transmission of motion through a vacuum; to extend its importance as the substratum of all phenomena it must become heterogeneous and capable of deformation; to form a neutral atom, some of it must become a spherical jelly in which other parts of itself are imbedded as rigid particles. It has, consequently, different degrees of hardness, and is subject to internal attractions. Thomson even volunteers the admission that, for the explanation of certain phenomena, his ether must have structure, or, at least, be stratified.
This can, of course, be no insinuation against the work of some of the greatest living physicists and mathematicians: accepting their premises, I do not doubt that they have drawn the consequences in the most rigid fashion. I do assert, however, that some of their fundamental terms are used in a different sense from that to which we are accustomed, and that we are, therefore, entitled to doubt whether the conclusions which they reach really affect the phenomena with which the chemist deals: as if one were to discuss the crystallographic structure of Pentelian marble with reference to the architecture of the Parthenon.
A few examples, pertinent to our inquiry, will more precisely establish my meaning. One of the fundamental postulates of Professor Thomson's mathematical argument is the definition of momentum as the product of mass by velocity. Although this is not axiomatic, we accept it as such by reason of the many ballistic experiments which have proved its truth, so long as the projectile's mass was assumed to remain constant: we should hesitate if we were told that mass was to vary, i. e., that a bullet which weighs the same before and after the shot, was heavier during its flight. But the momentum of Thomson's electrons increases faster than their velocity, when the latter approaches that of light; hence, he says, the mass of the electrons increases with their swiftness. True, he calls it an electro-magnetic mass, but some of his followers have forgotten the distinction. At all events, his terms momentum and mass must not be accepted by us in their usual meaning.
It is perfectly true that Thomson's calculations are corroborated by Kaufmann's experiments on the velocity of radium rays in combined electric and magnetic fields, if the latter's data are calculated according to Thomson's views; without even seeking a radically different basis—which would not be difficult—we can follow Thomson to a point where his departure from ordinary assumptions becomes evident. He shows that the value e/m diminishes at high velocities and then he assumes that e, the electro-static charge, is constant; therefore m, the mass, varies. Now, the value of e is derived from Faraday's law, which would never have been announced if Faraday had not dealt with the equivalent weights as fixed mathematical quantities. In fact, just so far as Thomson substantializes electricity by giving it atomic structure, with invariable mass, the chemical atom becomes wavy and matter
