Page:A history of the theories of aether and electricity. Whittacker E.T. (1910).pdf/104

 up a great number of knives and forks in a large box, and having placed the box in the corner of a large room, there happen'd in July, 1731, a sudden storm of thunder, lightning, etc., by which the corner of the room was damaged, the Box split, and a good many knives and forks melted, the sheaths being untouched. The owner emptying the box upon a Counter where some Nails lay, the Persons who took up the knives, that lay upon the Nails, observed that the knives took up the Nails."

Lightning thus came to be credited with the power of magnetizing steel; and it was doubtless this which led Franklin in 1751 to attempt to magnetize a sewing-needle by means of the discharge of Leyden jars. The attempt was indeed successful; but, as Van Marum afterwards showed, it was doubtful whether the magnetism was due directly to the current.

More experiments followed. In 1805 Jean Nicolas Pierre Hachette (b. 1769, d. 1834) and Charles Bernard Desormes (b. 1777, d. 1862) attempted to determine whether an insulated voltaic pile, freely suspended, is oriented by terrestrial magnetism; but without positive result. In 1807 Hans Christian Oersted (b. 1777, d. 1851), Professor of Natural Philosophy in Copenhagen, announced his intention of examining the action of electricity on the magnetic needle; but it was not for some years that his hopes were realized. If one of his pupils is to be believed, he was "a man of genius, but a very unhappy experimonter; he could not manipulate instruments. He must always have an assistant, or one of his auditors who had easy hands, to arrange the experiment."

During a course of lectures which he delivered in the winter of 1819-20 on "Electricity, Galvanism, and Magnetism," the idea occurred to him that the changes observed with the compass-needle during a thunderstorm might give the clue to the effect of which he was in search; and this led him to think that the experiment should be tried with the galvanic circuit