1016] 



on The Genesis and Absorption of X-Rays 



'27 



directly proportional to the frequency of the rays, so that a measure- 

 ment of this energy specifies in a very convenient way the nature of 

 the Rontgen rays. 



The apparatus I used for carrying out the first method is repre- 

 sented in Fig. 1. A is the hot tungsten cathode; Gan anode made of 

 gauze ; T the target on which the rays strike. These rays pass through 

 the diaphragm D into the ionizing chamber I, which is a brass 

 cylinder about 40 centimetres long and 10 in diameter; this is filled 

 with parallel gauze discs, the adjacent ones of which are insulated 

 from each other, while alternate ones are connected together. One set 



Fig. 1. 



of discs is connected with one quadrant of a Dolezalck electrometer, 

 the other set to one of the poles of a battery of about 600 volts ; the 

 other pole of this battery is put to earth. If the quadrant of the 

 Dolezalck is originally put to earth, then on making the connection 

 the current flowing into the quadrant will measure the ionization in I, 

 and therefore the energy and the rays. To determine the character 

 of the rays, screens of metal foil are inserted between the diaphragm 

 and the ionizing chamber by means of the arrangement T. This is 

 a holder soldered on to the tube just behind the diaphragm, inside this 

 a metal plate pierced with a series of holes, one of which is empty 



