Michael Faraday threw himself _con amore_ into the question. He set about to classify the pile phenomena, and arranged them with appropriate terms, and in a series of papers, between the years 1830 and 1840 (_see_ his “Experimental Researches”), he explained the chemical effects of voltaic electricity and electro-magnetic induction. He showed that the electricities obtainable from the voltaic pile and the electrical machine are essentially the same in their action. He proved that the theory held respecting the necessity for the presence of water in electro-chemical composition was erroneous, and that many other fluids and compounds were equally effective. We have not space at our disposal to include a digest of his various lectures and papers. He calculated that as much electricity is employed in holding the gases oxygen and hydrogen together in a grain of water, “as is present in a discharge of lightning.” When water is decomposed by the electric current, the force which determines the oxygen and acid matter held in solution to the positive, while the hydrogen passes to the negative pole, is not in the poles, but in the body decomposed, he says. “The poles,” writes Faraday, “are merely the surfaces or doors by which the electricity enters into or passes out of the decomposing substance. They limit the extent of that substance in the course of the electric current, being its termination in that direction. Hence the elements evolved passed so far and no farther.” Faraday named the poles “electrodes”—the way (in or out) of electricity. A very simple voltaic pile may be constructed with “gold-leaf” paper. Take two sheets of the gold paper and paste them back to back, and two of silver paper; cut them into discs about the size of a five-shilling-piece (or even of half-a-crown), and place them one on the top of the other, so as the gold and silver may be alternate; press the discs together slightly when a good many layers have been piled up, and introduce them into a glass tube; close the ends of the tubes with corks through which wires are passed from the discs top and bottom. It will be found that the ends are charged with opposite electricities. This is the _Zamboni_ pile, or the dry pile, which was constructed of hundreds of paper discs “tinned on one side, and covered with binoxide of manganese on the other,” put into a tube, and closed with brass stoppers. The electricity will last a long time in a dry pile. [Illustration: Fig. 221.—The Galvanic Pile.]