The transit of ions in the electric arc

According to the most modern view, as enunciated by Professor J. J. Thomson in one of his recent works,* the phenomenon known as the Electric Arc is explained on the assumption that the positive and negative electrodes emit respectively positively and negatively electrified corpuscles or ions, which, under the influence of electric repulsion, travel across the space occupied by the arc and bombard the electrode opposite to the one from which they have been emitted. It is further supposed that the electric current is itself conveyed by these ions, and that the high temperature of the electrodes is produced by their bombardment. About a year ago it occurred to the writer that it should be possible to test the correctness of, at any rate, some portion of this theory by deflecting—by means of a magnet—either the positive or the negative ions into a Faraday cylinder placed with its aperture just touching the centre of the arc, in a manner somewhat similar to that adopted by Perrin, for demonstrating the electric charge carried by cathode rays. The experiment was tried, but it was found that no definite results could be obtained, owing to the erratic behaviour of the arc, which proved very unmanageable, and preferred to divide itself into two arcs between the carbon electrodes and the exterior of the Faraday cylinder, which was rapidly destroyed by fusion.