WATCH. 
which is the small spring in new pocket- 
watches, underneath the balance. 5. /I he 
pendulum, whose parts are the verge, pal ets, 
cocks, and the bob. 6. The wheels, which 
are the crown-wheel in pocket-pieces, and 
swing-wheel in pendulums, serving to diivc 
the balance or pendulum. 7. The contrate- 
wheel, which is that next the crown-wheel, 
&c. and whose teeth and hoop lie contrary 
to those of other wheels, whence the name. 
8. The great or first wheel, which is that the 
fusee, tkc. immediately drives ; after which 
are the- second wheel, third wheel, &c. 9. 
Lastly, between the frame and dial-plate, is 
the pinion of report, which is that fixed on the 
arbor of the great wheel, and serves to drive 
the dial-wheel, as that serves to carry the 
hand. 
Spring or pendulum watches are pretty 
much upon the same principle with pendulum 
clocks, whence their denomination. If a 
pendulum describing little arches of a circle 
makes vibrations of unequal lengths in equal 
times, it is because it describes the greater 
with a greater velocity. For the same rea- 
son a spring put in motion, and making great- 
er or less vibrations, as it is more or less stiff, 
and as it has a greater or less degree of mo- 
tion given it, performs them nearly in equal 
times. Hence, as the vibrations of the pen- 
dulum had been applied to large clocks, to 
rectify the inequality of their motions, so to 
correct the unequal motions of the balance 
of watches, a spring is added, by the isochron- 
ism of whose vibrations the correction is to be 
effected. 
The spring is usually wound into a spiral, 
that, in the little compass allotted it, it may be 
as long as possible, and may have strength 
enough not to be mastered and dragged about 
by the inequalities of the balance it is to re- 
gulate. The vibrations of the two parts, viz. 
the spring and balance, should be of some 
length, only so adjusted as that the spring, 
being more regular in the length of its vibra- 
tions than the balance, may on occasion com- 
municate its regularity thereto. 
The invention of spring or pocket watches 
is owing to the artists of the present age. It 
is true, we find mention made of a watch pre- 
sented to Charles V. in the history of that 
prince ; but this in all probability was no 
more than a kind of clock to be set on a 
table, some resemblance whereof We have still 
remaining in the antient pieces made before 
the year 1670. 
In effect, it is between Dr. Hooke And 
Mr. Huygens, that the glory of this excel- 
lent invention lies, but to which of them it 
properly belongs, is greatly disputed ; the 
English ascribing it to the former, and the 
French, Dutch, &c. to the latter. Mr. Der- 
ham, in his Artificial Clock-maker, says plain- 
ly that Dr. Hooke was the inventor ; and 
adds, that he contrived various ways of regu- 
lation. One way was with a loadstone. 
Another with a tender straight spring, one 
end whereof played backwards and forwards 
with the balance, so that the balance was to 
the spring as the bob to a pendulum, and the 
spring as the rod of it. A third method 
was with two bidances, of which there were 
divers sorts, some having a spiral spring to 
the balance for a regulator, and others with- 
out. But the way that prevailed and con- 
tinues in mode,’ was with one balance, and 
one spring running round the upper part of 
the verge ; though this has a disadvantage 
which those of two springs, &c. were free 
from, in that a sudden jerk or confused 
shake will alter its vibrations, and put it in an 
unusual hurry. 
We shall conclude this article with an ac- 
count of the mechanism of a common pocket- 
watch. 
The Plate Watch-work, explains the con- 
struction of a common pocket-watch. The 
moving power is a spiral steel spring (fig. 3), 
which is coiled up close by a tool used for 
the purpose, and put into a brass box (fig. 2) 
called the barrel : the spring has a hook at 
its outer end which is put through a hole in 
the side of the barrel and riveted ; the inner 
end has an oblong opening cut through it, to 
receive a hook upon the barrel arbor (fig. 6) ; 
this arbor goes through the bottom of the 
barrel, and is square to hold a worm-wheel 
d, (fig. 5) which is turned round by a worm 
b; the ends of the arbor project below this, 
and it is pivoted into the lower plate A (fig. 
8) of the watch : the top of the barrel has a 
cover put over it, through which the pivot of 
the arbor projects, and works in a socket in 
the upper plate D. 
The barrel thus mounted has a steel chain 
a, (figs. 1 and 8) hooked to its upper end, 
and coiled round it ; the other end of this 
chain is hooked to the lower part of the fusee 
E (figs. 1 and 8). It is evident that when 
the fusee is turned by the watch-key, it will 
wind the chain off the barrel on itself; and as 
one end of the spring is fastened to the barrel, 
and the other is hooked to the arbor (which 
is prevented from turning by the worm-wheel 
beneath), the spring wiil be coiled up into a 
smaller compass than it was before, and by 
its re-action will, when the watch-key is taken 
off", turn the fusee and keep the watch going. 
The fusee has a spiral groove cut round it, as 
shewn in fig. 4, in which the chain lies: this 
groove is cut by an engine, so that the chain 
shall poll from the smallest part of the fusee, 
when the spring is wound up, and act with 
its greatest force ; and gradually increases in 
size as the spring unwinds and acts with less 
power, so that the effect upon the great wheel 
e (figs. 1, 8, and 7) may be always the same, 
and cause the watch to go with regularity ; 
and this effect can be at any time increased or 
diminished by turning the worm h, (fig. 5) 
which coils line spring up closer, and causes it 
to act with greater force, or vice versa. 
The fusee (fig. 4) lias a ratchet wheel, 
at its lower end, which takes into a click fixed 
in a hollow cut in the great wheel (fig. 7), in 
order that when the watch is winding up, the 
fusee may slip round without the great wheel; 
and that when the spring draws it round in 
the other direction, it may move the great 
wheel with it, and the other wheels of the 
watch. The great wheel e, has 48 teeth on 
its circumference, which take into and turn a 
pinion of 12 teeth, fixed on the same arbor 
with the centre wheel g, and fig. 9, which has 
54 teeth to turn a pinion of six leaves on the 
arbor of the third wheel h, and fig. 10; the 
third wheel has 48 teeth, and turns a pinion of 
six on the arbor of the contrate wheel i, and 
fig. 11, which has 48 teeth cut parallel to its 
axis, by which it turns a pinion of six leaves, 
fixed to the balance-wheel k, fig. 8, 12, and 
14. The pivots of the arbor of this wheel 
turn, one in a frame F, (fig. 8, and fig, 15) 
&3L 
called the pottance, fixed to the upper plate ; 
and the other in a small piece fixed to the 
upper part, called the counter-pottance, so 
that when the two plates are put together, the 
balance-wheel pinion may work into the 
teeth of the contrate week 1 he balance 
wheel has 15 teeth, by which it impels the 
balance /, (figs. 8 and 1 6, and fig. 13); the 
arbor of the balance, which is called the 
verge, has two pallets projecting from it near- 
ly at right angles to each other; these are 
acted upon by the balance wheel, as shewn in 
tig. 14, where the lower pallet is supposed to 
be in contact with one of the teeth of the 
balance wheel, which, as it turns round, 
pushes the pallet round and the balance with 
it, till the balance has made about a quarter 
of a turn : the tooth of the balance wheel then 
slips off and escapes ; in this position the 
watch would run down if it were not for the 
upper pallet at that instant taking another 
tooth on the opposite side of the balance 
wheel, which, as it moves in a contrary di- 
rection, pushes the balance back again, till 
the tooth escapes the pallet ; the lower pallet 
then engages the wheel as before. But tor 
the better regulation of the time, the balance 
has a very fine spring m (fig. 16), called the 
pendulum spring, with the inner end fixed to 
the verge just beneath the balance, and the 
outer end pinned to a stud fixed to the top 
of the upper plate of the watch, so that the 
balance will rest only in one position, and if 
it is moved either way by the balance wheel, 
the spring will have a tendency to bring it to • 
the same position again. When the lower 
pallet, for instance, has just liberated a tooth 
of the balance wheel, the pendulum spring is 
strained, and returns the balance to its point 
of rest instantaneously, the balance wheel 
following the upper pallet by the action cl the 
main spring; and when the balance wheel 
comes to push the balance beyond its point 
of rest the other way, it moves slowly, be- 
cause it has the elasticity of the pendulum . 
spring to overcome. 
It is evident that by strengthening or weak- 
ening this spring, the velocity ot the balance 
can be regulated, which is done by a con- 
trivance shewn in fig. 1(5, and the under side 
of it in fig. 17. It is a plate of brass screwed 
to the top of the upper plate, close under the 
balance ; and at one place it is hollowed out 
to receive a wheel n, of 20 teeth, winch turns 
a segment of a wheel p, called the curb, 
which moves round in a circular groove: it 
has a projecting leat q, with a notch in it to 
receive the pendulum spring; so that by turn- 
ing the wheel with a key put on a square part 
of its arbor, the spring is lengthened or short- 
ened, so as to give it a different power, and 
make the balance vibrate quicker or slower ; 
the arbor of the wheel n, has a dial r, (fig. 16 ) 
upon it, with divisions to set it by. I he upper 
pivot of the verge runs in a cock screwed to 
the upper plate, as shewn in fig. 8, which 
covers the balance and protects it from vio- 
lence ; and the lower pivot works in t he bot- 
tom of the pottance; the socket for the pivot 
of the balance wheel is made in a small p : ece 
of brass, which slides in a groove made in 
the pottance, as shewn in fig. 15, so that by 
drawing the slide in or. out, the teeth of the 
balance wheel shall just clear one pallet be- 
fore it takes the other. 
The watch is so adjusted by the pendulum 
spring, that the balance shall vibrate so as to 
