4 CATHODE RAYS LOSS OF ENERGY, ETC. 



R.S. TAS. 



By eliminatini^- v from (vi) and (i) we get the relation 



n =-j~ (vn) 



km 



Thus from (vii) we may calculate TF, the energy of an ion, 

 or by combinino- (vii) iwith (v) we get tbe ratio ^^, i.e., the 

 energy lost by the ray to the energy spent in ionisation. 



T7 'J J.1 '^"tn^ / •••X 



Evidently IT = 8^« (""> 



In order to calculate the value of n we refer to a paper by 

 Crowther (Prnc. Hoy. Soc, vol. 84, p. '226), in which he 

 shows that ior the five elements C, Al, Cu, Ag, Pt, whicli 

 have atomic weights varying from 12 to 195, the number of 

 electrons in the atom is three times the atomic weight to 

 within a iew per cent. Assuming that this holds also for 

 the atoms of and N, we find that the number of electrons 

 per c.c. of air at 760 m.m. is v. = '2''d x l()*i. 

 Putting this value in (ix) we get 



^. = 5-5 (approx.) 



'Thus the energy s^penf in ionisation is one- fifth o' the n'inde 

 energy spent hi/ the ray. 



I am grateful to Professor Kerr Grant, of the University 

 •of Adelaide, for valuable suggestions in connection with this 

 paper. 



The University of Tasmania, 

 29th March, 1913. 



