Manchester Memoirs, Vol. I Hi. (1908), No. \. 3 



position. No trace of helium was observed in the outer 

 tube over a period of eight days. Emanation was again 

 introduced, and after four days, the helium spectrum was 

 again observed. 



In these experiments, every precaution was taken to 

 prevent possible contamination of the apparatus with 

 helium. Freshly distilled mercury and fresh glass 

 apparatus was used. No trace of helium was observed 

 unless the emanation was introduced into the fine 

 capillary. 



This experiment affords a conclusive proof that the 

 o particle after losing its charge is an atom of helium. 

 Other evidence indicates that the positive charge on the a 

 particle is twice that carried by the hydrogen atom. 



