t*>42 Dr. Mamie Siegbahn on 



ri 



the crystals. This supposition is supported by the following 

 measurements of the doublet-distance between the ol x and 

 « 2 lines. 



Except these measurements, the Kc^-line was also 

 determined with another spectrograph especially built for 

 wave-lengths from about 0*5 A.U. up to 1 or 2 A.U., and 

 which was intended to bridge over the range of the above 

 short wave-length spectrograph and the vacuum spectro- 

 graph described in Part I. 



This new spectrograph gave also good results with shorter 

 waves, but the accuracy is not so high for such waves as 

 with the described spectrograph. In the following table 

 the measurements with the first spectrograph are denoted 

 J. 41-J. 48, W.2-W.7, and the results with the second 

 N.P. 32-N.P. 34. The three later spectrograms are taken 

 with a third specimen of calcite. As unit for the wave- 

 length is taken 10~ n cm., denoted by X.U. 



Table I. 

 The K aj-line of the Tungsten Spectrum. 



Date. 



Plate. 



Peflexion-angle 

 (Calcite). 



X . X.U 



12.12.18 



J. 41 



1° 



58' 



31"-5 



208-82 



12.12.18 



J. 42 



1 



58 



3L -3 



208-82 



13.12.18 



J. 43 



3 



57 



8 -6 (2 ord.) 



208-79 



17.12.18 



J. 48 



1 



58 



28 



208-72 



12. 3 19 



W.2 



1 



58 



33 



208-87 



13. 3.19 



W.3 



1 



58 



29 



208-75 



12. 3.19 



N.P. 32 



1° 



58' 



27"-4 



208-71 



13. 3.19 



N.P. 33 



I 



58 



29 -1 



208-76 



16. 3.19 



N.P. 34 



1 



58 



28 -1 



208-73 



4. 4.19 



W.4 



] c 



58' 



40" 



209-08 



5. 4.19 



W.5 



1 



58 



41 



209-10 



6. 4.19 



W.6 



1 



58 



33 



208-87 



8. 4.19 



W.7 



1 



58 40 

 Mean 



209-08 





208-85 



The a 2 -liue of the K-group was determined with reference 

 to the a^-line. On measuring the little distance between 

 these two lines on the spectrograms, the surprising result 

 came out that — in spite of invariable conditions — this 

 distance varied within rather wide limits. The reason 

 thereof may be sought in small irregularities in the crystal. 



