SO'B HOROLOGY. 
a horizontal trough, fupported like a balance by a fulcrum 
af K, in fuch a manner, that either end of the balance 
may be elevated accordingly as the long veifels AB and 
CD require to be alternately tilled ; near the top of each 
of thele veffels is ini'erted a long fyphon or tantaius, L and 
m, the lower legs of which reach down to two ftnall cy¬ 
lindrical vefiels, n and o, which are poiled by another ba¬ 
lance at the fulcrum p-, thele cylindrical veffels have, in 
like manner, each a fmall fyphon, q and r; laftly, a filken 
thread'tied to the upper end of the cylinder, n, is carried 
up round a fmall pulley fall to the frame at s, and is 
fattened to the end of the trough under it, and a fimilar 
thread is fattened in like manner to the cylinder o, and end 
of the trough under the fmall pulley t. Now it is eafy to 
conceive, that when the velfel, AB, is filled to nearly the 
head of the tantaius /, the bore of which is larger than of 
the feeding fyphon I, the water will be difcharged into the 
cylindrical vale n, which confequently will preponderate, 
and by means of the filken chord elevate the end of the 
trough higher than the horizontal line, and make its op- 
pofite end under the fmall pulley, t, to be depreffed, which 
will therefore conduft the water into the other long velfel 
CD; during this action the counterpoife, F, riles, and its 
pulley, f, produces no efi’eft on the ratchet by reafon of 
the click, h, Hiding over the Hoping fides of its teeth ; but 
the counterpoife, G, falls, and the click of its pulley (not 
feen) pulhes the fecond ratchet forwards in the direction 
of the figures of the face I. II. III. etc. 
When CD is nearly full, the long fyphon, m, begins to 
difebarge its water; makes the cylindrical vale, o, prepon¬ 
derate, and again elevates-by means of its filken firing the 
end of the trough under the fmall pulley t, and deprelfes 
the oppofite end to fill the velfel, A B, again, during which 
time the' click, h, of the pulley, f, afts with its ratchet; 
and thus the alternate increafe and decreafe of the water 
in the two veffels are continued without interruption, fo 
long as the feeding fyphon continues to l'upply a lulficient 
quantity of pure water. We think, however, that the 
mechanilin is nearly as complex as that of a clock itfelf; 
and therefore we lhall dwell no longer on this 1'abject, 
more curious certainly than ufeful; but proceed to the 
jaft and molt important divifion of our iubjeft. 
III. Of MACHINES -with TOOTHED WHEELS. 
tinder this defignation we include every kind of tinre- 
■meafurer, compoi'ed of a pendulum or balance, a fpring 
or weight, and a train of wheels; as clocks, watches, and 
time-pieces for various purpol’es. 
GENERAL PRINCIPLES or TIME-MEASURERS. 
From motion proceeds the natural meal'urement of time. 
A body or fubfiance put in motion will pals over a cer¬ 
tain {pace in a certain time. Such body, if lufpended by 
a thread and then put in motion, will ofcillate round the 
point of fufpenfion. Thefe ofcillations, or vibrations , will 
be performed in equal times, and may therefore ferve to 
meafure time. This vibrating body is called a Pendu¬ 
lum. According to the laws of motion, a pendulum 
thus let in motion Would vibrate continually: but the 
refiftance of the air, and the fiilfnefs of the wire, or, what 
amounts to the lame thing, the friction of the wire at the 
centre of ofcillation, will lelfen by degrees the velocity of 
the motion, and at length Hop it entirely. To produce 
therefore lomething like a perpetual motion, we mult em¬ 
ploy lpme exterior agent to counteraft thefe obstacles. 
As long as this agent afts, the pendulum will vibrate ; 
and, by knowing the number of vibrations and the time 
of each, we lhall know the portion of time which elapfes 
duri.ng the obferyation. But, to avoid the trouble of 
eounting-thefe vibrations, we difpolethe mechanifm which 
works upon the pendulum in fuch a manner that the 
number of vibrations, or the time thereby meafured, may 
be fhown by an index, or fiyle, which in a clock is com¬ 
monly caiied the hand. 
Pendulums will not meafure time correclly unlefs they 
vibrate round a fixed point; they cannot therefore be 
nfed for portable time-pieces’, fuch as pocket-watches, See, 
In thefe machines we l'upply the place of the pendulum 
by a body vvhofe vibrations are not materially affefted 
by the motion of the whole machine. A circular body, 
turning upon its own axis, and having the centre of mo¬ 
tion and the centre of gravity in the lame point, is cal¬ 
culated to preferve its motion in every polition. A con¬ 
trivance of this kind is called a balance ; and to perpetuate 
its motion, we apply, as to the pendulum, an external 
force to repair the lol's of motion. This power afts alter¬ 
nately in contrary directions, in order that the balance, 
having palled through a certain fpace, may return with 
equal velocity. 
The motive power in time-meafurers with a pendulum is 
ufually produced by the application of a weight. In time¬ 
pieces to be carried about, it is impofiible to employ a 
weight, becaufe a weight, a cling always in a line perpen¬ 
dicular to the centre of the earth, would have more or 
lefs efieft, or none at all, according to the actual pofitiou 
of the machine, as is fufficiently. evident. Infiead of a 
weight, therefore, we employ an elaltic body, which, be¬ 
ing bent or coiled up, produces a conliderable effeCt. 
This is called a fpring ; and, as it afts by its elafticity, 
and not by its weight, we may readily conceive that the 
polition of the time-piece will not affect it. 
The motive power communicates its efieft through a 
train of wheels and pinions, which, by moving each other, 
act upon that part bf the time-piece called the feapement.. 
This lafi gives the necellkry impulfes to the vibrating 
body; befides this, it numbers the vibration's; and by 
this means the wheel-work which carries the hands Ihows 
the time. 
The wheels and pinions act by means of teeth cut in 
their circumference : but the teeth of pinions are called 
leaves. Wheels and pinions turn upon pivots, which are 
nothing but the extremities of their axes reduced to a 
fmaller diameter. 
The fpring afts in a cylinder which turns round an 
axis : this cylinder is caiied the barrel, and the axis the 
barrel-arbor. The fpring is in the form of a fpiral line ; 
when it is to aft in the barrel, its two extremities are 
faftened, one to the arbor, the other to the circumference 
of the barrel. In fixing the barrel, we bend the fpring 
by turning the arbor in a proper direction, as the fpring 
then coils round the arbor: but in fixing the arbor, we 
bend the fpring by turning the barrel. The arbor is 
made Heady by means of a ratchet, or wheel with inclined 
teeth, which is ached upon by a click, or flop, and fome- 
times bv an endlcfs ferezo. 
To the balance is applied a fmall fpring to regulate its 
vibrations. This is fometimes called, from its form, the 
fpiral fpring ; and fometimes the pendulum-fpring, but with 
more propriety the balance-fpring. The ftronger or thicker 
this fpring, the quicker will be the vibrations of the ba¬ 
lance. In common watches, a mechanifm is applied to 
this fpring, which, by lengthening or Ihortening the outer 
coil of the fpiral, lefiens or increales the quicknefs of the 
vibrations: this is called the curb and flide ; it is in raft 
the regulator. 
The wheels commonly turn between two pieces of cop¬ 
per or brafs called plates, connected by pillars lecured with, 
pins. The pivot-holes are either limply drilled in the brafs. 
plates, or elfe, the hole being made larger, is filled with 
a collet of fome harder fubfiance in which the pivot is to 
aft, as fteel, a ruby, &c. The piece above the upper 
plate, in which the upper pivot of the balance moves, is 
called the cock. ■ 
It is evident, then, that the principal and efiential 
parts of a clock or watch are thefe four: i. The pendu¬ 
lum, or the balance, as the cafe may be. 2. The moving, 
power, whether weight or fpring. 3. The maintaining 
power, or wheel-work. 4. The Icapcment. 
I.. Gf 
