tric fields, and are neither refracted nor reflected. I would emphasize, however, their ability to discharge an electrometer, as well as to influence the photographic plate. Their peculiarities have been recently ascribed to the fact that they represented aperiodic impulses given to the luminiferous ether—which conveys no meaning to my mind, excepting that they can not be explained by the modulatory theory. The velocity of the canal rays has been determined, and the mass of their hypothetical particles measured by the amount of their deflection in magnetic fields of varying strength; both values approximate those found for the ordinary chemical atoms or molecules; in the case of the negative cathode rays, however, the velocities and mass correspond to those assumed for the electrons. I confess to a serious difficulty in harmonizing the notion of a corpuscular structure of the atoms with the explanation given by the same school for the need of high vacua for the production of cathode rays. It is said that the electrons must have a considerable free path in order that they may travel with undiminished velocity toward the anode: but if the atoms, instead of being compact elastic bodies, be mere nebulæ of electrons, the relation of whose sizes and interstices is comparable to that of the molecules in a normal gas, it follows that a free electron, hurled vehemently forward from the cathode, could pass quite through a number of atoms without collision with any of their constituent corpuscles; the free path of the electron is so enormous, on this hypothesis, that the order of its magnitude could not be materially affected by the degree of rarefaction of the gas customary in the Crookes tube.
We must recollect, however, that the hypothesis, first elaborated by Larmor, that the electrons are the primordial constituents of the atoms, does not, like that of Prout, simply extend the limits of the divisibility of matter. The electron is not to be considered as a small speck of matter at all, but as a permanent manifestation of energy concentrated on a minute portion of the luminiferous ether. This view and the explanation of many phenomena on such a basis has been acclaimed as the triumph of energetics, the final elimination of the conception of matter. An unbiased reading of J. J. Thomson's Yale lectures, however, will impress anybody that he decidedly materializes both energy and ether. Perhaps much of this materialization is purely symbolic, to bring his mathematical reasoning within the comprehension of his audience; but to me it seems that an electric charge which has quantity, mass, inertia, elasticity and expansibility, which obeys the laws of hydrostatics, and virtually has a surface beyond which it can only produce effects by the medium of mysterious lines of force, has a marvelous resemblance to the picture which the ordinary chemist's mind would form of material substance. His ether is not only that puzzling paradox, at once impalpable and inconceivably dense, rigid and frictionless, which we have accepted as the whole means of explaining the