Deposit of Radium in an Electric Field. 445 



can be established in the vessel. When quantities of 

 emanation o£ the order of 1 millicurie were used, the amount 



Fig. 6. 



of active matter carried to the plate by the current of air 

 was found to be 4 or 5 times as large as that deposited on 

 the plate by diffusion. 



On the Gas Activity. 



10. It has been shown in sec. 4 that uncharged radioactive 

 atoms readily attach themselves to dust particles and tend 

 to form large aggregates with a very slow rate of diffusion. 

 This may be observed in a gas containing emanation, when 

 no electric field is applied to carry the newly formed recoil 

 atoms to the electrodes, in which case a considerable fraction 



