anticipated instead of being required--_i.e._ if the currents could be formed _before_ the magnet came over the place instead of _after_--the effect would equally ensue. Adieu, dear Phillips. Excuse this egotistical letter from yours very faithfully, M. FARADAY. The second section shows that Faraday had discovered the cause of all the previous failures to evoke electric currents in wires by means of a magnet: it required _relative motion_. What the magnet at rest fails to do, the magnet in motion accomplishes. This crucial point is admirably commemorated in the following impromptu given by Mr. Herbert Mayo to Sir Charles Wheatstone:-- Around the magnet Faraday Was sure that Volta’s lightnings play: But how to draw them from the wire? He took a lesson from the heart: ’Tis when we meet, ’tis when we part, Breaks forth the electric fire. Faraday’s holiday was brief; by December 5 he was again at work on his researches. He re-observed the directions of the induced currents about which, as the slip in his letter to Phillips shows, his mind was in some doubt. Then on December 14th comes the entry:--“Tried the effects of terrestrial magnetism in evolving electricity. Obtained beautiful results.” “The helix had the soft iron cylinder (freed from magnetism by a full red heat and cooling slowly) put into it, and it was then connected with the galvanometer by wires eight foot long; then inverted the bar and helix, and immediately the needle moved; inverted it again, the needle moved back; and, by repeating the motion with the oscillations of the needle, made the latter vibrate 180°, or more.” The same day he “made Arago’s experiment with the earth magnet, only no magnet used, but the plate put horizontal and rotated. The effect at the needle was slight but very distinct.... Hence Arago’s plate a new electrical machine.” [Sidenote: POINTS IN THE DISCOVERY.]