140 Mr. M. Ishino on the Scattering and 



The figures given in the 5th columns in the Tables, entitled 

 a crd" are simply the differences between the values given in 

 the 3rd and 4th columns. The values of cr d must be smaller 

 than the true value, since the absorption of the scattered 

 radiations in the materials and also the small amount of 

 scattering in the backward direction were neglected in 

 obtaining cr d . As previously mentioned, it is impossible, 

 at the present stage, to find the true value of the scattering 

 from the theoretical formula (6) or (6'), unless the law of 

 distribution of the scattered radiation is known. To give 

 an approximate correction, however, to the apparent value S 

 (Tables I. to III.), let us first assume that the absorption 

 correction for obliquity is omitted. Then we have 



S = ( ^e-^+^ae-^+W-^dx 



Hence we have 



a = lote-^+v)* ^ 



The figures given in the last columns in Tables IV. to VI., 

 entitled " cr K ," are the values calculated by formula (9). 

 It is noticeable that these values of g k are generally greater 

 than those obtained as the difference between the values of 

 fju 4- a and yu,, although the divergence is not very marked. 

 The values of cr K and also a d increase as the thickness of 

 the radiating plate decreases. This is what we should 

 expect, since the absorption due to obliquity has been 

 neglected. The values of a in the 5th and 6th columns 

 in Tables IV. to VI. are plotted in fig. 4, and the curves 

 connecting the values of <r K for each element continued to 

 cut the axis of cr. There seems to be little doubt that this 

 extrapolation for very thin radiating plates is justified. The 

 values of a corresponding to very thin plates were taken as 

 the true scattering coefficients. The results are as follows : — 







Table VII. 









0". 



JL. °f(JL) . **/(-) • 

 p p/Vp/ai a /U/ A i 



/a. 



It. 

 9 



Aluminium .. 



cm;' 1 

 . -105 



cm. 2 /gr. 



•0396 1-0 1-0 



cm.' 1 

 •0697 



cm. 2 /gr. 

 •0263 



Iron 



.. -290 



•0370 -93 -96 



•206 



•0262 



Lead 



.. -345 



•0304 -77 -82 



•460 



•0423 



*• .N = Moseley's atomic number of the element. 

 A = atomic weight of the element. 



