[68] See my communication on “Free Electricity,” in Silliman’s American Journal of Science, vol. iii., New Series, number for May, 1847.
[69] The sectional area of a conductor is the area of the superficies which would be exposed by cutting it through at right angles to its axis.
[70] 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.
[71] Suppose a number of boys and girls, associated as partners for a dance, to stand up in a row, severally united, and distinguished into couples by those joining hands; the sexes being regularly alternating, so that no two of the same sex should be hand in hand. Under these conditions no effort to take a boy from one end of the row, or a girl from the other end, could be effected with the consent of the couples concerned, both partners in which would thus be deprived of the power of joining in the dance. But should it be understood that only an exchange of partners was all that should be intended, and, consistently, a boy from one end and a girl from the other end of the row, taken simultaneously and allowed to form a couple, forthwith, the rest merely shifting their hands from one neighbour to another, there would no longer be the same motive for resistance and the required exchange might be cheerfully accomplished.
[72] By a void I mean a Torrecellian vacuum. The omnipresence of the electro-ether must render the existence of a perfect void impossible.
[73] It is well known that Wollaston effected the decomposition of water by the aid of a powerful electrical machine. Having enclosed platina wires within glass tubes, these were fused so as to cover the ends. The glass was afterward so far removed, by grinding, as to expose minute metallic points to the liquid. Under these circumstances, the electricity conveyed by the wires, being prevented from proceeding over them superficially, was obliged to make its way through the ethereo-ponderable matter of which metals consist. Instead of proving the identity of galvanism with frictional electricity, this experiment shows that in one characteristic, at least, there is a discordancy. At the same time it may indicate that ethereal may give rise to ethereo-ponderable undulations.
[74] Agreeably to experiments of Farraday, the particles of a glass prism may be as influenced by an electro-magnet as to affect the passage of polarized light.
[75] L. and E. Phil. Mag. and Jour., vol. xlv. p. 383, 1844.