550 Mr. H. P. Walinsley on the Distribution of the 



velocity is such that they are entirely uninfluenced by elec- 

 tric fields of the order of magnitude of those employed in 

 these experiments. He advances the hypothesis that recom- 

 bination between the recoiling atoms and negatively charged 

 ions occurs during the recoil, and hence, when the active 

 deposit has attained the mean velocity of the surrounding- 

 gas molecules, a definite fraction are uncharged, and conse- 

 quently distribute themselves over the exposed solid surfaces 

 irrespective of their relative potentials. This would account 

 for a permanent anode activity uninfluenced by electric 

 fields. The suggestion is rather discounted, however, by the 

 observations on actinium active deposit. The masses of the 

 recoiling atoms in the two cases (radium A and actinium A) 

 are of the same order of magnitude, whilst the violence of 

 the atomic explosion, which determines their range and the 

 ionization produced by them, as measured by the ranges of 

 the ejected a particles, is greater in the case of actinium than 

 in that of radium. Hence we might expect a constant anode 

 activity in the disintegration of actinium emanation in an 

 electric field, which, however, is not supported by experiment. 



A more satisfactory explanation perhaps can be brought 

 forward on the hypothesis, which, however, is not free from 

 adverse criticism, that a partition of radium A occurs between 

 the space and the bounding surfaces of any enclosure con- 

 taining it. Suppose that at the moment of its formation 

 every atom of radium A is positively charged. If a suffi- 

 ciently intense field is applied, these are all dragged on to 

 the cathode after they have attained the average velocity of 

 the gas molecules within the enclosure. On reaching the 

 cathode they are probably neutralized by combination with 

 free electrons, after which a partition is set up which creates 

 a uniform distribution of uncharged radium A throughout 

 the gas. This impinges against the anode, and some of 

 it collects there until equilibrium is again attained. Thus 

 we have the major part of the radium A remaining on the 

 cathode, some existing in the gas in an electrically neutral 

 state and a little remaining on the anode. Superposed upon 

 this distribution is that due to the radium A recoil atoms 

 which have recombined with negative ions before reaching 

 the cathode. These partition themselves in a definite way 

 between the metal surfaces and the space between them by 

 diffusion, and of course, there is collected by all surfaces a 

 small amount of active matter which is directly projected on 

 to them by recoil. 



In practice the transference of radium A from the cathode 

 to the anode by a process of partition is modified bv the 



