Produced by Rontgen Rays. 



43 



The gases were dried by passing slowly through a tube con- 

 taining phosphorus pentoxide and the vapors were bubbled 

 through sulphuric acid when necessary and were always passed 

 through a calcium chloride drying tube. 



Description of Apparatus. 



The general arrangement of apparatus is shown in flg. 1. 

 The ionization chamber K is lined with aluminium and pro- 

 vided with two parallel plate electrodes A and B of aluminium, 



Fig. 1. 



the latter being surrounded by a guard ring C which is con- 

 nected with the walls of the chamber. The insulated electrode 

 B may be connected with an electrometer by means of a key 

 D. The beam of X-rays is restricted by adjustable lead 

 screens MM' and NN' so that it does not fall on the electrodes. 

 A pendulum E- is used for automatically giving the flash of 

 X-rays by opening the key S and, after a definite interval of 

 time, applying a potential to the electrode A by opening the 

 switch F, which may be placed at any position along the path 

 of the pendulum. 



In order to obtain X-ray flashes of sufficient intensity it was 

 sometimes necessary to interrupt a current of 25 amperes at 

 the key S. Although a large adjustable condenser was used 

 for suppressing the spark, considerable difficulty was expe- 

 rienced at first in getting uniform conditions in the induction 



