548 Mr. H. P. Walmsley on the Distribution of the 



employed in the last experiments, the deposit reaches the 

 electrode as radium A. The measurements of the distribu- 

 tion of the deposit are made, however, with the radia- 

 tion from radium C. We are, therefore, assuming that 

 the radium A decays in situ, although it is possible that 

 the anomalous behaviour of the deposit might be due to some 

 secondary effect during the course of these transformations. 

 Experiments were made with radium A alone. The elec- 

 trodes were exposed to the emanation for a short time 

 (2 mins.) in the apparatus, and the distribution of the deposit 

 found. The activity-voltage curve for short exposures is 

 quite similar to that obtained with long exposures. The 

 maximum value for the cathode activity was found to be 

 slightly less than in the case of long exposures, but little 

 weight is attached to this observation on account of the 

 difficulty of manipulation when the apparatus is used in this 

 way. The readings taken were not of a high order of 

 accuracy on this account, but no steps were taken to refine 

 the experimental methods, as I found that the main obser- 

 vation was supported by the work of Eckmann *. The 

 result indicates that no secondary effect after the deposition 

 of radium A on the electrodes is responsible for the observed 

 anode activity. 



Comparison of Radium with Actinium. 



If the anode activity, expressed as a percentage of the 

 cathode activity collected under the influence of a given 



Tig. 4. 











3-"""^'^ 









^ 



^^ 







-*r 



£ 



:,*«ii*i 









G- ^^ 



|^>- 







j^^" 





1 







a 6 



Mean time in thousandths of fi second 



field, is plotted against the mean time of passage of the posi- 

 tive ion from the gas to the electrode, in this field, we obtain 

 a straight line, fig. 4. The analogous curve obtained with 



* G. Eckmann, Jahr. der Had. tend Elcctronik, ix. 2, May 1912. 



