Deposit of Radium in an Electric Field. 



431 



show that the radioactive atoms entering the tube t are 

 realty uncharged. Thus, a strong stream of air maintained 

 between the plates C and D carries away completely the 

 active matter even when large potential differences are 

 applied to the plates. Further, the activity received by the 

 plate D does not depend upon the sign or the strength of 

 the electric field in the condenser CD. Also, if the plate D 

 be replaced by another provided with a central aperture, the 

 recoil atoms are carried by the wind through this aperture, 

 and the plate remains inactive in spite o£ the electric field 

 established in the condenser CD. 



3. In order to investigate the distribution in an electric 

 field of uncharged radioactive recoil atoms by applying the 

 principle described in the previous section, the following 

 apparatus has been constructed. Two square metal plates A 



Fi>. 2. 



and B (fig. 2), provided in the centre with square apertures 

 aa and 66, are insulated from each other by four rectangular 

 pieces of glass #, forming thus a closed vessel, which may be 



