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.