Capacities of bodies of various forms determined 145 



280] The charges of the two small wires at the several distances of 

 36, 24, and 18 inches ought by theory to have been to that of the long 

 wire in a proportion between that of -923, -905, and -883 to i and that 

 of -893, -860, and -835 to i, supposing them to be connected to the vial 

 by canals of incompressible fluid, but, as it should seem from the next 

 experiment, ought in all probability to approach much nearer to the 

 former proportion than the latter. The observed charges were actually 

 between these two proportions, but approached much nearer to the latter, 

 so that they agreed as nearly with the computation as could be expected*. 



281] Exp. VII. Being a comparison of the proportional charges of 

 several bodies of different shapes: the result is as follows: 



A globe 12-1 inch in diameter i-ooo 



A tin circle 18-5 ,, -992 



A tin plate 15-5 inches square -957 



An oblong tin plate 17-9 inches by 13-4 inches . . -965 

 A brass wire 72 inches long and -185 thick . . -937 

 A tin cylinder 54-2 inches long and -73 in diameter . -951 

 A tin cylinder 35-9 inches long and 2-53 in diameter -999 

 The globe was the same that was used in the first experiment. The 

 wire and cylinders were placed in the same manner as the large wire in 

 the preceding experiment, and were touched in the same manner f. 



282] Remarks on this experiment. 



First, the proportion which the charge of the circular plate bears to 

 that of the globe agrees very well with the theory, for by Prop. XXIX 

 [Art. 140] the proportion should be between that of -76 to i and that of 

 1-53 to i, and the observed proportion is that of -992 to i. We may 

 conclude also from this experiment that the charge of a circular plate is 

 to that of a globe of the same diameter as 12 to i8, which by the above- 

 mentioned proposition is the proportion which ought to obtain if ^f of 

 the whole quantity of redundant fluid in the plate was spread uniformly 

 [over the surface] , and the remainder, or ^\, was spread uniformly [round 

 the circumference], that is, if the value of p in that proposition equals |f {. 



283] 2ndly. The charge of a square plate is to that of a circle whose 

 diameter equals the side of the square, as 1-153 to I, or its charge is to that 

 of a circle whose area equals that of the square as 1-02 to i. 



284] 3rdly. The charge of the oblong plate is very nearly equal to 

 that of a square of the same area, and consequently as the length of the 

 trial plates used in these experiments never differed from their breadth 

 (whether the trial plate was more or less drawn out) in a greater proportion 

 than those of this oblong plate do, and as the charges of similar bodies 



* [Arts. 453, 476, 477, 683, and Note 13.] t [Arts- 4?8, 682.] 



J [Arts. 654, 68 1, and Note 2.] [Arts. 479, 682, and Note 22.] 



c. p. i. 10 



