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



carried by the deposit atoms and the mechanism of the 

 transfer in an electric field. Recently, Walmsley * published 

 the results of a series of experiments in which he eliminated 

 the disturbing causes existing in the work of previous in- 

 vestigators, such as presence of dust, moisture, &c, and 

 arrived at the following conclusions : — (1) The distribution 

 of the active deposit of actinium between the electrodes is 

 independent of the amount of the emanation, (2) with 

 suitable fields all of the deposit can be collected on the 

 cathode, (3) actinium A and B acquire their positive charge 

 in the process of their creation, (4) in an electric field 

 actinium A and B behave exactly like the positive gas ions 

 produced by their radiations ; they recombine in exactly the 

 same way (initial recombination being absent) ; and the 

 activity on the anode is due entirely to the diffusion of 

 uncharged deposit atoms formed by recombination in the 

 volume of the gas. 



The observation that the distribution of activity over a 

 wide range is independent of the amount of emanation and 

 that the activity on the anode is due to the diffusion of 

 neutral particles are in agreement with the results obtained 

 by Wellisch for the case of radium. On the other hand, 

 some of the above results are in direct contradiction to the 

 experimental facts established by Wellisch for the active 

 deposit of radium, which one would expect to hold in the 

 case of actinium also. 



The following investigation was undertaken with a view 

 of distinguishing between the two contradictory sets of 

 results and the corresponding theories, based on them, as to 

 the origin of the charges carried by the deposit particles,, 

 their mode of transfer and recombination in an electric 

 field, &c. The main objects of the experiments contained in 

 this paper may be briefly summarized as follows: — 



(1) Is it possible, under suitable conditions, to collect all 

 the active deposit of actinium ou the cathode ? 



(2) Is columnar as well as volume recombination present? 



(3) Does volume recombination between the positively 

 charged actinium deposit particles and the negative ions 

 take place at the same rate as the recombination between 

 positive and negative gas ions ? 



Before describing in detail the experimental procedure, it 

 is not out of place at this stage to draw attention to a funda- 



* H. P. Walmsley, Phil. Mag. vol. xxvi., Sept. 1913. 



