produced in Air and Hydrogen by Rontgen Rays. 377 



may vary. It is evident from these experiments that when the 

 rays, which produce the ionization in the two gases, are kept 

 constant, the relative amount of ionization remains constant, but 

 that certain alterations in the rays produce an alteration in the 

 relative amount of ionization. Of course it has been known for 

 some time that the amount of ionization produced in a given 

 volume of any gas is dependent upon the type of rays used, but 

 it is evident from this investigation that an alteration in the type 

 of rays affects the ionization in these two gases in different 

 proportions. 



Experiments are at present being made, using a bulb in which 

 the pressure can be altered by means of an exhaust pump, to 

 determine what effect any alteration in the pressure of the gas 

 in the bulb has upon the ratio of the ionization for the two gases. 

 These experiments are as yet incomplete, but the indications are 

 that an alteration of the pressure in the bulb does affect this 

 ratio. They appear to show that the more highly exhausted the 

 bulb is, and consequently the harder the rays, the greater is 

 the ionization in hydrogen as compared with air. This question 

 is being more fully investigated, and it is hoped to have more 

 definite results shortly. 



In conclusion I would thank Professor Thomson for his 

 advice in connection with these experiments. 



VOL. XII. pt. v. 25 



