434 
MR. HARRIS ON THE ELEMENTARY LAWS OF ELECTRICITY. 
insulated and similar bodies equally charged, we may conclude that they always 
occur, to a greater or less extent, at some point or other, as the distance is varied. 
They will, however, as already observed, be most prominent under circumstances the 
most favourable to the inductive influence : and it is hence not surprising that the 
law of action should appear by experiment to be sometimes in an inverse ratio of the 
distance ; at others in an inverse ratio of the squares of the distances, and in others 
not conformable to either ; whilst in some instances we observe the singular pheno- 
mena of attraction at one distance and repulsion at another. 
19. One condition favourable to the disturbances above mentioned, and which it 
is important to notice, is the inequality of the repelling bodies in respect of extension, 
an increase of extension being generally accompanied by an increased inductive 
susceptibility. Thus it may be observed, that in connecting an insulated sphere, S, 
fig. 9, or other body, with the fixed ball of the balance, we give it so much inductive 
power that it is only in very few cases we obtain a repulsive force varying as not- 
withstanding the intensity of the opposed discs is considerable : in this case the re- 
sults will be often irregular, and the respective forces very frequently as 3 : 1 ; when 
the distances are as 2 : 1, in a great variety of cases the force will be found to vary 
i 
aS ~d' 
Experiment F. — An experimental illustration of this may be seen in the following 
Table. In these experiments the fixed ball p , fig. 3, was connected with an insulated 
sphere of three inches diameter ; the respective forces being the result of different 
charges, and being obtained by means of the micrometer circle, according to the 
method explained in section 12. 
Table V. 
Distance. 
Force. 
Distance. 
Force. 
Distance. 
Force. 
Distance. 
Force. 
Distance. 
Force. 
Distance. 
Force. 
4 
18 
4-5 
110 
10 
65 
13 
78 
17-5 
117 
20 
150 
8 
8 + 
9 
54 
20 
20 
26 
26 
35 
35 
26 
90 
. . . . 
.... 
18 
18 
.... 
.... 
.... 
.... 
40 
40 
— 
— 
— 
— 
— 
— 
— 
— 
52 
23 + 
A 
B 
c 
D 
E 
F 
We here perceive, in accordance with the preceding phenomena, that in column A, 
i 
where the intensities are not considerable, and the distances small, the force is as , 
or very nearly so ; whereas in column F, in which the intensities are considerable, and 
the distances great, we have the force nearly as -j 2 . In the other columns, B, C, D, E, 
the forces are nearly as 3 : 1 when the distances are as 2:1, except in one case in 
