Magnetic Change of Resistance at Various Temperatures. 11 

 Table X. 







Ionization current 



Ionization current 



I.x 100 







in A. 

 Ia. 



inB. 

 Ib. 



Radium emanation. 

 Xo diffusion-vessel. 



I 



100 



96-2 



100 



Radium emanation. 

 Diffusion experiment. 



1 



100 



521 



542 



Thoriuna emanation. 

 Diffusion experiment 



1 



100 



421 



43-7 



Thorium emanation. 

 No diffusion-vessel. 





100 



81-2 



84-4 



From Table X. the following values can at once be 

 obtained : — 



#1 = 100, y 2 ==54-2, 



z =100, z=S§'^ e 2 =43'7, s 2 '=84'4. 



Substituting in equation (7) 

 , 100 



loo- 



X _ °54-2 ^-266 



V" 



, 88-8 , 88-8 -286 

 l0 »Wl- } °Z*¥I 



■931. 



It thus appears that the molecular weight of thorium 

 emanation does not differ much from that of radium, though 

 the former would seem to be somewhat smaller. 



1 am indebted to Professor J. J. Thomson for many sug- 

 gestions, and I would thank him for the interest which he 

 has taken in the progress of this investigation, which was 

 carried out at the Cavendish Laboratory. 



V. On the Magnetic. Change of Resistance in Iron, Nickel, 



and Nickel-Steel at Various Temperatures. By W. E. 



Williams. B.Sc, Research Fell no of the University of 



Wales*. 

 TI^HE influence of temperature on the change of resistance 

 X with magnetization in iron and nickel has been studied 

 previously by Dr. Knott and also by the present writer. 



Dr. Knott t has measured the change of resistance in 

 nickel at various temperatures up to -100° C. for fields from 



* Communicated by Professor A. Gray, F.R.S. 

 t Trans. R. S. Edin. xli. 1904, p. 39. ' 



