138 Mr. M. Ishino on the Scattering and 



The difference between the ionization currents with and 

 without the radiating plate at R 3 behind the electroscope 

 (fig. 2), when corrected for the absorption of the primary 

 beam by the walls of the electroscope, should give the 



Fig. 3. 



14 



12 



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iC 



amount of scattering in the backward direction. A number 

 of such observations have been made. It was found, how- 

 ever, that the difference in the readings was too small to be 

 determined with any great accuracy by direct electro- 

 scopic method, amounting generally to only a few per 

 cent. Accordingly, only the mean value of the ratios of 

 the scattering in the backward to that in the forward 

 direction was estimated, and found on an average to be 

 15 per cent. Madsen * estimated the ratio to be about 

 18 per cent. 



By the formula (7) the value of yu- + cr was calculated from 

 the figures in the 3rd and 4th columns in the preceding 

 tables ; similarly, by the formula (8), the value of /jl from 

 the figures in the 3rd and 5th columns. The values so 

 obtained are given in Tables IV. to VI. 



* Madsen, Phil. Mag. xvii. p. 423 (1909). 



