212 Pays of Positive Electricity. 



heating effect made by various observers. The number o£ 

 direct measurements on the distribution of energy between 

 the a and ft particles is, however, only small, and these are 

 sometimes contradictory; so that the available evidence is 

 mainly indirect, and rests on the observed parallelism between 

 heating effect and a-activity. So far as it goes, it is in favour 

 of the second class of theories. The question is, however, of 

 such fundamental importance that measurements specially 

 directed towards its solution are desirable. 



If further experiments confirm Rutherford's conclusion, 

 we shall be face to face with the problem of constructing a 

 system of positive and negative charges, hoth of which are in 

 rapid orbital motion, and which shall be sufficiently stable 

 and permanent to exist for long periods, and yet capable, as 

 it were, of occasional lapses from stability, producing a sudden 

 explosion with expulsion of positive and negative charges. 

 Physical Institute, Bonn, April 29. 



XIV. On Rays of Positive Electricity. By W. WiEN *. 



PROF. J. J. THOMSON has published in a previous 

 number of the Phil. Mag. (May 1907) an interesting 

 paper on the rays of positive electricity. 



May I make some short remarks in reference to the 

 publication of Prof. Thomson. 



(1) The existence of negative ions, which are deflected in 

 the opposite sense to the positive in a magnetic field and have 



£ 



a small value of , was observed by myself some years ago 



and published in a footnote (Ann. der Phys. viii. p. 262, 1902). 

 I found this negative radiation very feeble. In another paper 

 {Ann. d. Phys. xiii. p. 669, 1904) I have published expe- 

 riments on the electric charge of the positive rays, which are 

 deflected in a magnetic field. But I found no negative charge 

 in a field of opposite direction (see p. 674 of the paper). 

 This shows that the negative ions are only a small part of the 

 positive. 



(2) The possibility, that the variable deflexion of the 

 Kanalstrahlen in a magnetic field is due to the fact that 

 the ions lose or receive their charge at different points of 

 their paths, is discussed in the latter paper (p. 669 and p. 677), 

 besides the other hypothesis that we have to assume ions of 

 large mass. I have no preference for the one or the other 

 assumption, but I do not see that the question is definitely 

 decided . 



* Communicated bv the Author. 



