472 Dr. Hare's Second Letter to Prof. Faraday. 



poles of a magnel upon intervening pieces of iron wire. In 

 1679, 14th series, you suggest this as an analogous case to 

 that of the process of ordinary electrical induction, which we 

 have under consideration. Should there be in the one case, 

 a thousand pieces of wire interposed, in the second, a hundred, 

 will it be pretended that the intensity of their reciprocal in- 

 ductive reaction would be inversely as the number; so that 

 the effect of the last-mentioned number of wires would be 

 equivalent to that of the first ? Were intervals to be created 

 between the wires, by removing from among the number first 

 mentioned alternate wires, it would seem to me that the 

 energy of their reciprocal influence would be diminished, not 

 only as the number of them might be lessened, but also as 

 they should consequently be rendered more remote. 



57. If, as you suggest, the interposition of ponderable par- 

 ticles have any tendency to promote inductive influence (H), 

 there must be some number of such particles by which this 

 eflPect will be best attained. That number being interposed, 

 I cannot imagine how the intensity of any electro-polarity, 

 thus created in the intervening particles, can, by a diminution 

 of their number, acquire a proportionable increase ; and evi- 

 dently in no case can the excitement in the particles exceed 

 that of the " inductric" surfaces, whence the derangement of 

 electrical equilibrium arises. 



58. The repulsive power of electricity being admitted to be 

 inversely as the squares of the distances, you correctly infer, 

 that the aggregate influence of an electrified ball B, situated 

 at the centre of a hollow sphere C, will be a constant quan- 

 tity-, whatever may be the diameter of C. This is perfectly 

 analogous to the illuminating influence of a luminous body 

 situated at the centre of a hollow sphere, which would of 

 course receive the whole of the light emitted, whatever might 

 be its diameter ; provided that nothing should be interposed 

 to intercept any portion of the rays. But in order to answer 

 the objection which I have advanced, that the diminution of 

 the density of a " dielectric" cannot be compensated by any 

 consequent increase of inductive intensity, it must be shown, 

 in the case of several similar hollow spheres, in which various 

 numbers of electrified equidistant balls should exist, that the 

 influence of such balls upon each other, and upon the surfaces 

 of the spheres, would not be directly as the number of the 

 balls, and inversely as the size of the containing spaces. 

 Were gas-lights substituted for the balls, it must be evident 

 that the intensity of the light in any one of the spheres would 

 be as llie number of lights which it might contain : now one 

 of your illustrations (8), above noticed, makes light and elec- 



