Remarks on Radioactivity. 485 



from activity. On removing the spiral from the liquid air, 

 the whole of the condensed emanation (allowing for the 

 decay of activity in the interval) is released at a fairly definite 

 temperature and appears again in the stream of gas. A more 

 detailed account of these investigations will shortly appear 

 in this journal. 



These results, in my opinion, conclusively show that the 

 emanations are gaseous in character, for it is very difficult 

 to explain such phenomena except on a material hypothesis. 



In addition, I have recently shown that it is extremely 

 probable that the greater proportion of the radiation from the 

 emanation is material in nature, and consists of heavy charged 

 bodies projected with great velocity, whose mass is of the 

 same order as that of the hydrogen atom. In view of these 

 results, which so strongly confirm the theory of the material 

 nature of the emanation, the alternative theory proposed by 

 M. P. Curie that the emanation consists of u centres de con- 

 densation d'energie situes entre les molecules du gaz et qui 

 peuvent etre entraines avec lui/' appears to me unnecessary. 



The interesting result, obtained by M. Curie, of the expo- 

 nential law of decay of the radium emanation under all 

 conditions, is only one of many others that have now been 

 accumulated. I quite agree with M. Curie that such results 

 cannot be satisfactorily explained on the laws of ordinary 

 chemical change, but the difficulty disappears on the view 

 already put forward by Mr. Soddy and myself (Phil. Mag. 

 Sept. and Nov. 1902) that the radioactivity of the elements 

 is a manifestation of sub-atomic chemical change, and that the 

 radiations accompany the change. 



There is no a priori reason to suppose that temperature 

 would affect the rate of atomic disintegration ; in fact the 

 general experience of chemistry in failing to transform the 

 elements is distinctly opposed to such a view. It is there- 

 fore not surprising that, if radioactivity is an accompaniment 

 of sub-atomic change, the process should be independent of 

 the ordinary chemical and physical agents at our disposal. 

 These points, and many others bearing on the same question, 

 are discussed in more detail in a joint paper with Mr. Soddy 

 now in the course of publication. 



I am, Gentlemen, 



McGill University, Yom ' s vei 7 trulv < 



Montreal, Feb. '28, 1903. E. RuTHERFOKD. 



Phil. Mag. S. 6. Vol. 5. No. 28. April L903. 2 K 



