200 Dr. Tycho B:son Auren on 



I. and II. being somewhat lower than those calculated may 

 be due to the fact that, with a thinner filter, besides waves 

 o£ shorter wave-lengths there have occurred rays of an 

 appreciable intensity of greater wave-length than \ = 0*37. 

 As the found values of ~ic /ri for the lighter elements have 

 been calculated by aid of the observed values of q for the 

 radiation referred to, no error can have originated in 

 the fact that the wave-length range has partly extended 

 beyond the limit just mentioned. From what is said 

 it appears, however, that the formula /c = C + A\ 6 is not 

 applicable on different sides of the limit unless C gets the 

 value corresponding to respective wave-length, and more 

 especially this holds regarding the lighter elements, in 

 which C plays a proportionally great part. 



In case we assume that in Al 6, instead of 5, electrons 

 are arranged as outer electrons, and accordingly ^ 1/H - q 



is calculated by the formula fr-zrz — ~, the values stated 

 J 0-91 + 6^' 



in the last column of Table XIII. will be obtained. The 

 agreement of the thus calculated and the observed values 

 is for the greater wave-lengths about as good as in the case 

 where the calculation is made after the formula (14); but, on 

 the other hand, the agreement for the shorter wave-lengths 

 is less good and shows a clear divergence. 



If we believe that the number of electrons is the same as- 

 the atomic number, then with decreasing wave-length the 



limiting value for k .,,„„. must be -=-x- But Barkla and 

 ai/±i 2 u iq 



White have shown that — for Al, in case of shorter waves^ 



P 

 tends towards being less than for H 2 0, and, in case of suffi- 

 ciently short waves *.,,„- q must be apt to be less than 1. 



If, according to the formula (15), we merely suppose 5 outer 

 electrons in Al and 6 in H 2 0, then k A] /h q will get the 



value of 1 when q has reached the value of 3*96 ; and 

 as this value still increases with decreasing wave-length, 

 Kj£ , H q will be <1. Thus we have reasons for believing 



that the number of outer electrons must be less in Al than 

 in H 2 0, and the observations (Table XIII.) show that the 

 relation of these electron numbers may very closely be 

 regarded as 5:6. 



From the known values of q the mass scattering co- 

 efficient I-) may be calculated. According to what was 



