320 H OEO 
neceflarily attend its winding and unwinding. It fliould 
be of uniform breadth throughout; and the rims fhould 
be rounded, that they may not fcratch the bottom or top 
of the barrel, and that the friction again!! thefe two parts 
may be as equal and as little as poffible. Broad or high 
fprings, -within certain limits, are to be preferred, as they 
work more equally in the fame plane, confequently have 
lefs. friction againft the top and bottom of the barrel., 
The two ends of the fpring mult be untempered, in or¬ 
der to facilitate the making the fquare holes by which it 
is to be hooked to the barrel and barrel-arbor, and to pre¬ 
sent it from breaking at thofe places. The lituation of 
the hook which holds the fpring to the arbor is not a 
matter of indifference. It is frequently left fo high, that 
it bears up the fpring immediately upon it, by which 
means thofe parts, during the contraction (or winding) 
of the fpring, become fo violently and unproportionably 
heated by the configuration, that it breaks at the molt 
agitated part. Workmen, in the habit of putting main 
fprings into barrels, frequently fee them break in the act 
of railing about two or three turns from the arbor ; which 
mult proceed from one of the foregoing reafons, either 
too fmall an arbor, or too long a hook. Mr. Parr, the 
author of an (unfinilhed) Treatife on Pocket Watches, 
2804, obferves as follows: “I called at the Ihop of a 
finiflier in the year 1796, who -was finilhing a high-priced 
horizontal watch. The main-fpring he happened to 
break juft on my entering his Ihop, and, according to 
cultom, proceeded to the fpring-maker for a new one. 
During bis abfence, I examined' the barrel-arbor, and 
found the hook about one thicknefs of the fpring too 
high, and informed him of it on his return; but he de¬ 
termined to try a fecond, which lhared exactly the fame 
fate ; it broke three turns from the eye, or hook-hole. 
He proceeded again to the fpring-maker for a third, 
which broke only two turns from the eye. By this 
means, together with the lofs to the fpring-maker, he em¬ 
ployed three hours of his time, which induced me again 
to requeft him to lower his hook. This, after much per- 
fuafion he did, with feeming reluctance, obferving at the 
lame time, the Heel of which the fprings were made mull 
be bad. However, having examined the lalt broken 
fpring, and finding a clear grain and full length, I re¬ 
queued his permifiion to re-make it, which I accomplish¬ 
ed, by drawing the fpring from the curl, lowering the 
temper of it at the arbor end, making a new hook-hole, 
and turning it again into the barrel, which, to his fur- 
prife, made an equal adjuftment. The fame workman 
has iince informed me, that, by obferving my rule, he 
has not had two broken fprings in a year; and frankly 
declares, that, before he knew that rule, he had frequent¬ 
ly two or three in one day. Pie faid alfo, that, from the 
fullnefs of the fpring in the barrel, which mult unavoid- 
• ably reduce the arbor, to give Sufficient turns, if the fpring* 
is not Ihortened, he very Seldom procured a paffable ad¬ 
juftment. 
We have now to Speak of the fufee, which is an aflift- 
ant to the moving power, tending to make aCtion of the 
main-fpring upon the wheel-work equal in all its wind¬ 
ings. The fufee is in the form of a truncated cone, and 
carries the firft wheel which communicates the power of 
fpring to the train of wheels : this power is communi¬ 
cated" to the fufee by means of the chain , which winds 
and unwinds in a Spiral groove round the circumference 
of the fufee. When the watch is wound up, the chain is 
all upon the fufee except that fmall part which connects 
the fufee to the fpring-barrel. The watch being now in 
motion, the chain gradually difengages itfelf from the 
fufee, by the impulfe of the fpring turning the barrel ; 
and, when the chain is all round the barrel, the watch is 
down. 
Now the effect, or aftion, of the fpring, is continually 
diminilhing from firft to lalt; and, unlefis that inequality 
were rectified, it would draw the chain with more force, 
and wind a greater quantity upon the box, at the firft 
LOGY. 
going than afterwards ; hence the machine could never 
keep equal time, but would go flower and flower as the 
chain advanced upon the barrel. To correft this in¬ 
equality in the moving power, nothing could be-more 
happily contrived than to have the fpring applied to the 
arms of levers which are continually longer as the force 
of the fpring is weaker:, for this is the effedt of the fufee; 
and it is for this reafon that it is made of a conical form. 
Its axis, which is immoveable, is the feries of the centres 
of all the unequal circumferences which compole the fur- 
face of the fufee. According as the part of the chain 
which is untwifting is applied to a larger circumference, 
it is at a greater diftance from the fixed point in the 
axis correfponding thereto ; and of coaifequence the power 
which draws by this chain, viz. the fpring, atfs with more 
advantage. This fpring begins to draw from the vertex 
of the cone, the molt dil'advantageous part, becaule its 
own force is then the greateft. The chain is connected 
to the upper part of the lpring-barrel by a hook of the 
form llioAvn at fig. 4.9, and to the lower part of the fufee 
by one of the form at fig. 50. The axis of the fufee ter¬ 
minates in a fquare arbor; to this the key is applied to 
wind up the watch. The wheel at the bottom of the fu¬ 
fee is not acted upon by the turning of the fufee in the 
winding-up of the watch, though when the watch is go¬ 
ing it makes as many revolutions as there are turns of 
chain on the fufee, and always in the fame direction. 
The fufee is hollowed out underneath to admit of a 
ratchet-wheel and click to keep the wheel Iteady while 
the fufee is turned in a retrograde direction for winding 
up the watch; but, when the lpring is wound up, the 
wheel follows the motion of the fufee ; and, working in 
the firft pinion of the train, communicates the power of 
the fpring to the reft of the machine. 
III. Of the WHEEL-WORK. 
The wheel-work communicates, through a train of 
wheels and pinions, the aCtion of the moving power to 
the regulator. The fwiftnefs of the wheels increafes in 
proportion to their diftance (being intercepted by other 
wheels) from the moving power ; but they decreafe in 
force or ftrength in proportion to their velocity. The 
Itrength of the laft or Icapement wheel Ihould be fuffi- 
cient to repair the lofs of motion which the regulator is 
fubjeCt to from the reliftance of the air and from friftion; 
and confequently it muft be proportionate to the number 
of revolutions of the laft wheel, and increafe or diminiih 
in the ratio of its velocity. Suppofingthe required ftrength 
of the laft wheel =1, and the number of its revolutions 
during one revolution of the firft wheel — 4800, then the 
moving power muft be 4800 times greater than that of 
the laft wheel, according to the firft principles of mecha¬ 
nics, allowance being made for the influence of friction. 
Velocity increafes by combining two wheels of differ¬ 
ent diameters in fuch a manner that the larger wheel may 
drive the fmaller, which is called a pinion. The pinion 
will make more revolutions than the wheel in proportion 
as its diameter is lefs than that of the wheel; fo that the 
velocity of the laft mover may be increased at pleafnre, 
by combining leveral wheels and pinions, fo that the firlt 
wheel fliall drive a pinion carrying concentrically a ie- 
cond wheel, and this fecond driving a fecond pinion car¬ 
rying a third wheel, and drawing another pinion carrying 
a fourth wheel, &c. &c. This aflemblage of wheels and 
pinions is called the wheel-work, Or train ; and by this 
means the moving power may be made to aft for a confi- 
derable time, and even for a given time, upon the regu¬ 
lator, till it may be neceffary to renew it, or, in other 
words, to wind up the machine. The wheel-work alfo 
impels the indexes, or hands, which point out the time 
.elapfed. 
The number of teeth in two wheels which conr.eft and 
work together fliould be in proportion to their diameters.— 
Example. Suppofe the diameter of a wheel =: 30, and of 
a fmaller wheel, or pinion, = 3; the wheel having 120 
tec, h-, 
