274 Mr Croii'ther, On the Scattering of ^-rays, etc. 



for various velocities of the jB-r^yQ. The first cohimn of the 

 table gives the velocity of the rays employed, as calculated from 

 their magnetic deflection ; the second column the corresponding 

 value of a, the coeflicient of scattering for air at normal temperature 

 and pressure. The third column gives the value of the product 

 V \la, where v is the velocity of the rays employed. It will be 

 seen that the coefficient of scattering of the rays varies rather 

 more rapidly than the inverse fourth power of their velocity. 

 This is probably due to the increase in the electrical mass of the 

 /S-corpuscles with increasing velocity. Prof. Sir J. J. Thomson * 

 has shewn that the coefficient of scattering is roughly propor- 

 tional to li'v^m-, where v is the velocity and m the mass of the 

 /S-corpuscle. Assuming the Lorentz formula for the change in 

 mass of an electron with change of velocity, we have 



where /3 is the ratio of the velocity of the corpuscle to the velocity 

 of light. Taking into account, therefore, this change of mass with 

 velocity we should have 



(1 — /3-) "*.■?;. Xja = constant. 



The last column of the table, which gives the values of this 

 quantity, shews how far this is the case. 



* See Conduction of Electricity through Gases, p. 377. 1906. 



