530 Miss Jadwiga Szmidt on Distribution oj Energy in 



investigators*. There is no close agreement between the nume- 

 rical values obtained by the different observers, apparently 

 owing to the difference in experimental arrangement. The 

 above values for 7 rays are of the same order of magnitude 

 as for X rays with corresponding penetrating power, and 

 compare best with Owen's results. 



For the 8 types of X rays examined (from yu, = 241 cm. ~ : Al 

 up to yu,= 13 cm. -1 ), all belonging to the " K " series, Owen 

 found the absorption in C0 2 and in S0 2 proportional to the 

 absorption in air, the ratio of the absorption coefficients 

 varying from 1* 6-1*8 in one case and from 9 , 1-10 , 6 in the 

 other. For the soft 7 rays from radium D this ratio is equal 

 to 1*68 and 9*97 respectively. 



It had been noted by Owen that there is a simple connexion 

 between the absorbability of X rays in a gas and the atomic 

 weight of the radiator emitting this particular type of radia- 

 tion: the logarithms of /njp (mass absorption coefficient) 

 plotted against the logarithms of the atomic weight of the 

 radiators were found to lie on straight lines parallel to each 

 other in the case of air, C0 2 and S0 2 . From the curves 

 the values of the atomic weight corresponding to the values 

 of /jl/p given in Table I. were found to be 80*7, 809, and 

 79' 7 respectively. Whiddington f was the first to point out 

 an experimental connexion between the atomic weights of 

 " K " and " L " radiators emitting the same type of charac- 

 teristic radiation. Using this connexion in the special form 

 given by Chapman J, 



W K =i(W L -48), 



we obtain as mean value Wl = 208*7; or, in other words, the 

 " L " characteristic radiation from an element of atomic 

 weight 209 should correspond to the " K " characteristic 

 radiation of the element with atomic weight 81. The atomic 

 weight of radium D being 210, this seems to confirm the view 

 that these 7 rays are the characteristic " L " rays set up in the 

 disintegration of the atoms. 



It is interesting to compare the absorption in a H 2 S molecule 

 with that of a S0 2 molecule, where the oxygen is substituted 

 for hydrogen. If, again, we assume that the absorption by 

 the hydrogen atoms is negligibly small and that the absorption 

 in oxygen is 1*4 times thnt in air (as found by Gowdy for 

 X rays), that is 0*0057 at 0°, then we obtain yu, in S0 2 as the 



* Owen, Proc. Roy. Soc. A, lxxxvi. p. 426 (1912). Gowdy, loc. tit. 

 Barkla and Collier, Phil. Mag. xxiii. p. 987 (1912). 

 t Whiddington, Nature, 30 November, 1911. 

 % Chapman, Proc. Roy. Soc. A. lxxxvi. p. 439 (1912). 



