[ ^22 ]' 
L'e m m a XI. 
In the line DC produced, take C F equal to C A: 
If all the matter of the plate AB is colleded in the 
'circumference, its repulfion on the column CD, in- 
finitely continued, is equal to' the repulfion of the 
fame quantity of matter colledted-in the point F, on 
the fame column. 
Imr.the repulfion of the plate on the column ira 
the diredion CD, is the fame, whether the matter 
of it be colleded in the whole circumference, or in 
the point A. Suppofe it therefore to be colleded in 
A; and let an equal quantity of matter be colleded 
in F; .take FG conftantly equal to AD,; and let 
A.D.and F-G flo.w: the fluxion of /CD is to the 
fluxion of F G, as A-D to C D ; and the repulfion 
of A on the point D, in the diredion CD, is to tlie 
repulfion of F on G, as CD to AD ; and therefore 
the fluxion of the repulfion of A on the column 
■C D, in the diredion C D, is equal to the fluxion of 
the repulliun of F on C G ; and when AD equals 
A C, the repulfion of both A and F on their re- 
fpedive columns vanilhes ; and therefore the rc- 
pulfion of A on the whole column CD equals that 
of F on CG ; and when C D and C G are both in- 
:finitqly extended, they may be looked upon as die 
fame column. 
P R O P. XVIT. 
J^et two fimilar bodies, cf difi'erent fizes, and con- 
iifting of difi'erent for'6 of matter, be both over- 
(hirged. 
