hy Homogeneous Rontgen Radiations. 



421 



Column 2 gives the coefficients of absorption by hydrogen. 



Column 3 is obtained by dividing the values of A, given in 

 Table I by the corresponding values in Table II. It will be 

 seen that the ratio increases as the cathode particles become more 

 jjenetrating. 



Column 4 gives the ratio of the total ionisation produced by 

 a given bundle of cathode particles in hydrogen to that produced 

 by the same bundle in air. The I'atio is unity luithin the limits of 

 experimental error. 



In Table III are added some data previously found for cathode 

 rays. It will be seen that the constants relating to the cathode 



Table III. 



particles due to the Sn radiation are very close to those found by 

 Lenard for corpuscles possessing a velocity due to a drop of potential 

 of 30,000 volts. 



Relation between the absorption of the cathode particles by air 

 and the absorption of the existing X -radiations by aluminium. 



This relation was found to be linear, and is shown in fig. 3. 

 The abscissae are taken from figures due to Barkla and Sadler*, 

 with the exception of that relating to Sn, for which radiation 



it was found by the author that - = 1*65, the absorber being 



aluminium. 



Relative ionisation in air and hydrogen due to homogeneous 

 X -radiations. 



The ionisation in hydrogen due to soft JT-radiations is so small 

 that the straight portion of the typical curve shown in fig. 2 was 

 almost horizontal. A separate set of experiments was made to 

 determine this ionisation accurately. The silver leaf was removed 

 from the chamber A and the plate electrode replaced by an 

 aluminium wire bent into a ring. The ionisation observed in the 

 chamber when filled with hydrogen and air respectively was then 

 determined. The results are given in Table IV. 



* loc. cit. 



