Sir W. Snow Harris’s Researches in Statical Electricity. 179 
meter very differently, notwithstanding that the surface is the 
same in each. And in order to give to the electrometer the same 
indication, different quantities will be required. Thus, if five 
measures communicated to the sphere indicate 10 degrees of 
force, seven measures will be required to be disposed on the plate 
to indicate the same force: for the rectangle some other number 
will be required. The number of measures thus requisite to 
bring the electrometer index to the same point, is the electrical 
charge of the given conductor as accepted by Cavendish, and 
may be supposed to represent the electrical capacity of any given 
surface. 
26. This understood, we may now proceed to consider an in- 
teresting and beautiful experiment by Coulomb, on the relative 
charges of a hollow sphere and a circular plate of twice the dia- 
meter ; from which it has been inferred that the plate charges 
in proportion to its two surfaces, and the sphere only in propor- 
tion to its outer surface. There can be but little doubt of the 
perfect accuracy of the experiments of this most ingenious and 
profound philosopher, nevertheless I am led to believe that they 
admit of a somewhat different interpretation from that generally 
given to them. 
Exp. 15. Take two equal spheres, A, B, fig. 22, and a plate, 
P, of twice the diameter of the sphere ; charge one of the spheres 
A with a given quantity of electricity, and subsequently touch it 
with the insulated plate P. The charge by the method of Cou- 
lomb will be found shared between the sphere and plate in the 
proportion of 1:2; that is to say, the plate will have abstracted 
two-thirds of the charge, and will have left one-third. Now, as 
already observed, although there can be little doubt of the accu- 
racy of this result as stated by Coulomb, yet the sharing the 
charge between these bodies is not the same thing as charging 
the bodies separately with measured quantities of electricity (25). 
if we attempt to place a unit of quantity on the sphere, and twice 
that quantity on the plate under the same degree of the electro- 
meter, we fail to do it: the plate will not receive it. And we 
have just seen (23), Exp. 14, that when a plate really takes up 
electricity as charge in proportion to both its surfaces, we then 
have a double accumulation, and we can place the same quan- 
tity of electricity on each surface as compared with a given 
unit of quantity. Now in the sharing of the charge between 
the sphere and plate, the plate would necessarily appropriate 
to itself an amount of electricity proportionate to the free in- 
ductive aetion between it and the sphere: in fact, as may be 
clearly seen, its remote surface P is twice that of the remote 
surface p of the sphere, and consequently has twice the direct 
induetive capacity, so that the near face would be in a position 
N 2 
