It would also appear from the motions of the magnet, when differently placed with regard to the uniting wire, that this energy circulates, or performs a circular movement around the axis of the conductor, and thus drives the magnetic pole according to the direction of the needle with reference to such a current.
This important discovery was no sooner announced to the philosophical world, than Sir Humphry Davy, with his characteristic zeal, proceeded to repeat the experiments; and, with his usual sagacity, so to vary and extend them, as to throw new light upon this novel department of science. The facts he thus discovered, and the reasonings founded upon them, were communicated by him to the Royal Society in three successive memoirs.
The First, "On the Magnetic Phenomena produced by Electricity," was read on the 16th of November 1820.
The Second, entitled "Farther Researches on the Magnetic Phenomena produced by Electricity; with some new Experiments on the properties of Electrified bodies, in their relations to conducting powers and Temperature," read July 5th, 1821.
The Third, "On a new Phenomenon of Electro-magnetism," read March 6th, 1823.
The principal experiments communicated in these memoirs were performed with the battery belonging to the London Institution,[72] the once powerful apparatus at the Royal Institution having become old and feeble in his service.
The following letter contains an invitation to his friend Mr. Pepys, to witness his first experiment; a document so far valuable, as it fixes a date of some importance in the history of discovery.
TO WILLIAM HASLEDINE PEPYS, ESQ.
Grosvenor Street, Oct. 20, 1820.
DEAR PEPYS,