[eve] 



PRIMARY AND SECONDARY GAMMA RAYS 



41 



Using the electroscope previously described, fig. 1, the mean 

 results obtained, for different screens as stated, and in the manner just 

 described, are given in Table III. 



Table III. 



^ /\TQMIC \A/EIGHT' 



Fig. 3. 



The corresponding 3 curves are shown in figure 3. The changes 

 in the relative positions of carbon and lead according to the nature 

 and thickness of the screens employed are very striking, and at first 

 sight suggest selective absorption, and a number of experiments 

 were made to examine this pecuharity. 



