It was in 1834 that Mr. Wm. Jenkin, after one of the Friday evening lectures at the Royal Institution, called the attention of Faraday to a shock which he had experienced in breaking the circuit of an electro-magnet, though the battery employed consisted of only one pair of plates. Faraday repeated the experiment, and found that, with a large magnet in circuit, a strong spark could thus be obtained. On November 14, 1834, he writes, "The phenomenon of increased spark is merely a case of the induction of electric currents. If a current be established in a wire, and another wire forming a complete circuit be placed parallel to it, at the moment the current in the first is stopped it induces a current in the same direction in the second, itself then showing but a feeble spark. But if the second be away, it induces a current in its own wire in the same direction, producing a strong spark. The strong spark in the current when alone is therefore the equivalent of the current it can produce in a neighbouring wire when in company." The strong spark does, in fact, represent the energy of the current due to the self-induction of its circuit, which energy would, in part at least, be expended in inducing a current in a neighbouring wire if such existed. His time from 1835 till 1838 was largely taken up with his work on electro-static induction. Faraday could never be content with any explanation based on direct action at a distance; he always sought for the machinery through which the action was communicated. In this search the lines of magnetic force, which he had so often delineated in iron filings, came to his aid. Faraday made many pictures in iron filings of magnetic fields due to various combinations of magnets. He employed gummed paper, and when the filings were arranged on the hard gummed surface, he projected a feeble jet of steam on the paper, which melted the gum and fixed the filings. Several of his diagrams were exhibited at the Loan Collection at South Kensington. He conceived electrical action to be transmitted along such lines as these, and to him the whole electric field was filled with lines passing always from positive to negative electrification, and in some respects resembling elastic strings. The action at any place could then be expressed in terms of the lines of force that existed there, the electrifications by which these lines were produced being left out of consideration. The acting bodies were thus replaced by the field of force they produced. He showed that it was impossible to call into existence a charge of positive electricity without at the same time producing an equal negative charge. From every unit of positive electricity he conceived a line of force to start, and thus, with the origin of the line, there was created simultaneously a charge of negative electricity on which the line might terminate. By the famous ice-pail experiment he showed that, when a charged body is inserted in a closed