72 First published Paper on Electricity 



same fluid in the contrary direction ; so that as the particle at P is repelled 

 with not less force in the direction PG than in the contrary, I do not see 

 how a particle at G can help being repelled with more force in that direction 

 than the contrary, unless the air on the outside of the surface MN was 

 more overcharged than the space between P and G. 



In like manner, if any part of the surface is undercharged, the fluid 

 will have a tendency to run in at that part from the air. 



The truth of this is somewhat confirmed by the third problem ; as in 

 all the cases of that problem, the fluid was shewn to have a tendency to 

 run out of the spaces AD and EH, at any surface which was overcharged, 

 and to run in at any which was undercharged. 



119] COR. I. If any body at a distance from other over or under- 

 charged bodies be positively electrified, the fluid will gradually run out 

 of it from all parts of its surface into the adjoining air; as it is plain that 

 all parts of the surface of that body will be overcharged : and if the body 

 is negatively electrified, the fluid will gradually run into it at all parts 

 of its surface from the adjoining air. 



120] COR. II. Let the body A (Fig. 6) insulated and containing just 

 fluid enough to saturate it, be brought near the overcharged body B; 

 that part of the surface of A which is turned towards B will by Prop. II 

 be rendered undercharged, and will therefore imbibe electricity from the 

 air ; and at the opposite surface RS, the fluid will run out of the body into 

 the air. 



121] COR. III. If we now suppose that A is not insulated, but com- 

 municates with the ground, and consequently that it contained just fluid 

 enough to saturate it before the approach of B, it is plain that the surface 

 MN will be more undercharged than before; and therefore the fluid will 

 run in there with more force than before; but it can hardly have any 

 disposition to run out at the opposite surface RS ; for if the canal by which 

 A communicates with the ground is placed opposite to B, as in figure 5, 

 then the fluid will run out through that canal till it has no longer any 

 tendency to run out at RS; and by the remarks at the end of Prop. 27, it 

 seems probable, that the fluid in A will be nearly in the same quantity, 

 and disposed nearly in the same manner, into whatever part of A the canal 

 is inserted by which it communicates with the ground. 



122] COR. IV. If B is undercharged the case will be reversed; that is, 

 it will run out where it before run in, and will run in where it before 

 run out. 



As far as I can judge, these corollaries seem conformable to experi- 

 ment : thus far is certain, that bodies at a distance from other electrified 

 bodies receive electricity from the air, if negatively electrified, and part 

 with some to it if positively electrified : and a body not electrified and not 



