610 Mr. R, T. Beatty on Secondary 



a thickness #, the intensity would be I e~ Kx where I is the 

 initial intensity. Hence in this case the curve would be 

 exponential, and if plotted on semi-logarithmic paper would be 

 a straight line. With heterogeneous beams the curve would 

 be of the form 



y=A I e- x °* + A 1 I 1 e- x * x + . . . 



Fie?. 4. 



The curve for the two bulbs (fig. 4) shows clearly the hetero- 

 geneous nature of the radiations. The curve I did not become 

 a straight line within the limits of the experiment, while 

 Curve 11. shows a sensibly homogeneous radiation beyond 

 # = *20. Also the Curve II. is steeper than I., showing that 

 the corresponding radiations are more absorbable than those 

 in I. Hence the analysis of the radiations is in accordance 

 with our assumptions (1) and (2). 



Hitherto the plates placed at P and S had always been 

 •04 cm. thick, but now the thickness of these plates was varied 

 to get some idea of how P varied for different thicknesses of 

 plates. 



The results are as follows : — 





Table III. 





rickness of each of two 

 Al plates, one at P, 

 the other at S. 

 •01 cm. 



p. 



1-09 



Percent, of secondary 



cut off by corresponding 



plate in 1st column. 



16 



•04 cm. 



1-17 



37 



•265 cm. 



1-51 



69 



