Page:Popular Science Monthly Volume 73.djvu/57

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ought to exert some influence on an electron; if it accelerated its dextro-gyratory motion, it would retard its lævo-gyration, or vice versa. This is precisely what Zeeman found when he examined the emission-spectra of vapors that were placed in an electro-magnetic field; single lines are broken up into two or more finer lines, placed symmetrically with regard to the position of the original one. Righi has generalized the reasoning so that it covers practically every relation between the vibrating electron and the external magnetic strain to which it is subjected, and reaches two conclusions: First, the vibrating electron is electro-negative; second, the ratio e/m, i. e., electric charge over mass, is about 1,000 times as great as the ratio between the electric charge and mass of the hydrogen ion. Assuming, perhaps arbitrarily, that the electric charge is the same, the mass of the electron is about 1/1,000 that of the hydrogen ion; it can be no mere coincidence that Thomson, Kaufmann and others arrive at virtually the same figure for the mass of the corpuscles which carry the negative charges in ionized gases of whatever chemical constitution; in fact, everybody recognizes their identity.

To quote Righi, the neutral chemical atom (as distinguished from the ion) consists of a central mass of positive charge, around which revolve as satellites one or more electro-negative corpuscles, retained in their orbits by some centripetal force.

In connection with this definition, the following points seem to require emphasis: the number of electrons per atom are few, practically corresponding to the valency; this seems to be corroborated by recent experiments of Becquerel on the phosphorescence of uranium minerals at low temperatures, which likewise point out that light-emission is not always confined to the negative corpuscle, as Righi would have it. The total mass of the free electrons in an atom is not sufficient to affect the ratio between specific heats for constant pressure and constant volume of monatomic vapors, like mercury and cadmium; their velocity in their orbits does not approach that of light, and they have no high momentum retained by comparatively powerful internal attractions. These electrons can not be identical with the X-particles which are projected with terrific force from the uranium, radium and other atoms, according to Rutherford and his followers.

I need only touch briefly on the electric discharges in vacuum tubes: it is generally accepted that we distinguish Lenard or cathode rays, which are negative, and positive Goldstein or canal rays within the tube. They can be deflected by electric or magnetic fields, they produce mechanical and heating effects, cast visible shadows, etc., and they behave in general like streams of actual particles charged with electricity. When the cathode ray strikes an impenetrable obstacle, like glass, the X-rays are produced as a secondary effect: these do not behave as if conveyed by neutral particles; have vast penetrating power; contain no electric charge, as they are not influenced by magnetic or elec-