Homogeneous Corpuscular Radiation. 



351 



assumption in correcting for this effect, but it occurred to the 

 writer to test the matter by direct experiment. With the 

 apparatus previously employed values were obtained of the 

 total ionization due to the corpuscular radiation produced at 

 incidence and emergence respectively. The latter was found 

 to be roughly twice as great as the former. More elaborate 

 precautions would, however, be necessary to secure satis- 

 factory data. Experiments are now in progress with this end 

 in view. 



In many cases the ionization produced by the corpuscular 

 radiation from the aluminium window was small compared 

 with that produced by the corpuscular radiation from the 

 tertiary radiator, and the necessary correction was thus very 

 small. In all cases, however, two-thirds of the value of R 

 obtained when two aluminium surfaces were employed was 

 subtracted from the value of R when any other metal was 

 substituted for aluminium as the tertiary radiator to obtain 

 the value of R for the tertiary radiator alone. These cor- 

 rected values are tabulated below. 



Table V. 

 Values of Et. 



Tertiary 

 Radiators. 



Metals which serve as the source of Homogeneous 

 Secondary Rontgen Radiation. 



Fe. 



Co. 



Ni. 



Cu. 



z , 



As. 



Se. 



S, 



Mo. 



•2G4 

 •362 

 •458 

 •972 



Rho. 



Ag. 



Sn. 



Aluminium ... 



005 



•O0G 

 •013 



•008 

 •24;') 



•010 

 •2f>0 

 •01S 

 •148 



013 

 •255 

 059 



•178 



•028 

 272 

 •3G3 

 •333 



•038 

 •290 

 •377 

 •410 



071 

 •307 

 •387 

 •672 



•400 

 •500 

 •550 

 1-08 



•500 

 •590 

 •630 

 115 



•680 

 •700 

 •730 

 219 







Silver 



079 



•098 



•119 









The smaller values of R could not be determined with very 

 great accuracy, while in some cases it proved too small to be 

 measured at all, as, for instance, when the secondary radiation 

 from iron fell upon copper as the tertiary radiator. 



It was not to be expected that the sign of the potential of 

 the ionization-chamber I would influence the speed of the 

 corpuscules, since the field in which the corpuscules exist on 

 leaving the atom must be very much greater than that pro- 

 duced by the voltage employed in these experiments. 

 However, to test this point the outer case of the ionization- 

 chamber was first charged to +240 volts, and subsequently 



