{IV.} WHETHER THE FORCE WITH WHICH TWO BODIES 

 REPEL IS AS THE SQUARE OF THE REDUNDANT FLUID, 

 TRIED BY STRAW ELECTROMETERS*. 



[From MS. N. 8: hitherto unpublished. See Table of Contents at the 

 beginning of this volume.] 



386] If two bodies, A and B, placed near to each other, are both 

 connected to the same overcharged Leyden jar, and the force with which 

 this jar is electrified is varied, everything else remaining unaltered, the 

 force with which A and B repel each other ought by the theory to be as 

 the square of the quantity of redundant fluid in the jar, supposing the 

 distance of the bodies A and B to remain unaltered. For the quantity 

 of redundant fluid in A is directly as the quantity of redundant fluid in 

 the jar, and therefore the force with which each particle of redundant 

 fluid in B is repelled by A is also directly as the quantity of redundant 

 fluid in the jar, and therefore as the number of particles of redundant 

 fluid in B is also as the quantity of redundant fluid in the jar, the force 

 with which B is repelled by A is as the square of the quantity of redundant 

 fluid in the jar. 



387] In order to try whether this was the case, I made use of the 

 following apparatus f . 



CD (Fig. 31) is a wooden rod 43 inches long, covered with tinfoil and 

 supported horizontally by non-conductors. At the end C is suspended, as 



Fig. 31. 



in the figure, the electrometer described in Art. 249, and at the other end D 

 is suspended a similar electrometer, only the straws reached to the bottom 

 of the cork balls A and B, but not beyond them, and were left open so 

 as to put in pieces of wire, and thereby increase their weight and the 

 force with which they endeavoured to close. The lower ends of these 



* [Title supplied from Cavendish's Index to {the results ofj his experiments. 

 Art. 563.] 



f [Arts. 563, 567, also Art. 525.] 



