Note 70 — APPENDIX.
Reading edition
According to Colomb’s experiments, electrical attraction and repulsion are inversely as the squares of the distances: ought not the inductive power of statical charges which is produced by those forces, and which precedes and determines the length of the resulting spark, to obey the same law?
If this calculation be correct, the intensity must be as the squares of the striking distances, as indicated by sparks.
It may be urged that the striking distances, as measured by the length of the sparks, is in the compound ratio of the quantity and intensity. As to the quantity, however, galvanic sources have always been treated as pre-eminent in efficacy, so that on that side there could be no disparity. Moreover, I have found, that in galvanic apparatus of only one, or even of two pairs, as in the calorimotors, the intensity lessened as the surfaces were enlarged. By a pair of fifty square feet of zinc surface, a white heat could not be produced in a wire of any size, however small. The calorific power of such apparatus can only be made evident by the production of a comparatively very low temperature, in a comparatively very large mass.