jo First published Paper on Electricity 



until, by the action of the electrified body on it, it has either acquired 

 some additional fluid from the air, or had some driven out of it, or till 

 some fluid is driven from one part of the body to the other. 



113] CASE VIII. Let us now suppose that the two bodies A and B 

 are both positively electrified in the same degree. It is plain, that were 

 it not for the action of one body on the other, they would both be over- 

 charged, and would repel each other. But it may perhaps be said, that 

 one of them as A may, by the action of the other on it, be either rendered 

 undercharged on the whole, or at least may be rendered undercharged in 

 that part nearest to B ; and that the attraction of this undercharged part 

 on a particle of the fluid in B, may be greater than the repulsion of the 

 more distant overcharged part; so that on the whole the body A may 

 attract a particle of fluid in B. If so, it must be affirmed that the body B 

 repels the fluid in A ; for otherwise, that part of A which is nearest to B 

 could not be rendered undercharged. Therefore, to obviate this objection, 

 let the bodies by joined by the straight canal DC of incompressible fluid 

 (Fig. 19) . The body B will repel the fluid in all parts of this canal ; for as 

 A is supposed to attract the fluid in B, B will not only be more overcharged 

 than it would otherwise be, but it will also be more overcharged in that 

 part nearest to A than in the opposite part. Moreover, as the near under- 

 charged part of A is supposed to attract a particle of fluid in B with more 

 force than the more distant overcharged part repels it; it must, a fortiori, 

 attract a particle in the canal with more force than the other repels it; 

 therefore the body A must attract the fluid in the canal ; and consequently 

 some fluid must flow from B to A , which is impossible ; for as A and B are 

 both electrified in the same degree, they contain the same quantity of fluid 

 as if they both communicated with a third body at an infinite distance, by 

 canals of incompressible fluid ; and therefore, by the corollary to Prop. 24, 

 if a communication is made between them by a canal of incompressible 

 fluid, the fluid would have no disposition to flow from one to the other. 



114] CASE IX. But if one of the bodies as A is positively electrified 

 in a less degree than B, then it is possible for the bodies to attract each 

 other ; for in this case the force with which B repels the fluid in A may be 

 so great, as to make the body A either intirely undercharged, or at least 

 to make the nearest part of it so much undercharged, that A shall on the 

 whole attract a particle of fluid in B. 



It may be worth remarking with regard to this case, that when two 

 bodies, both electrified positively but unequally, attract each other, you 

 may by removing them to a greater distance from each other, cause them 

 to repel ; for as the stronger electrified body repels the fluid in the weaker 

 with less force when removed to a greater distance, it will not be able to 

 drive so much fluid out of it, or from the nearer to the further part, as 

 when placed at a less distance. 



