do we
 have these vexations, but the ignorance of the public at large as to
 the treatment of their time-keepers is a fruitful source of annoyance;
 we are often charged with fraudulent practices, and a certain degree
 of caution is observed by more than the most ignorant. Thus, a few
 days ago, a stalwart son of the Green Isle made his appearance in
 front of the counter, and, projecting in front of our optics a huge
 English double-cased verge watch, spoke in almost dramatic tones:

 “Plase, sir, av’ ye could make me ticker here go, sir?”

 Answering in the affirmative we reached for the silent “ticker.” He
 drew back with alarm.

 “Bedad, an’ ye’ll not stale a morsle frae this?”

 “Well, but let me see the watch.”

 “An’ will ye let me eyes be on yes all the time?”

 “Yes.”

 “An’ yes’ll not stale a jewil?”

 “No.”

 “Thin, there it is.”

 On looking at the movement the verge was found broken, the injury
 explained, and the price given. He decided on the repairs being done,
 but said, “Give me the watch now and when ye gets the thing fixed its
 meself will come and git it and pay yes.”

 “But we cannot repair the watch without having it.”

 “Faith, thin, ye’ll not have it; ye’ll be taking something frae it.”

 Now, this is an extreme case of ignorance, pardonable, perhaps, in
 this instance, but the public embraces multitudes just as ignorant
 where an allowance cannot be made. I do not expect the JOURNAL to
 reach such cases, or to influence the general mass, but my hope is
 that it will, by raising the general self-respect and tone of the
 repairers, indirectly elevate the respect felt for them by the public
 at large.

 But I am writing too long and rambling a letter. I wish to express my
 hearty wishes for your prosperity. And, in conclusion, will you allow
 me to express a hope that you will give us the knowledge we need--that
 is, post us up on the minutiæ of repairing in the latest styles, the
 newest processes devised, and, above all, give us an article on the
 lathe and its uses?

  Yours truly,
  W. L. C.


We have the pleasure to give our correspondent the assurance that an
expert will contribute to our next number an article interesting as
well as valuable in instruction as to the use of the lathe.




Eclipse of the Sun.


The approaching total eclipse of the sun, on the 7th of August next,
is exciting much interest. The obscuration first occurs in latitude
39° 53´ 3´´ north, longitude 138° 37´ 4´´ west--Washington being the
meridian. The first totality is on the Pacific coast of Siberia, at
sunrise, in lat. 52° 41´ 9´´ north, and long. 165° 26´ 4´´ west. The
eclipse is total at noon in Alaska, lat. 61° 46´ 9´´ north, and long.
68° 4´ 6´´ west. The line of the total eclipse now runs south-easterly,
grazing the coast near Sitka, thence north into British America; then
entering the United States, near the head of Milk River, long. 30° W.;
thence through the south-west corner of Minnesota, diagonally through
Iowa, crosses the Mississippi at Burlington; thence through Illinois,
a little north of Springfield, crosses the Ohio river at or near
Louisville, Ky., passes through the south-west corner of West Virginia,
through North Carolina, just south of Raleigh, ending on the Atlantic
coast at sunset, just north of Beaufort, N. C., in lat. 31° 15´ 2´´
north, and long. 9° 36´ 6´´ east. The line thus described will be that
of totality, only partial in any other part of the United States.

The United States Government is, or has been, establishing a meridian
line at Springfield, partly to make observations on this coming
eclipse, and with the further view of determining a standard of
surveyed lines--all of the Government surveys in Illinois having been
geodetic. Professor Austin, of the Smithsonian Institute, is in charge
of the work, aided by an able corps of assistants.




Diamond-Cutting.


At the Great Exhibition in Paris, in a part of the park contiguous to
the Netherland section, M. Coster, of Amsterdam, has erected a building
wherein all the processes of diamond-cutting are carried on.

The first rough shaping of the more important facets of the brilliants
is here seen performed by the workman, who operates on two diamonds at
once, by bruising each against the other, angle against angle. The dust
that falls from the stones is preserved for the subsequent processes
of grinding and polishing those facets that distinguish the many-sided
brilliant from the dull, original crystal of the diamond. It is used,
mingled with oil, on a flat iron disk, set revolving with vast rapidity
by steam-power, the stone itself being held upon this disk or wheel by
a tool to which it is attached by a mass of fusible metallic alloy,
into which the stone is skilfully inserted. Skill of eye and hand, only
attainable by great practice, is needed for this work; but a skill not
less exact is needed for another process, which may here be seen in
daily operation--the process of cleavage. The diamond, when a blow is
struck on an edged tool placed parallel to one of the octahedral faces
of the crystal, readily splits in that direction. But to recognize the
precise direction on the complex and generally rounded form of the
diamond crystal; to cut a little notch by means of a knife edge of
diamonds formed of one of the slices cleaved from a crystal, and to
cut that notch exactly the right spot; then to plant the steel knife
that is to split the diamond precisely in the right position; finally,
with a smart blow, to effect the cleavage so as to separate neither
too large nor small a portion of the stone--these various steps in the
process need great skill and judgment, and present to the observer
the interesting spectacle which a handicraft dependent on experience
of hand and eye always affords. But Mr. Coster’s exhibition has other
objects of interest. For the first time, we may see here, side by side,
the diamond with the minerals that accompany it in the river beds of
Brazil; and there are even examples in which crystals of diamonds
are included within a mass of quartz crystals, which have all the
appearance of having been formed simultaneously with deposits of the
diamond.

The different districts of Rio and of Bahia are thus represented--the
former producing a confusedly crystallized sort of diamond termed
“bort,” and the latter an opaque black variety; both these kinds being
found associated with the crystallized diamonds used for jewelry.
Though useful in state of powder, the black carbon and “bort” are
incapable of being cut as a jewel.--_“Maskelyne’s Report,” Great
Exhibition._




The Alloys of Aluminum with Copper.


When Sir Humphrey Davy announced the fact that soda, lime, potash,
magnesia, and the other alkalies were but oxides of a metallic base, it
would have been deemed chimerical to have supposed that the discoveries
he made by the expensive aid of the battery would at later date become
of really commercial value. He did obtain both sodium and potassium
in the metallic state. The substances in this form were new to the
chemical world, still more strange to the popular. So new was it to the
chemists, that, on a globule of the reduced sodium being presented to
a very distinguished chemist, he, with some enthusiasm, examined it;
and, admitting the fact of its being a metal, exclaimed, “how heavy
it is!”--when the real fact was that its specific gravity was less
than water; the expression was the result of the general preconceived
opinion that a high specific gravity was a test of a metallic body. It
was reserved for a French chemist, Henry St. Claire Deville, to utilize
the metal sodium, and that, too, in such a manner that the demand
aroused attention to its production;--demand will inevitably bring a
supply.

The original reduction was made by Davy, by means of the voltaic
battery. After it had been proved that these bases were really metals
capable of reduction, chemistry brought all its resources to bear on
the problem, and they were produced by other methods than the battery.
All the processes adopted, however, were too expensive and laborious,
involving an extraordinary amount of complicated manipulations with but
inadequate results. The metal sodium, which is the immediate subject of
our inquiry, long remained an object simply of curiosity or experiment
in the laboratory.

The methods of reducing the metal have of late years been so simplified
that, to quote Prof. Chas. A. Joy in the _Journal of Applied
Chemistry_: “A few years ago a pound of this metal could not have been
purchased for two hundred dollars, and even at that price there were
few manufacturers hardy enough to take the order. At the present time
it can be readily manufactured for seventy-five cents, if not for fifty
cents a pound; and the probabilities are that we shall soon be able to
obtain it for one-quarter of a dollar.”

Deville found that by the reaction of the metallic sodium on common
chloride of aluminum a reduction was effected; the chlorine taking
up the sodium, forming chloride of sodium (common salt), while the
aluminum was left free in the metallic state. It is hardly necessary
to go into the particulars of the process; but a metal well known to
exist, had, for the first time, been brought to the world in such a
condition of structure that its qualities could be tested, not only
chemically, but mechanically. This was the direct result of Deville’s
metallurgic process of obtaining the reducing agent--sodium.

Aluminum in itself would be of but little use, so that a brief
description will be all that is necessary. It is about the color of
silver, but susceptible of a higher polish, especially on a fresh-cut
surface; it is much less susceptible of oxidization than silver; its
specific gravity is but little more than pine wood, and its tenacity,
ductility, and laminating qualities are nearly equal to silver. Its use
in the mechanical arts is limited, notwithstanding all these qualities,
from the fact of its low point of fusibility, and at the heat of
the fusible point being easily oxidized, so much so as to prevent
soldering, except by an autogenous process. But aluminum does possess
a property peculiar to itself--that of forming a purely and strictly
_chemical alloy_ with copper. It unites with it in any proportion;
the compound formed by the addition of 10 per cent. of aluminum to 90
per cent. of copper has been found to possess all the properties of
an entirely new metal, with qualities that render it a very valuable
material in all fine work, such as astronomical instruments; and very
fine machinery, such as watch-lathes, etc.

The French reports on the alloy are somewhat voluminous, but we give
the following.

The color of this bronze so closely resembles that of 18 carat gold,
such as is used for the best jewelry and watch-cases, that it is
capable of receiving the highest polish, and is far superior in beauty
to any gilding.

Samples taken from different parts of the largest castings, when
analyzed, show the most complete uniformity of composition, provided
only that the two metals have originally been properly mixed while in
a state of fusion. These experiments have been made upon cylinders
weighing many hundreds of pounds, and are entirely conclusive.

This valuable quality is not found in any of the more ordinary alloys
of copper. The alloy of copper with tin, for example, known as _gun
metal_, is notoriously subject to a phenomenon known as _liquation_;
in consequence of which a great difference is found in the composition
of the same casting, both in the top as compared with the bottom, and
in the centre as compared with the circumference.

This phenomenon often causes great inconvenience, as the different
parts of large objects will in consequence vary greatly in hardness
as well as in strength. In casting artillery the difficulty becomes a
serious one, and no means have yet been discovered by which it can be
entirely removed.

This homogeneousness of aluminum bronze is a natural consequence of the
great affinity existing between the two metals of which it is composed;
and that there is such an affinity is clearly proved by the phenomenon
attending the manufacture of the alloy. The copper is first melted in
a crucible and the aluminum is then added to it _in ingots_. At first
there is, of course, a reduction of temperature, because the aluminum
in melting absorbs the heat from the melted copper; and this absorption
is so great, in consequence of the great capacity for heat of aluminum,
that a part of the copper may even become solid. But let the mixture
be stirred a moment with an iron bar, and the two metals immediately
unite; and in an instant, although the crucible may have been removed
from the furnace, the temperature of the metals rises to incandescence,
while the mass becomes as fluid as water.

This enormous disengagement of heat, not seen in the preparation of
any other ordinary alloy, indicates, not a simple mixture, but a real
chemical combination of the two metals. The 10 per cent. bronze may
therefore be properly compared to a salt, the more so as it is found by
calculation to contain, within a very minute fraction, four equivalents
of copper to one equivalent of aluminum.

The 10 per cent. bronze may be forged cold, and becomes extremely dense
under the action of the hammer. The blades of dessert-knives are thus
treated in order to give them the requisite hardness and elasticity.
But it has another valuable quality which is found in no other kind
of brass or bronze: it may be forged hot, as well as, if not better
than the very best iron. It thus becomes harder and more rigid, and
its fracture shows a grain similar to that of cast steel. On account
of the hardness of the aluminum bronze, rolling it into sheets would
be a tedious and expensive process, were it not for this property of
being malleable at a red heat. But it may in this manner be rolled into
sheets of any thickness or drawn into wire of any size. It may also be
drawn into tubes of any dimension.

From several experiments made at different times at Paris, it appears
that the breaking weight of the cast bronze varies from 65 to 70
kilogrammes the square millimetre. The same bronze drawn into wire
supported a weight of 90 kilogrammes the square millimetre. The iron
used for suspension bridges, tested in the same manner, did not show an
average of more than 30 kilogrammes. Some experiments were also made by
Mr. Anderson, at the Royal Arsenal at Woolwich, in England, who tested
at the same time the aluminum bronze, the brass used for artillery
and commonly called _gun metal_, and the cast steel made by Krupp in
Prussia. Taking for the maximum strength of the bronze the lowest of
the numbers found as above, we are thus enabled to form the following
table of comparative tenacities:

  Aluminum bronze 10 per cent.       65
  Crupp’s Cast Steel                 53
  Refined Iron                       30
  Brass for cannon                   28

The comparative toughness of these same four metals was also tested in
the following manner: A bar of each was prepared of the same size, and
each bar was then notched with a chisel to precisely the same depth.
The bars were broken separately, upon an anvil, by blows from a hammer.
The last three metals in the table broke each at the first blow, with
a clean and square fracture. The aluminum bronze only began to crack
at the eighth blow, and required a number of additional blows before
the two pieces were entirely separated. And the irregular, torn surface
of the fracture showed the peculiarly tough and fibrous nature of the
metal.

The elasticity of the aluminum bronze was tested by M. Tresca,
Professor at the _Conservatoire des Arts et Métiers_. The experiment
was made upon a bar of simple cast metal, and the following is his
report: “The coefficient of elasticity of the aluminum bronze, the
cast metal, is half that of the best wrought-iron. This coefficient is
double that of brass and four times that of gun metal, under the same
conditions.”

The specific gravity is 7.7, about the same as iron. Another very
valuable quality is presented in the fact that it is acted on by
atmospheric influences less than are silver, brass, or bronze. This
places it in the same rank with gold, platinum and aluminum.

Very stiff and very elastic, tougher than iron, very little acted upon
chemically, and in certain cases not at all, capable of being cast like
ordinary bronze or brass, forged like iron and steel, of being worked
in every way like the most malleable metals or alloys, having, added
to these properties, a color analogous to that of the most precious
metal, this bronze proves itself adapted to uses almost innumerable.
At first sight, it seems difficult to admit that the relatively small
proportions of aluminum which enters into the composition of this
bronze can be sufficient to modify so extraordinarily the properties
of the copper which constitutes so large a portion of its weight. But
we must remember that the specific gravity of aluminum is very low,
and that a given weight of this metal possesses a bulk four times as
large as the same weight in silver. It follows from this that the ten
per cent. of aluminum contained in the bronze equals in bulk forty per
cent. in silver.

The specimens of the ware we have seen, such as spoons, forks, cups,
watch-cases, etc., are certainly very beautiful, having the color and
high polish of gold, while dilute acids do not affect the surface.




On the Reduction of Silver in the Wet Way.


Every chemist is familiar with the reduction of chloride of silver
in the form of powder by means of metallic zinc in the presence of a
little free acid. It is not easy to bring two such substances as the
silver salt and the metal into close contact, and after the work is
accomplished the removal of the excess of zinc has its difficulties.
Dr. Grager suggests a modification of the old method that ought to
be more generally made known. The chloride of silver is dissolved
in ammonia and poured into a well-stopped bottle, and into this is
introduced an excess of metallic zinc, in not too small fragments, so
that any reduced metal adhering to it may be readily washed off.

The decomposition begins immediately, and is rapidly accomplished,
especially if the contents of the flask be well shaken up. Three hours
will suffice to reduce one-quarter of a pound of chloride of silver.
It is easy to ascertain when the reduction is ended, by testing a
portion of the ammoniacal solution with hydrochloric acid. As soon as
no cloudiness or curdy precipitate is formed, the work may be regarded
as completed.

A slight excess of ammonia is said to be favorable. The reduced silver
must be washed with water until all odor of ammonia has disappeared.
The pieces of zinc are removed by pouring the contents of the flask
through a funnel, the opening of which is too narrow for the passage
of the zinc fragments, while the reduced silver can be easily washed
through. The finely divided silver can be digested in hydrochloric
acid to restore it to a pure white color, and it is then ready for
solution or fusion, and will be found to be perfectly pure. In dealing
with large quantities it would be economical to recover a portion of
the ammonia by distillation. In the same way an ammoniacal solution
of nitrate of silver can also be reduced by zinc, and the silver
obtained pure, even when the original solution of the nitrate contains
copper--provided a small quantity of silver be kept in the bath.

It is better where copper is present not to take all of the zinc that
may be requisite for the reduction of the silver. It will prove a
great convenience to be spared the necessity of converting the silver
into the chloride, as it is no easy task to wash out this salt on
filters--and it will be found to be applicable to alloys which do not
contain more than 25 per cent. of silver.--_From Prof. Joy in the
Journal of Applied Chemistry._




Transcriber’s Notes

Obvious errors in punctuation have been fixed.

Page 7: “Mechanique Celeste” changed to “Méchanique Céleste”

Page 12: “ou rexperience” changed to “our experience”

Page 18: “head-quarters far astronomical observations” changed to
“head-quarters for astronomical observations”

Page 22: “it accomodates” changed to “it accommodates”

The Table of Contents lists “Equation of the Time Table” as the article
on page 28. The actual article is named “On the Reduction of Silver in
the Wet Way.” This has intentionally been left as per the original.
Similarly, there is no actual section titled “Notices of New Tools”
despite its inclusion in the Table of Contents, and this has been left
as per the original.



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