approaches the chronometer; it is probable that it was originally
invented by Dr Hooke, although, as we now have it, it came from the
hands of Tyrer. It is seen in our illustration. A, the escape-wheel; B,
the escape-wheel teeth; C, the balance; D, the pallet of impulse; E, the
ruby roller; F, a notch in ditto: 1, 2, 3, cogs or upright teeth on the
rim of the escape-wheel. The balance is supposed to be turning downwards
towards the right, the tooth of the escape-wheel just resting against
the ruby roller. When this (which is called the return) vibration is
complete, the balance, by the strength of the hair spring, is carried in
the opposite direction, and as the notch F passes the tooth of the
escape-wheel, this latter is enabled to pass the roller, and the upright
tooth or cog falls upon the pallet D, and thus gives impulse to the
balance. The next straight tooth of the escape-wheel is now resting
against the roller _e_, and the same operation again takes place. This
escapement is much superior to the horizontal, and is almost independent
of oil. It can carry a balance of much greater weight, and when well
made performs admirably. Duplex watches, however, should never be
selected by persons who are accustomed to ride on horseback, as these
instruments are liable to be affected by any sudden motion. Even the
stepping quickly from a vehicle may stop them, and yet the escapement be
as perfect as possible. They are only adapted for persons of very quiet
habits. Thomas Mudge, in the year 1766, introduced an admirable
invention, which, after many alterations and improvements, is now
universally known as the '_Patent Detached Lever_' escapement,
represented by--_a a_ the escapement-wheel, _b b_ the ruby pallets, _c_
the lever, _d_ the balance. On the axis of the balance _d_, towards the
lever _c_, is a small disc of steel, into which is inserted a small pin
made of ruby. This pin fits with great nicety into a notch or opening in
the end of the lever _c_, upon which are firmly fixed the two pallets _b
b_, into which are secured rubies very finely polished. The balance in
its vibration on either side, carrying with it the steel disc and ruby
pin, causes that pin to enter the notch in the lever and carry the lever
with it, and at the same time, to draw the pallet from the tooth of the
escapement-wheel _a_. Power being exerted upon this wheel by the
mainspring, the wheel tooth gets disengaged from the locking-face of the
pallet, forces itself down the slopes of the pallet, and thus gives
impulse to the balance. At each vibration the same unlocking takes
place, but as soon as the wheel tooth falls from the slope, the opposite
pallet is prepared to receive the advancing tooth of the
escapement-wheel, and so on in succession beat after beat takes place.
So excellent was this escapement considered a few years back, that
chronometers were made upon the principle, and placed in the Royal
Observatory for public trial. But since then many improvements have been
made in it, so that makers are now enabled to produce a pocket watch,
with the short angle lever escapement, which marks time at a steady rate
of within four or five seconds weekly,--a rate which approaches so near
to the time-keeping of a pocket chronometer, that unless the minutest
exactness for some specific purpose is required, the last-named watch is
all that can be wished for.
+----------------------------------------------------------------------+
| [Illustration: Lever Escapement.] |
| |
| [Illustration: Chronometer Escapement.] |
+----------------------------------------------------------------------+
About the year 1780 was invented the escapement which is now denominated
the Detached or _Chronometer Escapement_ (see opposite page), the
principles of which are the nearest approach to perfection, the impulse
to the balance being given at the centre of vibration. A is the
escape-wheel, B the escape-wheel teeth, C the roller let on the verge,
or axis of the balance. This roller is a circle of polished steel, with
a notch cut out of it, into one side of which, D, a flat polished piece
of ruby is inserted for the acting part. Below this steel roller,
carried on the same verge, is a smaller roller of steel (E),
denominated the discharging pallet, having a sapphire fixed on its outer
edge. F is a slender spring, which is screwed at I to the stouter one,
having its fixture at the stud L, and polished away very thin at K, in
order that it may bend readily, so as to cause very little resistance to
the balance while forcing it on one side. G is a projecting piece,
carrying an upright pin made of ruby, against which the wheel tooth B
rests; at B is a small screw against which the spring L K G strikes, and
thus prevents it from springing too far back. The action of these parts
is as follows:--When at rest the circular edge of C is just clear of the
two teeth of the wheel B, which cannot be set in motion while E and G
remain quiescent; G rests against the screw at B, and the tooth resting
against the locking pallet G, the escapement-wheel cannot turn. To set
the chronometer going it is necessary to give it a rotary motion, which
sets the balance in action. This causes the lower piece on the verge
(called the lifting piece or discharging pallet) to strike against the
end of the spring F, which, from its over-lapping the curved end of the
prolonged spring K G, pushes it back, and thus releases the pin or
locking stone G from before the tooth of the wheel: that is, it unlocks
the escapement-wheel, which is immediately set in motion by the force
of the mainspring. The same vibration given to balance and verge brings
the ruby pallet D round before the tooth B, which strikes against it and
carries it round. The recoil of the spring F has now brought the locking
pallet G to catch the tooth B, the escapement-wheel is thus again
stopped. But the stroke of the tooth upon the face of the ruby pallet D
has driven the balance on in its vibration till it is counteracted by
the tension of the balance spring, which brings it back again; in this
return vibration the lifting pallet E, by its curved back, pushes the
slender spring F before it, and passes it without affecting K, G, which
is stiff enough to remain unmoved by F, even when this strikes and rests
against it in recoiling. The wheel, therefore, continues locked on the
upright pallet G, and the vibration proceeds uncontrolled till the great
pallet is again brought round, and the balance spring again checks the
vibration, the above process being repeated. In this escapement,
consequently, part of one vibration in one direction, and the whole of
that in the other, is performed without the balance being in any way
under the influence of the motive power; while the parts are so
contrived that the impulse given by the tooth of the escape-wheel,
affects in a very slight degree the natural motion of the balance. It
can be easily understood that the lifting pallet E can pass the spring F
in one direction without moving K and G, while in the other it carries E
and G with it.
+----------------------------------------------------------------------+
| [Illustration: Compensation Balance.] |
+----------------------------------------------------------------------+
Several appliances have been from time to time introduced to correct
the error in time-keeping caused by variations in the temperature, but
none have come into such general use as that known by the term
'_Compensation Balance_,' invented by Thomas Earnshaw, of London, and
for which he received a government reward. This balance, when properly
adjusted, causes the watch to keep the same time whether the
temperature be 32 deg. or 90 deg.; while without it a watch will show
a considerable difference in time, on being merely transferred from
the pocket to the dressing-table, where, probably, the temperature
would not be so high. Our woodcut represents a balance of this kind;
the divided rim A A, is composed of steel and brass run together by
fusion, the more expansible metal, brass, being placed outwards, the
result of which is as follows:--Heat elongates the pendulum spring,
and thereby causes a slower vibration of the balance. The same amount
of heat will also expand the metals composing the balance; but as the
inner rim of steel does not expand so freely as the outer one of
brass, the conflicting action of the two tends to draw the free end of
the circular rim inwards towards its centre, and thus decreases in all
but one direction the diameter of the balance. This decrease tends to
_quicken_ its vibration, and thus counteracts the effect of the
elongation of the pendulum spring. In cold temperatures the pendulum
spring is contracted, making the vibrations quicker, but the
contraction of the brass rim draws the free end outwards, thus
increasing its diameter, retarding its vibrations, and counteracting
the effect of the contraction of the pendulum spring.
Many contrivances have been introduced to test the equality of
compensation balances, but the majority have been abandoned from the
circumstance that the heat was not equally distributed to the watches
under trial. In pursuance of this object, an oven was invented, heated
by hot water, which answers the desired end. It is an apparatus made
of copper, two feet high, thirteen inches broad, and eight inches
deep. From the top to the bottom, at the distance of fifteen inches,
it is divided into two compartments. All around the upper one (except
the front, which has a glass door through which the chronometers and
watches are seen without opening it) is one inch of water. It has a
chamber thirteen inches high, eleven inches broad, and seven inches
deep for the reception of chronometers and watches. The water is
introduced at the top in the same manner as a solar lamp is supplied
with oil. The bottom compartment contains a jet of gas, which can at
pleasure be regulated so as to keep the watch at any required
temperature. The heat radiated from the inner surface of the
chronometer chamber is thus equally distributed among the instruments
under trial. A thermometer placed within the upper chamber indicates
the temperature, and by this simple apparatus a watch can be regulated
with the greatest nicety to suit the particular climate into which it
may be taken.
The DIAL AND HANDS should be sufficiently in contrast one to the other
to show the time at a glance. Dials are sometimes made of gold or
silver, but these are not so distinctly seen as white enamelled dials,
with black figures or numerals, and dark blue steel hands; the
enamelled faces, although, perhaps, more brittle than gold or silver
dials, are therefore in greatest request. Up to a comparatively recent
date the seconds' hand was placed upon the level face of the watch,
but sunk seconds are now everywhere in use, even in the cheaper sorts
of watches. The chief objection taken to the sunk seconds is that it
disfigures the dial by breaking the uniformity of the numeral letters,
the VI being of course obliterated to make room for it, but this
obliteration seems of smaller consequence than the confusion which may
arise from the use of longer seconds' hands and their being at any
time mistaken for that of the hour or minute.
The JEWELLING of a watch is an important part of its manufacture,
inasmuch as it is by means of jewels that durability is chiefly
secured. Watch pivots would rapidly wear out the metal in those parts
in which there is continual friction, and jewelling has therefore
become general. The watch-maker uses for his best watches a peculiarly
hard kind of ruby, which has been known to withstand the wear and tear
of the best part of a century without showing symptoms of yielding,
whereas inferior jewels are perhaps scarcely so hard as the best
tempered metal.
The FRAME, usually of brass gilt, sustains both ends of each axis, and
is now principally designed to fit a full-plate movement or a
three-quarter-plate movement. The former is undoubtedly the more simple
construction, but with considerable disadvantage in taking to pieces the
watch and putting it together again when repairs are needed. The
examination of the escapement in a full-plate watch, and the cleaning,
or altering, or oiling which may be needed, cannot be done without
taking the whole movement to pieces. The three-quarter-plate movement is
not only preferable on account of its superiority in respect to
solidity, and the economy of labour in its manufacture, but from its
being flatter than the full-plate watch, and allowing of repairs being
more easily made.
The WATCH-CASE, which used to be of various materials, such as
tortoiseshell, pinchbeck, or one of the precious metals, is now almost
universally of gold or silver. Silver cases are invariably of the
standard required by the law and stamped accordingly; gold cases vary in
fineness,--some being made and stamped of 9 carat gold, but the best
for wear, and as such preferred by the best makers, are of 18 carats,
and are stamped as such with the hall mark, usually in three or four
places,--on the bow, the pendant, and the inside of the case. Much
depends upon the care with which this part of a watch is finished, for
an ill-fitting case admits dust which renders frequent cleaning
necessary, and prevents accurate time-keeping. After the casemaker has
constructed the case it has to pass through several hands before it is
completed,--for instance, it is one man's work to fit the works to the
case by making the joint at the 12 o'clock and the bolt at 6 o'clock,
and to supply the wheels to propel the hands; it is another's to perform
the part of engine turner, and to mark the case with those curiously
intricate lines whose wonderful precision cannot be secured by mere
hand-work, but by a combination of mechanical and human labour;
another's to finish the joints, or, as the uninitiate would perhaps call
them, the hinges; and last of all the fitter of the case with springs,
and polisher to give the necessary finish. In the same way has each part
of the mechanism of the interior passed through a series of workmen's
hands. Nearly every wheel and pinion has been separately made by men
whose entire time is given to the perfecting of their several branches
of labour, the subdivisions of which and their ramifications would need
many lengthy chapters of description, to do them justice. The
escapement is of itself a distinct department requiring a number of
co-operating hands, from those which first shape the metal to the
balance-maker working in brass, steel, or gold, and the final adjustment
of the escapement-maker. The chain, the spring, the jewelling, the
brass-work, the engraving, the gilding, have each their separate
history, some of them being brought from one district and some from
another, to be put together in the watch manufactory, which is finally
to produce them unitedly as an entire watch. Division of labour provides
a larger amount of skilled work, and a more satisfactory result, than
any other method. The workman whose entire life is spent in making the
head of a pin or in fixing it on, will do his work better than the man,
however clever he may be, who should attempt to make the whole pin; and
not only is the work thus better done, but it is done by combination
much more expeditiously and cheaply. All that the watch-manufacturer can
do by way of choosing his materials is, however, of course, but
antecedent to his own work of actual construction, of finishing,
examining, and regulating. He is to the watch what the architect is to a
house; the latter is none the less the rearer of the structure because
he did not himself make the bricks, or saw the timber, or mix the
mortar. Each subordinate brings certain materials to the hand of the
constructor, and he combines them, and gives them their places, he
turns them into shape and produces them as a perfect whole. So the
watch-manufacturer, instead of going himself back through the various
stages of work which in Nuremberg-egg time had, perhaps, all to be done
by one pair of hands, chooses, adapts, combines the labours of hundreds
of busy collaborateurs, all of whom have made portions and pieces,--he
alone makes the Watch.
COMPLICATED WATCHES are so called because besides the ordinary watch
movement they possess other mechanism more or less complicated, by
means of which they can indicate special portions of time,--as for
instance the _Chronograph_, which marks on its dial the fifth of a
second; the _Quarter_, and _Half-Quarter_, and _Minute Repeaters_,
which furnish the time in the dark to within a minute, and are
invaluable to invalids and blind persons; the _Clock-Watch_, which
strikes the hours even in the pocket; the _Clock-Watch Repeater_,
which strikes and repeats; the _Independent split Centre Seconds, and
Fifth Seconds Watch_, which shows (by comparing the one with the
other) the lapse of time to the fifth of a second; the _Perpetual
Calendar Watch_, which shows the day of the week and of the month, the
name of the month, the phases of the moon, &c.; the _Perpetual
Calendar Repeating Watch_, which in addition to the calendar shows by
a repeater the hour, quarter, and minute; and the _Meridian Watch_,
which shows the time of day in any given number of places in any part
of the world. A few words descriptive of the peculiarities of each of
the above complicated watches will be necessary here, and observing
the sequence as above, the following brief particulars will perhaps be
sufficient for ordinary reference, or for being kept in memory.
+----------------------------------------------------------------------+
| [Illustration: Complicated Watches.] |
+----------------------------------------------------------------------+
The CHRONOGRAPH is undoubtedly the most perfect instrument yet
invented for marking the exact time occupied by certain rapid
movements or events or performances,--and is therefore well adapted
for astronomical and medical observations, for timing machinery, for
indicating the speed of a race, and of similar quick events even to
the tenth of a second. It consists of an ordinary quick train lever
movement on a scale sufficiently large to carry the hands for an
8-inch dial. The peculiar feature of the chronograph is its second
hand, which is double, consisting of two distinct hands,--the one
lying over the other. The lower of the two is furnished at the tip
with a small reservoir having an extremely small orifice below; over
this orifice the point of the upper hand is bent so as to fall exactly
upon the puncture, and to convey through it, as with a pen, the ink
held in the reservoir. The mode of operating with the chronograph at a
race has been thus described. 'The chronograph is held firmly in the
left hand of the operator, who watches the starters, but need not
trouble himself to keep at the same time an eye upon the dial. At the
moment of the start he presses the finger or thumb of his right hand
gently upon the button of the pendant, and instantly a black dot is
deposited on the dial, and--the operator being ready to touch the
button at the precise moment of the finish, and thus to complete what
we may call the chronogram of the event--the exact length of the race
is registered, even to a decimal fraction of a second, and an
indisputable record written by the instrument itself in black and
white. The chronograph, it should be mentioned is, apart from its
chronographic mechanism, an excellent time-keeper, and may be worn as
an ordinary watch, being the same size as a gentleman's lever watch.
REPEATING WATCHES are now made so as to require no key. They are
constructed with a lever or chronometer escapement, and are known
according to their method of repeating,--the ordinary _Repeater_
strikes the hours and quarters,--the _Half-quarter Repeater_ strikes
the hours, quarters, and half-quarters,--the _Minute Repeater_ strikes
hours, quarters, and minutes. The first tells the time in the dark or
to the blind person to within a quarter of an hour, the second tells
it within seven minutes and a half, the third tells it to the minute.
The CLOCK WATCH and CLOCK REPEATING WATCH are also made so as to need
no key. They strike the hours and quarters while being worn in the
pocket, and have not only the two trains of wheels for going and
striking as in a clock, but a third train provided for repeating
purposes. Both mainsprings are wound up by the same winder by a
forward and backward action of the pendant. They are constructed with
either Lever, Duplex, or Chronometer Escapements, and some are
provided with compensation balances adjusted to act equally at
extremes of temperature.
THE INDEPENDENT CENTRE SECONDS WATCH is peculiarly adapted for the use
of the medical profession. By means of its two trains it carries,
besides the ordinary hands denoting hours, minutes, and seconds, a
long seconds hand which can be stopped without stopping the watch. It
is made with a stem winder, and therefore requires no key.
THE SPLIT CENTRE SECONDS is not quite so complicated as the last
named. It has two centre second hands revolving round the dial, the
one directly over the other, as also, in another part of the dial, a
small hand revolving five times in a second. Upon pressing a
stop-piece one of the long second hands is stopped, and another
pressure will stop the other--the space between the two hands will
then indicate precisely the time occupied by the event which it is
desired to measure. Another push to the stop-piece will make both
hands again fly together, and enable the operator it may be to make a
new experiment or observation.
+----------------------------------------------------------------------+
| [Illustration: The Perpetual Calendar Keyless Watch.] |
+----------------------------------------------------------------------+
THE PERPETUAL CALENDAR KEYLESS WATCH, shows on its dial the year, the
month of the year, the day of the month, the day of the week, the phases
of the moon, as well as hours, minutes, and seconds. It requires no
setting, as the old-fashioned Calendar Watch did at certain intervals,
but, by a very ingenious contrivance, the changes from month to month,
as for example from February 28th to the 1st of March, or from 30th or
31st of other months to the 1st of the next, are all performed by the
watch, which also of itself marks the extra day for Leap Year. When to
all the above are added, as is sometimes done, the Minute Repeating Work
to repeat the hours, quarters, and minutes, it may be said that the
power of complication can no farther go within the limits of the small
box which is called a watch case,--for these watches are provided with
either Lever, Duplex, or Chronometer Escapements as may be preferred,
and with compensation balances adjusted to serve in extremes of
temperature. But in the examples set forth in the following
illustrations, it will be seen that superadded to all the foregoing are
a thermometer, and an index showing the calendar by the old and new
style, as indicated by the words Gregorian and Russian,--the former
referring to Pope Gregory who decreed the alteration to the new style,
and the latter to the fact that the Russians still reckon by the old
style.
+----------------------------------------------------------------------+
| [Illustration: Perpetual Calendar.] |
+----------------------------------------------------------------------+