Various cases of electric distribution 69 



It must be observed, that if the repulsion of B on a particle at E, 

 (Fig. 19) the farthest part of A, is very small in 

 respect of its repulsion on an equal particle placed 

 at D, the nearest part of A, the two bodies will 

 attract with very nearly the same force, whether 

 A is insulated or not ; but if the repulsion of B, on 

 a particle at E, is very near as great as on one at D, Fig Ig 



they will attract with very little force if A is 

 insulated. For instance, let a small overcharged ball be brought near one 

 end of a long conductor not electrified; they will attract with very near 

 the same force, whether the conductor be insulated or not; but if the 

 conductor be overcharged, and brought near a small unelectrified ball, 

 they will not attract with near so much force, if the ball is insulated, as 

 if it is not. 



109] CASE III. If we now suppose that A is negatively electrified, 

 and not insulated, it is plain that they will attract with more force than 

 in the last case ; as A will be still more undercharged in this case, than in 

 the last. 



no] N.B. In these three cases, we have not as yet taken notice of 

 the effect which the body A will have in altering the quantity and dis- 

 position of the fluid in B ; but in reality this will make the bodies attract 

 each other with more force than they would otherwise do ; for in each of 

 these cases the body A attracts the fluid in B; which will cause some 

 fluid to flow from the farther parts of B to the nearer, and will also cause 

 some fluid to flow into it, if it is not insulated, and will consequently 

 cause B to act upon A with more force than it would otherwise do. 



in] CASES IV, V, VI. Let us now suppose that B is negatively 

 electrified ; and let A be insulated, and contain just fluid enough to saturate 

 it ; they will attract each other; for B will be undercharged ; it will therefore 

 attract the fluid in A , and will cause some fluid to flow from the farthest 

 part of A, where it is attracted with less force, to the nearer part, where 

 it is attracted with more force ; so that B will attract the fluid in A with 

 more force than it repels the matter. 



If A is now supposed to be not insulated and not electrified, B being 

 still negatively electrified, it is plain that they will attract with more 

 force than in the last case: and if A is positively electrified, they will 

 attract with still more force. 



In these three last cases also, the effect which A has in altering the 

 quantity and disposition of the fluid in B, tends to increase the force with 

 which the two bodies attract. 



112] CASE VII. It is plain that a non-conducting body saturated with 

 fluid, is not at all attracted or repelled by an over or undercharged body, 



