Principles of progrejjive and rotatory Motion. 573 
ftroke from Ample impact is finite, confequently its mo- 
tion muft be infinitely fmall, and therefore p mud have 
communicated all its motion to qj now in this cafe the 
velocity of Q_ ( = ^ cg + pJcd) = which quantity 
is independent of the place where the, force adls; in the 
fame manner it would appear if we had fuppofed the 
bodies elaftic. 
PROP. XII. 
Suppofing every thing given as in the loft Proportion, ex- 
cept that the direction ad does not pafs through the cen- 
ter of gravity g of the Jlriking body ; to determine the 
velocity of each body after the flroke. 
Let ad (fig. 9.) be produced to meet Fgo palling 
through g, the center of gravity of the ftriking 
body, perpendicularly in f, and fuppofe o to be the 
point of the body p which is not difturbed by the 
action of p on q_: now it appears from Cor. 6. Prop, 
xi, that if both bodies were non- elaftic, and a body 
equal to q_x — were placed at d, the velocity of that 
body, from the action of r, would be equal to the ve- 
locity of the point d of the body qj for the fame rea- 
fon, therefore, it appears, that if, inftead of fuppofing 
4 F 2 F to 
