Jauncey — Effect of a Magnetic Field. 



147 



direct action of 7 -rays on air. In this experiment Kleeman 

 passed the 7-rays from radium through an aluminium plate and 

 then through a window of thin paper into an ionization 

 chamber, the distance between the aluminium plate and the 

 paper window being a few centimeters. On applying a mag- 

 netic Held to the space between the plate and the window 



Fig. 1. 



battery 



/\ 



4 



§■ 



-^ ground 



-^ electroscope 



Kleeman found that the ionization in the chamber was 

 decreased to about 55 per cent of its original value. The 

 magnetic field deflected the secondary /3-rays produced in the 

 aluminium so that these /3-rays no longer entered the ionization 

 chamber. 



It seems, therefore, that Kleeman's conclusion is invalid. 

 The secondary /3-rays which are scattered from the atoms of 

 the gas in the ionization chamber are not, according to Bragg,* 

 prevented from producing ionization by a magnetic field. 

 *" Studies," p. 166. 



