372 Sir W. Snow Harris on the Laws and Operation [June 16, 



Charge of the rectangular plate surface =105 square inches, 7 circular 

 inches under an intensity of 10°. Charge of rectangular plate surface 200 

 square inches, 12 circular inches, under the same intensity of 10°. The 

 charges therefore are as 7:12 nearly, or as 1 : 1 • 7, being as the square 

 roots of the surfaces multiplied into the square roots of the boundaries 

 very nearly. 



Experiment 10. A square plate 10 inches square, surface 100 square 

 inches, boundary 40 inches, compared with a rectangular plate 40 inches 

 long by 5 inches wide, surface 200 square inches, boundary 90 inches. 



Here the surfaces are double of each other, and the boundaries also 

 double each other, or so nearly as to admit of their being considered 

 double of each other. Charge of square plate 6 circular inches, under an 

 intensity of 10°. Charge of rectangular plate 12 circular inches, under 

 the same intensity of 10°. The charges, therefore, are as the square roots 

 of the surfaces and boundaries conjointly, according to the formula 

 C= VS.B, as also verified in the preceding experiment 9. 



A double surface, therefore, having a double boundary, takes a double 

 charge, but not otherwise. Neglecting all considerations of the boundary, 

 therefore, the surface and boundary varying together, the charge in this 

 case will be as the surface directly. 



18. The author having verified experimentally the laws of surface and 

 boundary, as regards plane rectangular surfaces, proceeds to consider the 

 charges of square plates, circular plates, spheres, and closed and open sur- 

 faces generally. 



Experiment 11. Plate 10 inches square, surface 100 square inches, 

 boundary 40 inches, compared with a similar plate 14 inches square, sur- 

 face 196 square inches, boundary 56 inches. Here the surfaces are as 1 : 2 

 nearly, whilst the boundaries are as 1 : V 2 nearly. 



In this case charge of square plate, surface 100 square inches, was found 

 to be 8 circular inches under an intensity of 10°. Charge of the plate, 

 surface 196 square inches, 11 circular inches, under the same intensity of 

 10°. Here the charges are as 8 : 11, whilst the surfaces may be taken as 

 1 : 2, that is to say (neglecting the boundary), the charges are as the square 

 roots of the surfaces, according to the formula C= VS. 



On examining the intensities of these plates, they were found to be 

 inversely as the surfaces ; thus 8 circular inches upon the plate, surface 100, 

 evinced an intensity of 1 0° ; 8 circular inches upon the plate, surface 1 96, 

 evinced an intensity of 5° only, or | the former, according to the formula 



V 1 



^=s- 



Experiment 12. A circular plate of 9 inches diameter, surface 63*6 

 square inches, compared with a circular plate of 18 inches, or double that 

 diameter, surface 254 square inches. Here the surfaces are as 1 : 4, whilst 

 the boundaries or circumferences are as 1:2. 



Charge of 9-inch plate, 6 circular inches, under an intensity of 10°. 



