y the pinion e, makes 12 revolutions for one 
i the wheel E: and the pinion /makes 10 
■evolutions for one of the wheel F ; conse- 
faently the pinion/ performs 10 times 12 or 
120 revolutions in the time the wheel E per- 
forms one. Hut the wheel G, whicn is turned 
ly pinion /, occasions 6() vibrations in the 
pendulum each time it turns round ; conse- 
quently the wheel G occasions 60 times 120 
br 7200 vibrations of the pendulum while the 
L heel E performs one revolution ; but 7200 is 
(the number of vibrations made by the pendu- 
lum in an hour ; and consecjuently the v. heel E 
performs but one revolution in an hour, and so 
of the rest. From this reasoning, it is easy to 
discover how a clock may be made to go for 
any length of time without being woundup: 
I .' By increasing the number of teeth in the 
wheels ; 2. By diminishing the number ot 
teeth in the pinions; 3. By increasing the 
length of the cord that suspends the weight ; 
4. Bv increasing the length of the pendulum ; 
and, 5. By adding to the number of wheels 
and pinions. But, in proportion as the time 
is augmented, it the weight continues the 
same, the force which it communicates to the 
last wheel, G H, will be diminished. It only 
remains to take notice of the number of teeth 
in the wheels which turn the hour and minute 
hands. The wheel E performs one revolu- 
tion in an hour; the wheel N N , which is 
turned by the axis of the wheel E, must like- 
wise make one revolution in the same time ; 
and the minute-hand is lixed to the socket ol 
this wheel The wheel 2s has 30 teeth, and 
pets upon the wheel O, wmc.h has likewise 
30 teeth, and the same diameter; conse- 
quently the wheel O rakes one hour to a revo- 
lution : now the wheel O carries the pinion p, 
[which has 5 teeth, and which acts upon the 
wheel qa~ of 72 teeth; consequently the pi- 
nion p makes 12 revolutions, while the wheel 
\qq makes one ; and of course the wheel qq 
jtakes 12 hours to oue revolution, and upon 
the socket of this wheel the hour-hand is 
fixed. All tint has been said here concern- 
ling the revolutions of the wheels, &c. of 
{clocks, is equally applicable to the general 
movements of watches. 
Dr. Frankliir contrived a clock to show the 
hours, minutes, and seconds, with only three 
wheels and two pinions in the whole move- 
jment. The dial -plate, lig. 3. has the hours 
[engraved upon it in spiral spaces along two 
[diameters of a circle containing four times 
60 minutes. The index A goes round in 4 
[hours, and counts the minutes from any 
[hour which it has passed to the next fol- 
lowing hour. The time, therefore, in the 
j position of the index shown in the figure, is 
' either 30 minutes past XII, l V> or \ III ; and 
j so in every other quarter of the circle it points 
to the number of minutes after the hours 
which the index last left in its motion. The 
small hand B, in the arch at top, goes round 
once in a minute, and shews the seconds. 
The wheel-work of this clock may be seen in 
fig. 4. A is the first or great wheel con- 
; tinning 160 teeth, and going round in four 
I hours with the index A in fig. 3 let down by a 
hole on it axis. The wheel turns a pinion of 
10 leaves, which therefore goes round in a 
quarter of an hour. On the axis of this pi- 
nion is the wheel C of 120 teeth ; which goes 
round in the same time, and turns a pinion 
D of 8 leaves round iu a minute, with the se- 
qpnd-haud B of fig. 3 fixed on its axis, and 
CLOCKS. 
also the common wheel E of 30 teeth for 
moving a pendulum (by palettes) that vibrates 
seconds, as in a common clock. M his clock 
is wound up by a cord going over a pul- 
ley on the axis of the great wheel, like a 
common thirty-hours clock. Many of these 
admirably simple machines have been con- 
structed, which measure time exceedingly well. 
It is subject, however, to the inconvenience of 
requiring frequent winding by drawing up 
the weight, and likewise to some unceitainty 
as to the particular hour shown by the index 
A. Mr. Ferguson has proposed to remedy 
these inconveniences by the following con- 
struction : In the dial-plate ot his clock, fig. 
5, there is an opening, a b c d, below the cen- 
tre ; through which appears part of a flat 
plate : on this the 12 hours, with their di- 
visions into quarters, are engraved. This 
plate turns round in 12 hours: and the index 
A points out the true hour, &c. B is the mi- 
nute-hand, which goes round the large circle 
of 60 minutes whilst the plate ci b c d shifts its 
place one hour under the tixed index A. 1 here 
is another opening, efg h, through which the 
seconds are seen on a flat moveable ring at 
the extremity of a fleur-de-lis engraved on 
the dial-plate. A in lig. 6 is the great wheel 
of this clock, containing 120 teeth, and turn- 
ing round in 12 hours. 1 he axis of this 
wheel bears the plate of hours, which may be 
moved by a pin passing through small holes 
drilled in the plate, without affecting the 
wheel-work. 1 he great wheel A turns a pi- 
nion B of ten leaves round in an hour, and 
carries- the. minute-hand Bon its axis round 
the dial-plate in the same time. On this axis 
is a wheel C of 120 teeth, turning round a 
pinion D of 6 leaves in three minutes ; on 
the axis of which there is awheel E ot 90 teeth, 
that keeps a pendulum in motion, vibrating 
seconds by palettes, as in a common clock, 
when the pendulum-wheel has only 30 teeth, 
and goes round in a minute, in order to 
show the seconds by this clock, a thin plate 
must be divided into 3 limes 60, or 180 equal 
parts, and numbered 10, 20, 30, 40, 50,60, 
three times successively ; and lixed on the 
same axis with the wheel of 90 teeth, so as to 
turn round near the back ot the dial-plate ; 
and these divisions will show the seconds 
through the opening efg h, fig- 5. 1 his 
clock will go a week without winding, and 
always show the precise hour ; but this clock, 
as Mr. Ferguson candidly acknowledges, has 
two disadvantages of which Dr. Franklin’s 
clock is free. When the minute-hand B is 
adjusted, the hour-plate must also be set right 
by means ot a pin ; and the smallness ot the 
teeth in the pendulum wheel will cause the 
pendulum ball to describe but small arcs in 
its vibrations : and therefore the momentum of 
the ball will be less, and the times of the vibra- 
tions will be more affected by any unequal 
impulse of the pendulum wheel on the pa- 
lettes. Besides, the weight of the flat ring on 
which the seconds are engraved will load the 
pivots of the axis of the pendulum wheel 
with a great deal of friction, which ought by 
all possible means to be avoided. lo re- 
medy this inconvenience, the second-plate 
might be omitted. A clock similar to Dr- 
Franklin’s was made in Lincolnshire many 
years ago. 
Thus far refers to what is usually called 
clock-work ; but watches are so far on a dif- 
ferent construction that they are set in mo- 
tion by a spring. The manner mat a weig.it 
acts upon the cylinder, about which tne 
line or cord to which it hangs is wound, is 
ease to be understood by all ; but the action 
of the spring coiled up within toe cylindiic 
barrel, or box ot a clock or watch, is some- 
what more nice and mysterious , and the 
manner how it acts upon the fusee always 
with an equal force, by means ot the chain 
and the proper figure of the fusee tor that 
purpose, is next to be explained. 
The chain being fixed at one end of the 
fusee, and at the other to the barrel ; when- 
the machine is winding up, the fusee is turn- 
ed round, and of course the barrel ; on the 
inside of which is tixed one end of the spring,, 
the other end being tixed to an immovable 
axis in the centre. As the barrel moves 
round, it coils the spring several times about 
the axis, thereby increasing its elastic force 
to a proper degree: all 1 his while the chain' 
is drawn oil the barrel upon the fusee ; and 
then, when the instrument is wound up, the 
spring, by its elastic force endeavouring con- 
stants to unbend itself, acts upon the barrel, 
by carrying it round, by which the chain is 
drawn off from the fusee, and thus turns 
the fusee, and consequently the whole 
machinery. Now as the spring unbends it- 
self by degrees, its elastic force, by which it 
affects the fusee, will gradually decrease; 
and therefore, unless there was some mecha- 
nical contrivance in the figure of the superfi- 
cies of the fusee, to cause, that, as the spring 
grows weak, the chain shall be remove*. 1 far- 
ther from the centre of the fusee, so that 
what is lost in the spring’s elasticity is gained 
in the length of the lever: was- it not for this 
contrivance, the spring’s force would always 
be unequal upon the fusee, and thus would* 
I turn the fusee and consequently the 
i whole machinery, 1 unequally. All this is 
[ remedied bv the conical figure ot the fusee. 
| The fusee being acted upon, or put in mo— 
’ tion, by an uniform force, the great wheel, 
j which is fixed t(/it, is put into motion, and that 
drives the pinion of the centre-wheel, which' 
j centre-wheel drives the pinion of the third' 
; wheel, and this drive’s the pinion ot the con- 
j trate wheel, and this the pinion of the ba- 
lance-wheel, which plies the two palettes oiv 
the axis of the balance, and keeps- the balance 
in motion. 
The balance in a watch is instead of the 
pendulum in a clock, both serving to govern 
the motion ot the whole machinery. lo 
this balance is fixed a small steel spiral 
spring, which regulates its motions, and 
makes it equable: whence it has its name of 
regulator. 
‘When the watch is wound up, the chain, 
from the spring exerts a force upon, the fusee,, 
which gives motion to all the parts ol Ine ma- 
chine, in the following manner ;.as -wilL.be easy 
to understand, when the number of teeth iu. 
each wheel, and leaves in, the pinions which', 
they drive, are specified, and these in mo- 
dern thirty-hour watches are as follows 
Great wheel 
Teeth.. 
43 
Centre-wheel 
54 
Third wheel 
48- 
Contrate-wheel 
48 
Balance-wheel 
15 
Hence it is easy to conceive 
Leaves*. 
12 
6 - 
6 
6 
2 pallets., 
how often any. 
