66 Mr. hunter on a new Method of applying the Screw. 
therefore be lifted upwards ( T ’ T x t = ) °f an inch. But 
the end b of the handle ab has deferibed above fix feet ; there- 
fore the velocity of the point g is to that of the point b as one 
to (72 x 80 = ) 5760. Therefore, if we fuppofe a man to act at 
the handle with a force equal to 30 lbs. he may keep in equilibrio 
a weight of 172800 lbs. But a fubdu&ion of perhaps more 
than one half of this muft be made, that he may raife the 
weight, as the friction of the engine will be confiderable. Sup- 
pofe it to be two-thirds, the effect {till remains equal to 57600 
lbs. or 25 tons i4cwts. and 32 lbs. 
It will eafily appear, that this method of applying the ferew 
may have a place in many other engines, particularly where 
great accuracy is required ; or we want a motion to be performed 
with great power, while at the fame time it need not have any 
large compafs. The few examples given above may ferve as a 
fpecimen. 
