250 Taylor- Ionization of Different Oases by the 



curves obtained in different gases that the present experiments 

 were begun. 



Continuation of Experiments. 



The apparatus used was the same as had been. used in the 

 previous experiments.* The sheet iron case, enclosing the 

 apparatus proper, was replaced by a solid iron case which could 

 be readily exhausted. Polonium was used as the source of 

 rays and was placed in a brass cylinder of such dimensions 

 that the rays emerging from the cylinder fell well within the 

 limits of the ionization chamber for all available distances of 

 the source of rays from the ionization chamber. 



In the determination of the ionization curve in any gas, the 

 vessel enclosing the apparatus was first evacuated and then the 

 gas admitted very slowly till the pressure it exerted was such 

 that the range of the alpha particles was exactly 11*1 centi- 



Fig. 1. 



Fig. 1. The ordinates are the deflections in millimeters of the electrome- 

 ter needle per second. The abscissas are the distances in centimeters of the 

 polonium from the ionization chamber. Curves I, II, and III were obtained 

 when the maximum range of the alpha particle was exactly 11 - 1 centime- 

 ters in hydrogen, air, and methyl iodide, respectively. 



meters, which was the maximum range available with the 

 apparatus. The Bragg ionization curve was then obtained in 

 the usual manner by observing the deflection of the needle of 

 the Dolezalek electrometer in scale divisions per second for 



* Loc. cit. 



