436 Mr. S. Ratner on the Distribution of the Active 



increases when large quantities of emanation are used could 

 be easily explained from this point o£ view. 



Various experiments have been undertaken in this di- 

 rection. The experiments to be described in this chapter are 

 based on the principle given above. A strong source o£ 

 ionization is introduced into the exposing vessel in order to 

 increase the rate of recombination of the recoil atoms and 

 to produce an electric wind in a desired direction. As source 

 of ionization a disk was used which had been exposed for a 

 long time to a large quantity (from 10 to 250 millicuries) of 

 emanation. The quantities of emanation introduced into the 

 vessel in which the experiments were made varied from *01 

 to 1 millicurie, so that the ionization and consequently the 

 electric wind due to the emanation were vanishingly small 

 compared with those produced by the additional source of 

 ionization introduced into the vessel. 



The exposing vessel used consisted of a glass tube A (fig. 3), 

 3*5 cm. in diameter and 12 cm. long, provided with two 

 rubber stoppers through which the electrodes, two brass 

 plates P, are introduced into the vessel. By means of a 



Fig. 3. 



water-pump the vessel is evacuated, and the emanation kept 

 in a large bottle is allowed to enter the vessel through a tube 

 filled with cotton-wool in order to remove the gas activity. 

 One of the electrodes is charged to a desired potential by 

 means of a battery of small cells, while the other one is 

 earthed; the distance between them varied from 4 to 6 cm. 

 The plates were usually exposed to the emanation for 10 

 minutes, and their activities measured about 20 minutes after 

 their removal from the vessel. Since the volume of the 

 vessel is small compared with that of the bottle containing 

 the emanation, the quantity of emanation introduced into the 



