[35] This communication, as well as those immediately preceding and following it, would have been inserted under the head of Corroborative Evidence, page 55, &c., had they been received in time.
[36] [According to my spirit friends, this earth forms one of them, the first; so that there are six spirit spheres.]
[37] Andrew Jackson Davis.
[38] Wood-cuts of the characters alluded to in this and the succeeding paragraphs, may be seen in Mr. Capron’s book.
[39] “Mr. Sunderland, in his ‘Book of Human Nature,’ p. 280, says this was the first of the spirit writing, but Mr. Capron alleges that he was acquainted with cases of this kind long before the disturbances at Stratford.”
[40] Latterly, Sir David Brewster has conceived that only three elementary species of light are requisite, according to the theory of emission, to perform all the offices which Newton ascribed to seven.
[41] It should be understood, that when two magnetic needles are associated by the contact of dissimilar poles, the extreme poles do not lose their magnetism, although it will be more feeble than when the needles are independently situated.
[42] Explanation of the Galvanic Pile, Battery, or Series.—When pieces of zinc and silver are so placed in the mouth as to have their surfaces separated by the tongue, their extremities extending beyond it externally, on allowing the latter to touch each other, a metallic taste is perceived by the person whose tongue is subjected to the process thus described. It has been ascertained that at the same time a minute portion of the zinc is oxydized at the expense of the water which exists in the saliva.
Suppose a pile of plates of zinc and silver, or copper, alternating, to be separated into couples by the interposition of moistened cloth; each plate will on one side touch its partner, on the other side the moistened cloth. Every couple of zinc and copper separated by the cloth are situated as the pair above described, when separated by the tongue, and are equally capable of giving a discharge which would be sensible to the taste, under those circumstances. The plates which are in metallic contact have no such disposition to discharge, because there is no moisture to act upon them, and no diversity of electrical state can be excited on account of their great conducting power, which would neutralize any such excitement as soon as it could be created. The surfaces separated by the cloth cannot discharge to each other, because there is no conductor extending from one to the other. But as the whole pile is a conductor of electricity, to discharge every pair entering into its constituency it is only necessary to touch each end simultaneously with a good conductor—a wire, for instance. The whole series will then be discharged at once, and the energy of the discharge is proportional to the number to be thus discharged. There is an uncertainty and obscurity as to the precise rationale of the effect thus obtained. There is as much difference about this as there is about the nature of matter. It will not be expedient, therefore, in presenting a popular view, to enter upon that intricate question, and will be enough to state the laws and facts which are admitted generally by men of science. It is universally admitted that, if each of the terminal plates, in such a pile or series, have a platina wire soldered or otherwise well connected with it, the other ends of the wires extending into some water, this liquid will be decomposed, and a similar decomposition may, directly or indirectly, be effected of various substances held in solution by water, as well as substances liquified by heat. Moreover, when the same wire is made to form the means of discharge by extending from one terminal plate to the other, it acquires the property of attracting iron filings, and, so long as the discharge through it is sustained, will cause the compass needle to arrange itself always at right angles to the wire. Under these circumstances, according to the Franklinian theory, a current of electricity passes from the positive to the negative pole; according to the theory of Dufay, a fluid proceeding from each pole, they combine in the wire. According to the view above given, two opposite waves of polarization pass, by which the metallic atoms or particles are shifted from their natural position, so as to act externally, as already stated.
It is not, I believe, known to whom the world is indebted for the fundamental observation in galvanism, made, as has been mentioned, by the assistance of the tongue and plates of silver and zinc. Subsequently, Galvani, probably without any reference to this phenomenon, ascertained some other consequences of the reaction of the elementary pair; but to Volta we owe the pile or series above described. In whatever form voltaic series may have been subsequently constructed, the main principles are the same, the reaction of chemical agents so arranged in succession as to be productive of that intensity of discharge, and powers of decomposition, to which allusion has been made.