Mr. Vince's Observations , &c. 
38 
what has been proved, the effects of the two parts ZX, 
Z Y to turn the lever about A is the same as if the weight 
of each part were collected into B and C respectively, which 
weights are manifestly as ZX, ZY, and which therefore 
conceive to be placed at B and C. Now AB = AX — XB 
-|XY — } X Z = { Y Z ; and AC = AY — YC = 
IXY-|ZY = {XZ; consequently AB : AC::{YZ: 
IXZ: : Y Z : X Z : : the weight at C : the weight at B. 
The property of the straight lever being thus established, 
every thing relative to the bent lever immediately follows. 
