ELECTRICITY. 



'. o pressed close together; the quantity of rcdun- 

 . (Ln fluid I ...If the whole nMumlont fluid 



HI both sport -)>.u< -i D the fluid will be praav 



utitv of fluid in it luing such, 

 ;il I'M IK' to saturate thr mat- 

 ter in 1 lie space El" will be entirely deprived cif 

 fluid ; .'.ter in it being MR-)), that tin; 

 ill l>e iliat sufficient to saturate the mat- 

 ter iii it : ivnseo.uintly the redundant fluid in CD will 

 \tc just MilticiiMil to saturate tile redundant matter in 

 ;,ira AH and Ull together contain the whole rc- 

 diiiul.int Ihiiil or matter in Ixith space-, the spaces HI) 

 HT contain tlieir natural quantity of 

 .mil therefore, a-. IK and I-'G each contain their 

 :! quantity of fluid, the spaces CD and EF to- 

 t-iin tlieir natural quantity of fluid. And, 

 llll, the space* HC and I'G will be saturated in all parts, 

 l-i. it the lluiil is disposed in this manner, no 

 particle of k Can have any tendency to move; lor a 

 !in where in the sp:-o - iH and I-'G. is 

 Attracted with just a- much tone l>\ 1!I-', .is it is repi-.l- 

 l I) : and it i- ivpi lied or attracted with just as 

 miicli force In AH. as it is in a contrary direction by 

 (11, and consequently has no tendency to move. 

 ;'icli- placed anj where in tlie space CD, or in the 

 Al'i.i'.i'i ('II, if they are overcharged, is indeed 

 .led with more force towards the planes Drf, Aa, and 

 hail it is in the contrary direction ; but as the fluid 

 m tlu is already as much compressed as pos- 

 sible, the particle will have no tendency to move. 

 _'d, It socnis impossible that the fluid should be at 

 it' it is dis(K>scd in any other manner ; but as this 

 .if the demonstration is exactly similar to the lat- 

 ter part of that of problem first, it is omitted. 



,il. 1. If the two spaces AD and I.H are both 

 >,], the redundant fluid in CD is half the dif- 

 the redundant fluid in these spaces: for half 

 .ice of the redundant fluid in those spaces, 

 . Uled to the quantity in AH, which is half the sum, u 

 equal to the whole quantity in AD. For a like reason, 

 it' AD and EH are both undercharged, the redundant 

 natter in El-' is half tXe difference of the redundant 

 matter in those spaces ; and if AD is overcharged and 

 EH undercharged, the redundant fluid in (!) rvcivd.-i 

 half the redundant fluid in AD, by a quantity sufficient 

 to saturate half the redundant matter in Ell. 



C'ortV. ~. It was before said, that the fluid in the 

 ^paces AH and GH (when there is any fluid in them) 

 is repelled against the planes An and H/i ; and con- 

 .-vcjiicntly would run out through those planes, if there 

 any opening for it to do so. The force with 

 which the fluid presses against the planes An and H/(, 

 ii that with which the redundant fluid in AB is repelled 

 l.y that in GI I ; that is, with which half the redundant 

 fluid in both spaces is repelled by an equal quantity of 

 fluid. Therefore tjie pressure against Aa and HA de- 

 pends only on the quantity of redundant fluid in both 

 -paces together, and not at all on the thickness or dis- 

 tance of those spaces, or on the proportion in which 

 the fluid is divided between the two spaces. It' there 

 is no fluid in AH and GH, a particle placed on the 

 outside of the spaces AD and KlI, contiguous to the 

 planes Aa or lilt, is attracted toward* those planes by 

 all the matter in A B and GH, i. e. by all the redun- 

 dant matter in both spaces, and consequently endea- 

 vours to insinuate itself in the space AD or EH ; and 

 (he 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 Dd, and 



the force with which it doei 10, is that with which the Thwriltam! 

 redundant fluid in CD is '> the matter in IF. ' ' 



C not I If AD is overcbargad, and 1.11 mid.-,-- .T^T^"" 



.1, and the redundant fluid in AD i< ev:ctly sul- 

 lieiuit to saturate the redundant matter in Ell. all the l-ig. l 

 redundant fluid in AD will l>o rclleclcd in the space 

 CD, where it will be pressed close together: the space 

 1.1 will I" :' fluid, the quantity of 

 matter in it hi ing just cufficient to redun- 



dant fluid in CD, and the spares AC und'FH will be 

 every where satiu.i ides, if an opening is 



m. i. le in the planes Aa or ll/i, the fluid within the spa* 

 ce AD or 1.1 1 will ) . run out at it, 



nor will the fluid on the outsit. tdency to 



run in at it: a particle of fluid t.u. placed any whereon 

 t!ie outside of Ixrth >p;.ii ... a> r.l 1', will not lie at all at- 

 ,..(1 |.\ these space", any more than if' 

 they wero both saturated ; but a particle placed any 

 where Intu Celled 



from d towards r ; and if a communication w as made 

 between the two sp.-u.-, by t!.u e-nal ilc, the fluid 

 would run out of AD into 1.11, till they were both sa- 

 turated. 



In the following propositions, the bodies are suppo- 

 sed to consist of solid m itter, Confined to the same 

 spot, so us not to be able to alter its shape or situation 

 by the attraction or repulsion of other bodies on it : 

 the electric fluid in these bodies is supposed to be movi - 

 able, but unable to escape, nnV-s when otherwise < 

 pressed. As for the mutter in all the rest of the uni- 

 verse it is supposed to be saturated with ilnmoveabie 

 fluid. The electric attraction and repulsion is suppo- 

 i to be inversely as any power of the distance less 

 than the cube, except when otherwise expre.-sed. 



By a canal, he means a slender thread of matte- 

 siich kind that the electric iluid shall be able to move 

 readily along it, but shall not be able to escape from it, 

 except, at the. ends, where it communicates with other 

 bodies. Thus when he says that two bodies communi- 

 cate w ith each other by .1 canal, he means that the fluid 

 shall be able to pass readily from. one body to the other 

 by that canal. 



Pro/A VI I. If any body, at a distance from cm- over Titor. T. 

 or under charged body, be overcharged, the fluid with- 

 in it will be lodged in greater quantity near the surface 

 of the body than ne:ir the centre. Eor, if you supp . . 

 it to be spread uniformly all over the body, a particle of 

 fluid in it, near the surface, wilt be repelled towards the 

 surface by a greater quantity of fluid than that by which 

 it is repelled from it ; consequently the fluid will flow 

 towards the surface, ami make it denser there : more-, 

 over, the particles of fluid close to the surface will be 

 pressed close together; for otherwise, a particle placed 

 so ne.u- it, that the quantity of redundant fluid between 

 it ;md the surface should be very small, would nun e 

 towards it ; as the small quantity of redundant fluid be- 

 tween it and the surface would be unable to balance 

 the repulsion of that on the other side. 



From the two problems, it seems likely, that almost 

 all the redundant fluid in the body will be lodged close 

 to tlie surface, and there pressed close together, and the 

 rest of the body will be saturated. 



Carol. If the body is undercharged, the deficiency 

 of fluid will be greater near the surface than near the 

 centre, and the matter near the surface will be entirely 

 deprived of fluid. It is likely, too, that all parts, ex- 

 cept near the surface, will be saturated. 



Prop. VIII. Let the bodies A and D (Fig. 5.) com- PBor. 8. 

 municatc with each other by the cwial EF ; and let one Fig. J- 



