376 Mr M c Glung, On the Relative Amount of Ionization 



in one would receive a charge opposite in sign to that received 

 by the corresponding plate in the other. If these charges were 

 equal in amount they would of course neutralize each other and 

 produce no effect on the electrometer. When a balance was once 

 obtained, by careful adjustment of the position of the different 

 portions of the apparatus, any alteration of the ratio of the ioniza- 

 tion in the one cylinder to that in the other could easily be 

 detected by the alteration in the balance. This method of 

 comparing the ionization in the two cases can be made a very 

 sensitive one. 



To compare the ionization produced in air with that produced 

 by the same source in an equal volume of hydrogen, the following 

 method was followed. The two cylinders, containing air at 

 atmospheric pressure which had been carefully dried, were care- 

 fully adjusted so that as good a balance as possible was obtained. 

 One of the cylinders was then exhausted and filled with hydrogen 

 at atmospheric pressure, the operation being repeated more than 

 once so as to insure that the hydrogen was as free from air as 

 possible. The ionization in hydrogen being quite different from 

 that in air the balance was now completely destroyed. To restore 

 the balance the cylinder containing air was partially exhausted 

 until the ionization in the air at the reduced pressure was 

 sufficient fo balance the ionization in the hydrogen. Now since 

 the amount of ionization in air is proportional to the pressure 

 of the air, therefore the amount of ionization in hydrogen at 

 atmospheric pressure can thus be compared with the amount in 

 an equal volume of air at the same pressure. 



Several experiments were made, using a Rontgen ray bulb 

 with an automatic vacuum regulator attached as the source of 

 the rays. The rays given out by this bulb remain pretty constant, 

 and exceedingly constant results were obtained with it. If Q A is 

 the amount of ionization produced in a given volume of air, and 

 Q H the amount in an equal volume of hydrogen at the same 

 pressure, then for this bulb the value obtained for the ratio 



Y^ was 0*11. Several other focus bulbs were tried, and they gave 



results which differed considerably from this value, and also 

 differed from one another. These were not automatic regulating 

 bulbs but simply the ordinary type of focus bulb, and they did 

 not give nearly so constant results as the automatic regulating 



one. One of these bulbs gave values for the ratio -^ varying 



between 0*060 and 0*084, and another one gave the two values 

 0052 and 0*056, while a third one gave the value 0*059. Different 

 bulbs usually give out different types of rays, and even the type 

 of rays given out by the same bulb under different conditions 



