402 Note 1 8: Cavendish's earliest theory 



COR. Let C be a conductor of electricity of any shape, em and fn wires 

 extending from thence to a great distance. Let a and b be two equal bodies 

 placed on those wires at such a distance from C as not to be sensibly affected 



C 



by the electricity thereof, and let the conductor or wires be electrified by any 

 part: the quantity of electric fluid in the bodies a and b will not be sensibly 

 different, or they will appear equally electrified. 



Case i. Let the parallel planes Aa, Bb, &c., be continued infinitely. Let 

 all infinite space except the space contained 

 between A a and Cc, and between Ee and Hh, A 



be filled uniformly with particles repelling in- c 



versely as the square of their distance; let the 3| 



space between Ee and Hh be filled with fluid 

 of the same density, the particles of which can 

 move from one part to another; and let the 



space between Aa and Cc be filled with matter o SL 



whose density is to [that in] the rest of space h 



as AD to AC. 



Take EF = JCD, and GH such that the matter between Ee and Ff when 

 pressed close together, so that the particles touch each other, shall occupy the 

 space between Gg and Hh. 



The space between Ee and Ff will be a vacuum, that between Ff and Gg 

 of the same density as the rest of space ; and between Gg and Hh the particles 

 will touch one another. 



Case 2. Let everything be as in case the first, except that there is a canal 

 opening into the plane Hh, by which the matter in the space EH is at liberty 

 to escape; part of the matter will then run out, and the density therein will 

 be everywhere the same as without, except in the space EF, which will be 

 a vacuum, EF being equal to CD. 



Case 3. Suppose now that a canal opens into the plane Aa by which the 

 fluid hi the space AC may escape. It will have no tendency to do so, for the 

 repulsion of the redundant fluid in A C on a particle at a will be exactly equal 

 to [the] want of repulsion of the space EH. 



Case 4. Let now the space between Aa and Cc be filled with matter whose 

 density is to the rest of space as AB to AC. 



Then the space between Hh and Gg will be a vacuum, GH being equal to 

 JBC. In the space EF the particles of matter will be pressed together so as 

 to touch each other, the quantity of matter therein exceeding what is naturally 

 contained in that space by as much as is driven out of the space GH ; and in 

 the space between Ff and Gg the matter will be of the same density as without. 





