"And though your good opinion has, as it were, honoured me with a rank similar to that of General, I shall be always happy to act as a private soldier in the ranks of Science."
Many years before even the identity of lightning and electricity was suspected, it had been observed, on several occasions, that the magnetism of the compass needle was not only destroyed, which might have been attributed to heat, but that it was even reversed by lightning.[67]
In the progress of electrical discoveries, the similarity between electricity and magnetism had not escaped observation,[68] and some philosophers had even attempted to establish the existence of an identity or intimate relation between these two forces. The experiments of Ritter, however, alone appeared to offer any confirmation of the supposed analogy; but so obscure was his language, and so wild and hypothetical his views, that few, if any, of them were repeated either in France or England, and their results were for a long time wholly disregarded.
In a work, entitled "Recherches sur l'identité des Forces Chimiques et Electriques," published by M. Oersted in the year 1807, the subject was resumed, and the author advanced the hypothesis,[69] which twelve years afterwards conducted him to one of the most important discoveries of the present age, and which has given origin to a new science, termed Electro-magnetism.[70]
In the winter of 1819, Professor Oersted, Secretary to the Royal Society of Copenhagen, published an account of some experiments, in which the electric current, such as is supposed to pass from the positive to the negative pole of a Voltaic battery, along a wire which connects them, caused a magnetic needle near it to deviate from its natural position, and to assume a new one, the direction of which was observed to depend upon the relative position of the needle and the wire.[71]
It may be necessary to premise, that these experiments were conducted in a form which had never before suggested itself to the enquirer; viz. with the two ends of the pile in communication with each other,—a condition which enabled it to discharge itself freely: this circumstance will, at once, explain the reason of all preceding failures. It was never before suspected that the electric current, passing uninterruptedly through a wire, connecting the two ends of a Voltaic battery, was capable of being manifested by any effect; the experiments, however, in question furnished an unequivocal test of its passage by its action on the magnetic needle; and which may be shortly stated as follows:
The opposite poles of a battery, in full action, were joined by a metallic wire, which, to avoid circumlocution, has been called the uniting conductor, or the uniting wire.
On placing the wire above the magnet and parallel to it, the pole next the negative end of the battery always moved westward, and when the wire was placed under the needle, the same pole went towards the east. If the wire was on the same horizontal plane with the needle, no declination whatever took place, but the magnet showed a disposition to move in a vertical direction; the pole next the negative side of the battery being depressed when the wire was to the west of it, and elevated when it was placed on the east side.
The extent of the declination occasioned by a battery, depends upon its power, and the distance of the uniting wire from the needle. If the apparatus is powerful, and the distance small, the declination will amount to an angle of forty-five degrees or more; but this deviation does not give an exact idea of the real effect which may be produced by galvanism; for the motion of the needle is counteracted by the magnetism of the Earth. When the influence of this latter power is destroyed by means of another magnet, the needle will place itself directly across the connecting wire: so that the real tendency of a magnet is to stand at right angles to an electric current. Such phenomena, being wholly at variance with the laws of simple electrical attraction and repulsion, are only to be explained upon the supposition that a new energy is generated by the action of the current of electricity thus brought into conflict, and which must be identical with, or nearly related to, magnetism.