Principles of progreffive and rotatory Motion . 559 
PROP. VIII. 
1 
Let a motion be communicated to the lever obliquely , to de- 
termine the point about which the bodies begin to revolve. 
LetFD (fig. 4.) reprefent the force communicating the 
motion at the point d, which refolve into two others fh, 
hd, the former fh parallel to the lever, and the latter hd 
perpendicular to it. Let c be the point about which the 
bodies would have begun to revolve, had the force hd 
only adted, and which may be found by Prop. I : and 
fuppofe in this cafe mgn to have been the next poii- 
tion of the lever after the commencement of the mo- 
tion, or that the bodies a, b, and center of gravity g, 
had been carried to m , g and n refpedfively. But as the 
force fh a efts at the point d at the fame time in the direc- 
tion of the rod, if we take Gq : g g as fh : hd, then whilffi 
the center of gravity would have moved from g to g in 
confequence of the force HD,it will by means of the force 
fh be carried in the direction of the lever from g to q , 
and alfo every other point of the lever will be carried in 
the fame direction with the fame velocity ; take there- 
fore a p and Br each equal to Gq, and complete the pa- 
rallelograms a a, gw and b b, and the bodies a, b, and 
center of gravity g will, at the end of that time, be 
found 
