Nothing then remained in order to maintain this hypothesis, except to deny the convection, which, besides, was only established by indirect experiments.

That the reality of this transport has been placed beyond dispute by means of an extremely elegant experiment which is all the more convincing that it is so very simple, is due to M.Perrin.In the interior of a Crookes tube he collected a pencil of cathode rays in a metal cylinder.

According to the elementary principles of electricity the cylinder must become charged with the whole charge, if there be one, brought to it by the rays, and naturally various precautions had to be taken.

But the result was very precise, and doubt could no longer exist--the rays were electrified.
It might have been, and indeed was, maintained, some time after this experiment was published, that while the phenomena were complex inside the tube, outside, things might perhaps occur differently.

Lenard himself, however, with that absence of even involuntary prejudice common to all great minds, undertook to demonstrate that the opinion he at first held could no longer be accepted, and succeeded in repeating the experiment of M.Perrin on cathode rays in the air and even _in vacuo_.
On the wrecks of the two contradictory hypotheses thus destroyed, and out of the materials from which they had been built, a theory has been constructed which co-ordinates all the known facts.