'232 PHILOSOPHICAL TRANSACTIONS. [aNNO 1771. 



fluid in ad, by a quantity sufficient to saturate half the redundant 

 matter in eh. 



Carol 2. It was before said, that the fluid in the spaces ab and gh (when there 

 is any fluid in them) is repelled against the planes Aa andwh; and consequently 

 would run out through those planes, if there was any opening for it to do so. The 

 force with which the fluid presses against the planes Aa and h//, is that with 

 which the redundant fluid in ab is repelled by that in gh; that is, with which 

 half the redundant fluid in both spaces is repelled by an equal quantity of fluid. 

 Therefore the pressure against Aa and nh depends only on the quantity of 

 redundant fluid in both spaces together, and not at all on the thickness or distance 

 of those spaces, or on the proportion in which the fluid is divided between the 

 two spaces. If there is no fluid in ab and gh, a particle placed on the outside of 

 the spaces ad and eh, contiguous to the planes Aa or nh, is attracted towards 

 those planes by all the matter in ab and gh, id est, by all the redundant matter 

 in both spaces; and consequently endeavours to insinuate itself in the space ad or 

 eh; and the force with which it does so, depends only on the quantity of redundant 

 matter in both spaces together. The fluid in cd also presses against the plane 

 T>d, and the force with which it does so, is that with which the redundant fluid 

 in CD is attracted by the matter in ef. 



Carol. 3. If AD is overcharged, and eh undercharged, and the redundant 

 fluid in AD is exactly sufficient to saturate the redundant matter in eh, all the 

 redundant fluid in ad will be collected in the space cd, where it will be pressed 

 close together: the space ef will be entirely deprived of fluid, the quantity of 

 matter in it being just sufficient to saturate the redundant fluid in cd, and the 

 spaces AC and fh will be every where saturated. Moreover, if an opening is 

 made in the planes Aa or hA, the fluid within the spaces ad or eh will have no 

 tendency to run out at it, nor will the fluid on the outside have any tendency to 

 run in at: a particle of fluid too placed any where on the outside of both spaces 

 as at f, will not be at all attracted or repelled by those spaces, any more than if 

 they were both saturated ; but a particle placed any where between those spaces, 

 as at s, will be repelled from d towards e; and if a communication was made 

 between the two spaces, by the canal de, the fluid would run out of ad into eh, 

 till they were both saturated. 



Prop. 8. Prob. 4. — To determine in what manner the fluid will be disposed 

 in the space ad, supposing that all the rest of the universe is saturated with 

 immoveable fluid, and that the electric attraction and repulsion is inversely as 

 some other power of the distance than the square. I am not able, says Mr. C, 

 to answer this problem accurately, except when the repulsion is inversely as the 

 simple or some lower power of the distance ; but I think we may be certain of 

 the following circumstances. 



