772 Dr. A. N. Lucian on the Distribution of the 



for the distribution in the absence of an external electric 

 field (0 volts), so that diffusion alone was operative. It was 

 found that the deposits on the central rod and the case were 

 in the ratio of 1 to 6'6 approximately. This ratio is quite 

 different from the ratio of the areas of the central rod and 

 case, which was 1 to 37. It is evident that if we corrected 

 for diffusion on the supposition that the diffusion distribution 

 was proportional to the exposed areas, we should get higher 

 values for the cathode percentage. 



All the values given in the present paper refer to distribu- 

 tions for which the proper correction has been made. 



The curve for volts in fig. 2 would be expected to remain 

 horizontal for all amounts of the emanation employed. The 

 upward slope of the curve for very small amounts may be 

 due to residual electric fields as well as to molecular agitation 

 and initial diffusion from the recoil-column which are of no 

 effect for larger amounts. 



Some experiments of not a very high degree of precision 

 were tried with a negative potential applied to the case, the 

 central electrode being earthed. A typical set of equilibrium 

 values with added capacity for —600 volts on the case is as 

 follows : — 



Maximum activity on the central electrode ... = *08 '- 



sec. 



Maximum activity on the case = 10*7 „ 



Total activity = 10-78 „ 



Cathode percentage , . = 99*36 % 



Corrected for diffusion = 94 e 6 „ 



The corrected value for the cathode percentage is quite in 

 accordance with the values for + 600 volts when the central 

 electrode was made the cathode. 



It is now evident that if we followed Walmsley's pro- 

 cedure and obtained the distribution of the active deposit by 

 measuring the activity of the central rod, first as cathode 

 and then as anode, neglecting * the deposit on the case, we 

 should obtain for large potentials a cathode activity apparently 

 very nearly 100 per cent, of the total amount. 



The experiments with a negative applied potential show 

 further that the activity deposited on the anode is due 



* A close examination of the figures given by Walmsley in Table I. 

 (loc. cit.) seems to warrant the statement here made that he did neglect 

 consideration of the activity which diffused to the case (anode) at high 

 potentials. 



