VOL. LXI.] PHILOSOPHICAL TRANSACTIONS. 33/ 



Mr. C. sees no reason however to think that that will prevent the body 

 D from being undercharged; but he cannot say exactly what effect it will 

 have, except when abc is spherical, and the repulsion is inversely as the 

 square of the distance; in this case it appears, by prob. 1, that the fluid 

 in the part db of the canal will be repelled from c, with just as much force 

 as in the last proposition; but the fluid in the jiart bg will not be repelled 

 at all: consequently d will be undercharged, but not so much as in the last pro- 

 position. 7!i!rj vr;i; ii 



Carol. If ABC is now supposed to be undercharged, it is certain that d will be 

 overcharged, provided the matter near abc on the outside is saturated with im- 

 moveable fluid; and there is great reason to think that it will be so, though the 

 fluid in that matter is moveable. 



Ptop. 16. Let aefb, fig. 9, be a long cylindric body, and d an undercharged 

 body ; and let the quantity of fluid in aefb be such, that the part near ep shall 

 be saturated. It appears, from what has been said before, that the part near 

 AB will be overcharged; and moreover there will be a certain space, as xabs, 

 adjoining to the plane ab, in which the fluid will be pressed close together; and 

 the fluid in that space will press against the plane ab, and will endeavour to es- 

 cape from it; and, by prop. 2, the two bodies will attract each other: then the 

 force with which the fluid presses against the plane ab, is very nearly the same 

 with which the two bodies attract each other in the direction ea; provided that 

 no part of aefb is undercharged. 



Suppose so much of the fluid in each part of the cylinder, as is sufficient to 

 saturate the matter in that part, to become solid; the remainder, or the redun- 

 dant fluid remaining fluid as before. In this case the pressure against the plane 

 ab must be exactly equal to that with which the two bodies attract each other, 

 in the direction ea: for the force with which D attracts that part of the fluid 

 which we supposed to become solid, is exactly equal to that with which it repels 

 the matter in the cylinder ; and the redundant fluid in eg^f is at liberty to move, 

 if it had any tendency to do so, without moving the cylinder; so that the only 

 thing which has any tendency to impel the cylinder in the direction ea, is the 

 pressure of the redundant fluid in Aabs against ab ; and as the part near ef is sa- 

 turated, there is no redundant fluid to press against the plane ef, and thus to 

 counteract the pressure against ab. Suppose now all the electric fluid in the 

 cylinder to become fluid ; the force with which the two bodies attract each other, 

 will remain exactly the same; and the only alteration in the pressure against ab, 

 will be, that that part of the fluid in ag^b, which we at first supposed solid and 

 unable to press against the plane, will now be at liberty to press against it; but 

 as the density of the fluid, when its particles are pressed close together, may be 

 supposed many times greater than when it is no denser than sufliicient to saturate 



