﻿the Active Deposit of Radium in an Electric Field. 729 



neutral although unstable condition, and a certain number of 

 them are afterwards resolved into ions, probably as a result 

 of collision with the ions already established in the columns. 



These neutrons are in all probability formed most 

 numerously during the early part of the range of the 

 a particle, when it is moving with its largest velocity. The 

 approximately horizontal parts of the ionization curves such 

 as are obtained at low pressures, or when the a particle 

 moves perpendicularly to the lines of electric force, would 

 therefore only represent saturation in the sense that all the 

 free ions have been brought over to the electrodes because 

 in these cases it is unlikely that an appreciable number of 

 neutrons would be resolved into ions. 



As far as the active deposit particles are concerned we 

 may regard them as neutral restatoms which have been 

 exposed to the action of the a particle at the moment of dis- 

 integration of the emanation atom ; we would thus expect 

 them to be for the most part radioactive neutrons which have 

 in general to be subjected to further influence before acquiring 

 a positive charge. 



Experiments which are now in progress suggest also that 

 the shape of the Bragg-Kleeman ionization curve can be 

 accounted for by the formation of neutrons and ions in 

 different proportions along the entire range of the a particle. 



8. Summary. 



(1) The distribution in an electric field of the activity 

 resulting from a long exposure to the emanation of radium 

 has been determined for various conditions of pressure, 

 potential, <fcc. 



(2) There appear to be no negatively charged carriers, all 

 the so-called anode activity being due to the diffusion of 

 uncharged carriers. 



(3) The effect on the distribution obtained by causing 

 Rontgen rays to pass through the gas during the exposure 

 has been investigated ; this effect was appreciable only when 

 the activity and ionization were far from saturation. 



(4) The difficulty of obtaining saturation both for the 

 cathode activity and for the a ray ionization currents has 

 been explained as being due to the formation by the a particle 

 of neutrons, some of which are subsequently resolved into 

 ions, probably by collision with ions already established in 

 the columns. 



