66 Mr. hunter on a new Method of applying the Screw » 
therefore be lifted upwards (T^ xjr) g^th of an inch. But 
the end B of the handle ab has defcribed 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 aft at 
the handle with a force equal to 30 lbs. he may keep in equilibria 
a weight of 172800 lbs. But a fubduftion of perhaps more 
than one half of this muff be made, that he may raife the 
weight, as the friftion of the engine will be confiderable. Sup» 
pofe it to be two-thirds, the effect ftill remains equal to 57600 
lbs. or 25 tons i4cwts. and 32 lbs. 
It will eafily appear, that this method of applying the fcrew 
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 ferv© as a 
fpecimen. 
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