136 



BELL SYSTEM TECHNICAL JOURNAL 



been explained (page 129). Only tentative theories of these have 

 been made, and it would be of little use to expound them here.^^ 

 Notice then in Fig. 9 the beautiful long sloping line adjoining the 

 plateau, and implying a continuous distribution over a wide interval 

 of ranges extending up to 7.8 cm. The numerous shorter tracks of 

 Fig. 15 are due to particles belonging to this continuum. Observe 

 last the integral distribution-in-range curve for the fragments from 



Fig. 14 — Tracks of paired fragments, He nuclei believed to result from impact of a 

 proton on a Li^ nucleus and from impact of a deuton on a Li^ nucleus. (Dee and 

 Walton ; Proceedings of the Royal Society) 



boron bombarded by protons. Fig. 11; notice that it displays no 

 definite step, but consists of a single sloping arc implying a continuum 

 extending to an upper limit, which on a magnified curve is found to be 

 at 4.7 cm. 



It is now suggested that in both of these two last cases we have 

 processes in which there are not two, but three final fragments: 



iH' + sW + 7^0 = 22He^ + o«' + T,, 



(5) 

 (6) 



22 Dee has just announced (Nature, 132, 818-819; Nov. 25, 1933) that these short- 

 range fragments are frequently paired. In doing the experiment he admitted the 

 primary protons into the expansion-chamber through a thin mica window, the 

 target being within. 



