Alpha Particles from, Polonium. 251 



various distances of the source of rays from the ionization 

 chamber. In this manner, the Bragg ionization curves were 

 obtained in the gases and vapors given in Table I. The curves 



Fig. 2. 



Fig. 2. 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 centimeters 

 in methane, ethyl chloride, and carbon disulphide, respectively. 



in figures 1 and 2 and the dotted ones in figure 3 represent the 

 ionization curves obtained in the above manner in the gases 

 as indicated below the figures, respectively. The dotted por- 

 tion of each curve in figures 1 and 2 is assumed to be the form 

 it would take were it possible to move the polonium entirely 

 up to the ionization chamber. At any rate, such assumed por- 

 tions of the curves can differ but little from the actual curves. 

 It is to be npted, that the ionization curves shown in figures 1 

 and 2 are plotted differently from the regular Bragg ioni- 

 zation curve in that the values of ionization are taken as ordi- 

 nates and distances of the source of rays from the chamber as 

 abscissas, instead of vice versa as is usually done. 



Although the curves in figures 1, 2, and 3 represent some 

 differences from one another in regard to the relative amounts 

 of ionization for corresponding distances of the source of rays 

 from the ionization chamber, all of them are of the same general 

 form. From a re-determination of the velocity of the alpha 

 particle at different points in its path, and the assumption that 



