Page:Popular Science Monthly Volume 73.djvu/60

56 evanesces into the ghost-like form which energy has assumed in the chemical mind. If our scientific terms are, as it were, to receive the reciprocals of their present significance—progress may ultimately result, but we should enter into topsy-turvydom with our eyes open.

The electron theory possesses the merit of furnishing a working hypothesis upon which to coordinate the various electrical phenomena of vacuum tube and radio-active origin: chief among which is the increased conductivity of gases. Either direct current measurement or the more sensitive electrometer, determinative of the decrease of electro-static potential, indicates that gases begin to conduct electricity when affected by ultra-violet light, by cathode and X-rays, by radium, thorium, etc. Ingenious experiments have proved that portions of the gas are positively, others negatively, charged; that they behave as if ionized; the numbers, masses and charges of the hypothetical ions have been measured and found to agree with the assumption that the negative ions have the magnitude of the electrons, the positive ions that of the regular molecules, i. e., the negative ions are always very small and mobile, with the same value for all gases; the positive ions are, at least, 1,000 times as large, and vary for different gases. If the gas moves away from the locality of ionizing influence, its conductivity disappears gradually at a rate to suggest reunion of the ions. Plausible, if not quite conclusive, reasoning connects the ionization hypothesis with the novel phenomenon of the saturation constant; viz., the fact that the flow of electricity through a conducting gas increases proportionately to the voltage between the electrodes up to a maximum, when further increase of potential has practically no effect on the current. This saturation current, it may be remarked, is used to characterize radio-activity; it is admittedly a complex phenomenon, and I should be inclined to lay more stress upon the qualitative than the precise quantitative results obtained in a number of recent experiments.

Those who, like Armstrong, oppose the electrolytic dissociation hypothesis of Arrhenius, naturally attack the ionization hypothesis with still greater vehemence, and I believe that this will be the battleground of opposing theories for some time to come. As the phenomenon is distinctly a secondary reaction, from our point of view, we need not discuss it in its various aspects, beyond noting that even without detectable radio-active agencies the atmospheric air conducts electricity to a slight extent, varying with location, as well as with the hours of the day.

The radiations from the active chemical substances present a very complex aspect; besides light and heat, radium and its congeners send out $$\alpha, \beta$$ and $$\gamma$$ rays, respectively electro-positive, electro-negative and neutral when tested in electric and magnetic fields.

From radium a rays are sent out about four times as abundantly as $$\beta$$ rays, the $$\gamma$$ variety being relatively few. a rays are electro-positive,