56 POPULAR SCIENCE MONTHLY 



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 nega- 

 tive 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. Plaus- 

 ible, if not quite conclusive, reasoning connects the ionization hypoth- 

 esis 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 cur- 

 rent. This saturation current, it may be remarked, is used to char- 

 acterize 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 a, p and y 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 /? rays, the y variety being relatively few. a rays are electro-positive, 



