710 Velocities of a Particles from Thorium Active Deposit. 



(3) A direct comparison has been made between the 

 velocities of the a-particles expelled from thorium active 

 deposit and those expelled from radium C. Taking the 

 velocity of the a-particles of S'6 cm. range (from thorium C 2 ) 

 -as unity, we have 



a-particle. 

 Source. | Bange. 



EaC 



ThC x 



6'94 cm. 

 4-8 cm. 



Observed 



velocity. 



1 

 0-932 



0-832 



Velocity calculated from 



Geiger's relation 



(i; 3 =£R). 



1 

 0-932 

 0-826 



(4) Using the standard value 1*922 x 10 9 cm/sec. as the 

 velocity of the a-particles from radium C, it is found 



(a) Velocity of a-particles from Th C 2 = 2*060 x 10 9 cm./sec. 



(b) Velocity of a-particles from Th C l= = 1*714 x 10 9 cm./sec. 



(5) The relative intensities of the two a-ray lines shown 

 in the photographs are discussed with regard to the question 

 of the relative numbers of ^-particles expelled with ranges 

 of 8*6 cm. and 4*8 cm. respectively. 



(6) No evidence has been obtained as indicating a difference 

 of mass of the two sets of a-particles. 



In conclusion, I should like to express my thanks to 

 Prof. L. R. Wilberforce for his kind interest and for pro- 

 viding me with the apparatus necessary for these experiments. 

 I must take this opportunity also to express my indebtedness 

 and thanks to Prof. Sir E. Rutherford, F.R.S., for suggesting 

 the second part of this research and for supplying me with 

 the radium emanation used in the later experiments. 



Holt Physics Laboratories, 

 University of Liverpool. 

 July 1915. 



