[MCLENNAN- IONISATION TRACKS OF ALPHA R.\YS IN HYDROGEN 217 

 mercer] 



IV. Summary of Results. 



1. It has been shown that although alpha ray tracks in hydrogen 

 are of greater length than those in air they exhibit similar character- 

 istics to those obtained in air. 



2. It has been shown that alpha ray ionisation tracks can be 

 exhibited by the condensation of alcohol vapour equally as well as 

 with the condensation of water vapour. 



3. The photographs obtained confirm the observation of C. T. R. 

 Wilson and support the contention of Rutherford that apart from the 

 crooks at the ends of the alpha ray tracks the "scattering" is due to 

 single deflections through considerable angles. 



4. The experiments failed to bring out evidence in support of 

 ionisation by the nuclei of hydrogen atoms projected from the latter 

 when alpha particles collide with the atoms. 



5. The experiments go to show that when alpha particles are 

 projected through hydrogen exceedingly few collisions occur which 

 result in the ejection of a hydrogen nucleus. 



The Physical Laboratory, 



University of Toronto, 

 May 1st, 1915. 



