﻿808 Emission of Electrons by X-Rays. 



capable of ejecting a large number of slow electrons from 

 the atoms with which it comes into collision. Exactly the 

 same process should occur during the passage of electrons 

 through a metal. In this case the number which will 

 succeed in escaping will be relatively small owing to their 

 low speed and consequent rapid absorption in the metal. 

 The fact that quite a small accelerating field considerably 

 increases the number of these electrons, shows that many of 

 them are unable to escape unless their energy is increased 

 by outside fields. 



(10) Summary of Results. 



(a) The electron emission from various metals and a few 

 salts under the influence of X-rays has been measured, and 

 an attempt has been made to deduce from these measurements 

 the relation between the number of electrons emitted per 

 atom per unit intensity per unit time and the atomic number 

 or atomic weight of the substance from which they are 

 liberated. 



(b) It has been found that under these experimental 

 conditions the special electron emission associated with the 

 characteristic X- radiations of the substances bombarded is in 

 these experiments only a very small fraction of the total 

 electron emission. 



(c). These experiments have yielded no evidence of anv 

 selective emission in the direction of the electric vector in 

 the X-ray beam. 



(d) It has been shown that the electron emission per 

 unit intensity diminishes as the penetrating power of the 

 radiation is increased. 



(e) The properties of the low-speed - electrons which 

 accompany the high-speed emission have been investigated, 

 and this emission has been ascribed to a secondary effect due 

 to the action of the fast electrons. 



This work was carried out at the Cavendish Laboratory, 

 Cambridge, and the author has great pleasure in acknow- 

 ledging the continual kindness and many helpful suggestions 

 he lias received during its progress from Prof. Sir Ernest 

 Rutherford, F.R.S. 



