Yet in the experiment known as Hall's, the current is deflected by the magnetic field to one side of the strip in certain metals, and to the opposite side in others.

This seems to show that in certain cases the positive electrons move instead of the negative, and Professor Lorentz confesses that up to the present he can find no valid argument against this.

See _Archives Neerlandaises_ 1906, parts 1 and 2 .-- ED.] Sec.3.THE MASS OF ELECTRONS Other conceptions, bolder still, are suggested by the results of certain interesting experiments.

The electron affords us the possibility of considering inertia and mass to be no longer a fundamental notion, but a consequence of the electromagnetic phenomena.
Professor J.J.Thomson was the first to have the clear idea that a part, at least, of the inertia of an electrified body is due to its electric charge.

This idea was taken up and precisely stated by Professor Max Abraham, who, for the first time, was led to regard seriously the seemingly paradoxical notion of mass as a function of velocity.