CLOCKS. 
372 
by striking: though the name watch is com- 
monly appropriated to pocket-clocks ; and 
that of clock to larger much nes, whether 
they strike or no. 
Clocks, invention of. The invention of 
clocks with wheels is ascribed to Pucificus, 
archdeacon of Verona, who lived in the time 
of Lotbair son of Lewis the Debonnair, on the 
credit of an epitaph quoted In L "ghelb, and 
borrowed by him from Panvinius. They 
were at first called nocturnal dials, to dis- 
tinguish them from sun-dials, which showed 
the hour by the sun’s shadow. Others as- 
cribe the invention to Boethius, about A. 1). 
510. Mr. Derham makes clock-work of a 
much older standing; and ranks Archimedes’s 
sphere mentioned by Claudian, and that of 
Posidonius mentioned by Cicero, among 
the machines of this kind : not that either 
their form or use was the same with those 
of ours, but that they had their motion from 
some hidden weights or springs, with wheels, 
or pulleys, or some such clock-work principle. 
But be this as it may, it is certain the art of 
making clocks, such as are now used, was 
either lirst invented, or at least revi.ed, 
not more than 200 years ago. The clepsy- 
dra:, or water-clocks, and sun-dials, have a 
much better claim to antiquity. The French 
annals mention one ot the lor-mer kind sent by 
Aaron, kalif of Persia, to Charlemagne, about 
A. D. 807, which seemed to bear some re- 
semblance to the modern clocks. It was of 
brass, and showed the hours by 12 little balls 
of the same metal which fell at the end ot 
each hour, and in falling struck a bell and .made 
it sound. There were also figures of 1 2 cavaliers 
which at the end of each hour came forth at 
certain apertures or windows in the side of 
the clock, and shut them again, &c. The 
invention of pendulum clocks is owing to the 
happy industry «f the century before last : 
the honour of it is disputed by Huygens and 
Galileo. The former, who has written a vo- 
lume on the subject, declares it was first put 
in practice in 1657, and the description 
thereof printed in 1658. keener, dc Nova 
Temporis dimeticiidi Theoria, A. D. 1 680,- 
contends for Galileo: and relates, though at 
sejoud-haud, the whole history ot the inven- 
tion ; adding that one Tresler, clock-maker 
to the then father of the grand duke of \ us- 
cany, made the first pendulum clock at Flo- 
rence, by direction of Galileo Galilei; a pat- 
tern of which was brought into Holland, 'i lie 
Academy del Cimento says expressly, that 
the application of the pendulum to the move- 
ment of a clock was first proposed by Galileo, 
and first put in practice by his son Vincenzo 
Galilei, in 1649. Be the inventor who may, 
it is certain the invention never flourished 
till it came into Huygens’s hands, who insists, 
that if ever Galileo thought of such a thing, 
he never brought it to any degree of perfec- 
tion. The first pendulum clock made in 
England was in 1662, by Mr. Fromantil, a 
Dutchman. Before the invention of the pen- 
dulum a balance was used resembling the lly 
of a jack. 
In plate fig. I is the profile of a clock : P 
is a weight that is suspended by a rope that 
winds about the cylinder or barrel C, which 
is fixed upon the axis aw, the pivots !/b go into 
holes made in plates TS, TS, in which they 
turn freely. These plates are made of brass or 
iron, and are connected by 4 pit ars ZX ; and 
tjic whole together is called th e frame. Ihe 
weight F, if not restrained, would necessarily 
turn the barrel C with an uniform accelerated 
motion, in the same manner as it the weight 
was killing freely from a height. But the 
barrel is tarnished with a ratchet wheel Kk, 
lig. the right side of w hose teeth strikes against 
the click, which is fixed with a screw to the 
wheel D, so that the action of the weight is 
communicated to the w heel D, the teeth of 
which act upon the teeth of the small wheel d 
which turns upon tne pivots c. c. The commu- 
nication or action of one w heel with another is 
called the pitching; aWiall wheel like d is 
called a pinion, aud its teeth are leaves ol the 
pinion. Several things are requisite to form 
a good pitching, the advantages of which are 
obvious in all machinery where teeth and pi- 
nions are employed. The teeth and pinion 
leaves should be of a proper shape, and per- 
fectly equal among themselves ; the size also 
of tne pinion should be of a just proportion 
to the wheel acting into it ; and its place 
must be at a certain distance from the wheel, 
beyond or within which it will make a bad 
pitching. The wheel EE is fixed upon the 
axis ol the pinion d; and the motion com- 
municated to the wheel DD by the weight 
is transmitted to the pinion d, consequently 
to the wheel EE, as likewise to the pi- 
nion e and wheel FF, which moves the pinion 
upon the axis of which the crown or balance 
wheel G H is fixed. The pivots of the pi- 
nion / play in holes of the plates L, M, which 
are fixed horizontally to the plates TS. The 
motion begun by the weight is transported 
from the wheel G II to the palettes I k, and 
by means of the fork X U rivetted on the pa- 
lettes, communicates motion to the pendulum 
A 13, wh ch is suspended upon the hook A. 
The pendulum A 13 describes, on the point 
A, an arc of a circle alternately going and 
returning. If then the pendulum is once put 
in motion by a push of the hand, the weight 
of the pendulum at B w ill make it return upon 
itself, and if w ill continue to go alternately 
backward and lorward till the resistance of 
the air upon the pendulum, and the friction 
at tiie point of suspension at A, destroys the 
original impressed force. But at every 
vibration, of the pendulum, the teeth of the 
balance wheel, G H, act so upon the palettes 
1 K (the pivots upon the axis of these palettes 
play in two holes of the potence s t), that alter 
one tooth 14 has communicated motion to the 
palette K, that tooth escapes; then the op- 
posite tooth G acts upon the palette 1, and 
escapes in the same manner; and thus each 
tooth of the wheel escapes the palettes IK, 
after having communicated their motion to 
the palettes in such a manner that the pen- 
dulum, instead of being stopped, continues to 
move. The wheel E E revolves in an hour ; 
the pivot c of this wheel passes through the 
plate, and is continued to r ; upon the pivot 
is a wheel N N with a long socket fastened 
in the centre : upon the extremity of this 
socket r, the minute-hand is fixed. The 
wheel NN acts upon the wheel O; the 
pinion of which p acts upon the wheel q q, 
fixed upon a socket, which turns along w ith 
the wheel N, This wheel q q makes its re- 
volution in 1 2 hours, upon the socket of which 
the hour-hand is fixed. Thus it is plain, 
1. That the weight P turns all the wheels, 
and at the same time continues the motion of 
the pendulum : 2. That the quickness of the 
motion of the wheels is determined by bloat of 
the pendulum. 3. That the wheels point 
out the parts of time divided by the uniform 
motion of the pendulum. W hen the cord 
upon which the weight is suspended is en- 
tirely run down from oil the barrel, it is 
wound up again by a key, which goes on 
the square euti of the arbor at Q, by turning 
it in a contrary direction to that in which the 
weight descends. For this purpose, the in- 
clined side of the teeth ot the wheel K, fig. 2, 
removes the click G, so that the ratchet- 
wheel R turns while the wheel D is at rest ; 
but as soon as the cord is wound up, the 
click falls in betw een the teeth of the wheel 
D, and the right side of the teeth again acts 
upon the end of the click, which obliges the 
wheel 1) to turn along with the barrel; and 
the spring A keeps the click between the teeth 
of the ratchet-wheel R. 
To explain how time is measured by the 
motion ol the pendulum ; and how the wheel 
E, upon the axis of which the minute-hand is 
fixed, makes but one precise revolution in an 
hour ; we must observe, that the vibrations of 
a pendulum are performed in a shorter or 
longer time ini proportion to the length ot the 
pendulum itself. A pendulum of 3 feet 8^ 
French lines in length, makes 3600 vibrations 
in an hour : i. e. each vibration is peformed 
in a second of time, and for that reason it is 
called a second pendulum, but a pendulum 
oi 9 inches 3-y French lines makes 7200 vi- 
brations in an hour, or two vibrations in a 
second of time, and is c alled a ha f second 
pendulum. Hence, in constructing a wheel 
whose revolution must be performed in a 
given time, the time of the vibrations ot the 
pendulum which regulates its motion, must 
be considered. Supposing, then, that the 
pendulum A 13 makes 7200 vibrations in an 
hour, let us consider how the w heel E shall 
take up an hour in making one revolution. 
This entirely depends on the number of teeth 
in the w heels and pinions. If the balance 
wheel consists of 30 teeth, it will turn once in 
the time that the pendulum makes 60 vibra- 
tions : for at every turn of the wheel, the 
same tooth acts once on the palette 1, and 
once on the palette K, which occasions two 
separate vibrations in the pendulum ; and the 
wheel having 30 teeth, it occasions twice 30, 
or 60, vibrations. Consequently, this wheel 
must perform 120 revolutions in an hour; 
because 60 vibrations, which it occasions at 
every revolution, are contained 120 times in 
7200, the number of vibrations performed by 
the pendulum in an hour. To determine the 
number of teeth for the wheels E E, and their 
pinions e,f, it must be remarked, that one re- 
volution otthe wheel E must turn the pinion 
c as many times, as the number of teeth 
in the pinion is contained in the number 
of teeth in the wheel. Thus, if the wheel 
E contains 72 teeth, and the pinion e, 6, the 
pinion will make 12 revolutions in the time 
that the wheel makes 1 ; for each tooth of the 
wheel drives forward the tooth of the pi- 
nion ; and when the six teeth of the pinion 
are moved, a complete revolution is per- 
formed ; but the wheel FI has by that time 
only advanced 6 teeth, and has still 66 to ad- 
vance before its revolution is completed, 
which will occasion 11 more revolutions of the 
pinion. For the same reason, the w heel F hav- 
ing 60 teeth, and the pinion/ 6, the pinion 
will make 10 revolutions while the wheel per- 
forms one. Now, the wheel F, being turned 
