142 Capacities of disks as modified by approach 



them and the trial plate; Ee is the large circle placed half way between 

 the two small ones, and Rr the wire by which it is electrified. . But it must 

 be observed, that in trying the large circle the two small circles and the 

 wires Rf and Rg are taken away and the wire Rr put in their room ; and 

 in like manner, when the small circles are tried, the circle Ee and the wire 

 Rr are removed. 



274] It must be observed that the charge of the two small circles 

 together will not be as much as double the charge of one circle, unless 

 the distance of the two circles from each other is extremely great. In 

 order, therefore, to know better what allowance to make on this account, 

 I tried the experiment with the two small circles placed at three different 

 distances, namely, at 18, 24, and 36 inches from each other, the circles 

 being always placed so that the middle point between them was at the 

 same distance from D. Their charges came out in the following propor- 

 tion * : 



The large circle i-ooo, 



The two small ones at 36 inches distance '899, 



24 -859, 



,, ,, ,, 18 ,, -811. 



275] I repeated the experiment in the same manner, except 1st, that 

 the distances of the vials from the circles and trial plate were different 

 from what they were before, namely, in the foregoing experiment the 

 distance To, from the middle of the trial plate to the vial a was 87 inches 

 and eA, or the distance from the center of Ee to the vial A, was 106 inches, 

 whereas in this experiment Ta was 98 inches and eA 63 inches; the 

 distance Te was 83 inches in both experiments ; and 2ndly, that I placed 

 a frame of wood about 5 feet square under the circles 14 inches from the 

 ground. The reason of these alterations will be shewn by and byf. Their 

 charges came out as follows: 



The large circle i-ooo, 



The two small ones at 36 inches distance '894, 



24 -840, 



18 -798. 



276] Let us now endeavour to find out what proportion the charges 

 ought to bear to each other by the theory on the above-mentioned sup- 

 position of their being connected by canals of incompressible fluid, and 

 of the electrical attraction and repulsion being inversely as the square of 

 the distance. This cannot be done exactly without knowing the manner 

 in which the redundant fluid is disposed in the circles, which I am not 

 acquainted with, but if we suppose the fluid to be spread uniformly over 



* [Arts. 452, 454, 472-475.]. 



f [Arts. 277, 339, 474 and Note 17.] 



