RICHARDS. SIGNIFICANCE OF CHANGING ATOMIC VOLUME. 15 



explained by the aid of the ingenious hypothesis of "electrons," as 

 amplified by J. J. Thomson and his students in the brilliant experimental 

 researches published in the recent volumes of the Philosophical Magazine. 

 This daring hypothesis must not be accepted without reservation, how- 

 ever. Some physical objections to it have been suggested by Ernest 

 Merritt in his interesting address to the American Association for the 

 Advancement of Science ; * and other objections arise when one tries 

 with its aid to unravel the tangle of influences involved in purely 

 chemical action. The rejected alternative of imagining the atom as 

 indivisible, but as capable of receiving widely varying electric charges 

 under widely different conditions, has some advantages which the opposite 

 hypothesis does not possess. The subject is much too large for discus- 

 sion here, however. One phase of it, which bears directly upon the sub- 

 ject of the present paper, may receive brief notice. 



The results of Thomson, Townsend, Zeleny f and others seem to indi- 

 cate that the bearer of the negative electricity not only carries the high 

 charge referred to above, but that it is very small, while the bearer of the 

 positive electricity is very large. May it not be the atom itself which thus 

 expands and contracts ? This agrees with the verdict of the results of 

 atomic compression given above. Change of atomic volume seems to be 

 associated with electric stress. This assignment of electric expansibility 

 to the atomic sphere of influence might explain other phenomena con- 

 cerning the behavior of electrified gases, for example, the increase of 

 pressure which is observed when a gas is highly charged.^ Again, the 

 great conductivity of a gas with adequate potential and quantity of 

 electrical discharge § seems to indicate that then the situation must 

 resemble that in a metal, where the spheres of stress fill the whole 

 volume occupied by the substance. The temperature must be so high 

 under these circumstances that the gas is probably in a condition of 

 thermal dissociation. Hence one is inclined to refer the great conduc- 

 tivity to the electrical susceptibility of evenly compressed or undistorted 

 atoms. The fact that pure metals conduct electricity better than alloys or 

 compounds seems to support this conclusion. The permeability of solids 

 to cathode rays might be explained by supposing that the smallest particles 

 of both solid and gas are much contracted by the negative charge. 



* Proc. Am. As. Adv. Soc, 1900, p. 49. 



t Phil. Mag. [5] 46, 120, (1898). See also Am. Chem. Journ., 25, 340 (1901), 

 for a resume' of this work. 



X De la Rue and Miiller, Phil. Trans., 1880, SG. 



§ Trowbridge and Richards, Phil. Mag. [5] 43, 349 (1897). 



