FUS 
than the ruler as is equal to the diameter @ «+ of the circle 
and make one end of it faft to the end, by of the 
i d in the other focus 73 
be equal t 
hyperbolic curve. 
on paper, for any particular main-fpring, it may be trans- 
ferred to card-paper, or inect-brals 5 as a attern or gauge 
to be applicd to the fufee-engine, as will be hereafter de- 
bed 
hyperbolic curve. 
ine have been devifed by different ingenious workmen, but 
it would be dificult to trace each modification to its re{pec- 
nd 
tive inventor, nor 
ie] 
Ps) 
eu 
° 
o 
° 
ufeful in pratice, from 
obvious to the mechanitt, 
which, 
reprefented b : 
is tha 
cutting engine we 
and we have reafon to believe that the fufee-engine before us 
was contrived by the i i i 
folid block of hard wood, that may hi 
to fup m fup- 
frame ver 
that paffes through circular holes in the puppets E and F, 
be turned by; the cylindrical piece 
of fteel, K, paffes through the puppet G, and is fixed at 
le b : 
{crew at its lower end, as feen in fiz. 2, and the oblong hol¢ 
er end receives the projecting pin of lever M 
fo that when this lever revolves with the mandril, the dog 
and fufee are carried round at the fame time. On the pro- 
G, which have -each 
fequently may be fixed over any part o rifm 
be oppofite the fufee O, or any part of it; along this third 
prifm, S, flides the upright bearer T, that may alfo be 
fixed at any diftance from the end of S by another thumb- 
ars under it; the bearer, T, therefore 
fufee, 
: ? 
otherwife the groove cut by the faid point would form a 
circle only on the furface of the fufee ; to render.the groove 
{piral; therefore, is the bufinefs of the remaining portion 
of the apparatus. 
a long metallic frame with its fides made 
fo as to flide without fhake within the 
» which are 
to] 
fo} 
er 
r n at d, centre of motion; the extreme 
crofs-pieces or end pieces of the frame have each a circular 
perforation quite through, large enough to admit each a 
{crew through them, oF which the milled nuts are vifible 
near W obvious, therefore, that 
may be, graduated ; for when 
centre from its parallel pofition, as m the figure, the thumb- 
{crews will a& on its extreme ends, and fet it faft. 
Laftly a weight, V, is fufpended by a cord, going round a 
fixed fri€tion-wheel on the cheek aa of puppet E, and made 
, at the end near R, fo as to pull 
; towards the 
the ftraight edge of the inclined bar, in which fituation the 
prifm in queftion will remain at reft while the frame is at 
reft; but when the frame is made to n pinion 
of the winch, the weight, V, preferves the contact of the 
nclined bar, and 
elaftic bar, ff, with: 
{cending, pulls.after it the prifm Q, with its cutting-toal, 
3U2 the 
