192 Repulsion with Different Degrees 



parison of that in the vial*, and consequently it appears that the distance 

 to which the electrometer with the wires in it separates with a given 

 quantity of redundant fluid in the vial is very nearly the same as that to 

 which it separates without the wires when there is only half that quantity 

 of redundant fluid in the vial. 



Therefore as the force with which the electrometer endeavours to close 

 by its weight when the wires are in is to that with which it endeavours 

 to close without the wires as 3-9 to i, it appears that the force with which 

 the balls of the electrometer are repelled with a given quantity of re- 

 dundant fluid in the vial, is to that with which they are repelled when 

 there is only half that quantity of redundant fluid in the vial as 3-9 to i 

 (supposing the distance of the balls to be the same in both cases), that is, 

 very nearly as the square of the quantity of redundant fluid in the vial, 

 the difference being not more than what might very easily be owing to 

 the error of the experiment. So that the experiment agrees very well 

 with the theory. 



392] It was found that if the communication was made between the 

 two vials by a piece of metal, the electricity was diminished so suddenly 

 as to set the straws a vibrating, and it was some time before they stopt, 

 for which reason the communication was made by a piece of moist wood, 

 which, though it communicates the electricity of one vial to the other very 

 quickly, did not do it so instantaneously as to make the straws vibrate 

 much. 



393] The electricity of the vial was found to waste very slowly, so 

 that it could not be sensibly diminished during the small time spent in 

 communicating the electricity from one vial to the other and reading off 

 the divisions, so that no sensible error could proceed from that cause. 



394] I tried the experiment before in the same manner, and with the 

 same electrometers, except that the straws were not gilt, but only moist- 

 ened with salt. It then seemed as if the force with which the balls of the 

 electrometer were repelled with a given quantity of redundant fluid in 

 the vial was to that with which they were repelled with only half that 

 quantity in the vial as 4 to . 



As I suspected that this small difference from the theory was owing 

 to the straws not conducting sufficiently readily, I gilt the straws, when, 

 as was before shewn, the experiment agreed very well with theory. 



It must be observed that if the straws do not conduct sufficiently 

 readily, the balls of the electrometer will not be so strongly electrified 



* [In a sentence which Cavendish has scored out in his MS. we read ] 

 The charge of the two vials together was found to be 2168 inches. The diameter 

 of the rod CD was at a medium about J of an inch. [This would make the com- 

 puted charge of the rod 9-7 inches. En.] 



