VOL. LXI.3 PHILOSOPHICAL TRANSACTIONS. 235 



be SO also. For as the fluid in the canal is repelled by the redundant fluid in d, 

 it is plain, that unless a was overcharged, so as to balance that repulsion, the 

 fluid would run out of d into a. In like manner, if one is undercharged, the 

 other must be so too. 



Prop. 11. Let the body a (fig. 6) be either saturated or over or undercharged; 

 and let the fluid within it be in equilibrio. Let now the body b, placed near it, 

 be rendered overcharged, the fluid within it being supposed immoveable, and 

 disposed in such manner, that no part of it shall be undercharged; the fluid in 

 A will no longer be in equilibrio, but will be repelled from b; therefore the fluid 

 will flow from those parts of a which are nearest to b, to those which are more 

 distant from it; and consequently the part adjacent to mn (that part of the sur- 

 face of A which is turned towards b) -vill be made to contain less electric fluid 

 than it did before, and that adjacent to the opposite surface rs will contain more 

 than before. 



It must be observed, that when a sufiicient quantity of fluid has flowed from 

 MN towards rs, the repulsion which the fluid in the part adjacent to mn exerts 

 on the rest of the fluid in a, will be so much weakened, and the repulsion of 

 that in the part near rs will be so much increased, as to compensate the repul- 

 sion of B, which will prevent any more fluid flowing from mn to rs. The reason 

 why he supposes the fluid in b to be immoveable, is, that otherwise a question 

 might arise, whether the attraction or repulsion of the body a, might not cause 

 such an alteration in the disposition of the fluid in b, as to cause some parts of 

 it to be undercharged; which might make it doubtful, whether b did on the 

 whole repel the fluid in a. It is evident however, that this proposition would 

 hold good, though some parts of b were undercharged, provided it did on the 

 whole repel the fluid in a. 



Corol. If B had been made undercharged, instead of overcharged, it is plain 

 that some fluid would have flowed from the farther part rs to the nearer part 

 MN, instead of from mn to rs. 



Prop. 12. Let us now suppose that the body a communicates by the canal 

 EF, with another body d, placed on the contrary side of it from b, as in fig. 5 ; 

 and let these two bodies be either saturated, or over or undercharged ; and let 

 the fluid within them be in equilibrio. Let now the body b be overcharged : it 

 is plain that some fluid will be driven from the nearer part mn to the farther part 

 RS, as in the former proposition ; and also some fluid will be driven from rs, 

 through the canal, to the body d ; so that the quantity of fluid in d will thus be 

 increased, and the quantity in a, taking the whole body together, will be dimi- 

 nished, the quantity in the part near mn will also be diminished: but whether the 

 quantity in the part near rs will be diminished or not, does not appear for cer- 

 tain ; but Mr. C. imagines it would be not much altered. , ., . 



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