Precision-Measurements in the X-Ray Spectra. 677 



that of rock-salt is taken as log 2d = 3*7503541 -11 at 18° C. 

 In this work the unit of wave-lengths is 10~ n cm., according 

 to the proposal by Prof. Siegbahn *, and is here indicated 

 by X.U. The results of the examinations with calcite are 

 given in the following table, in which 



\ = wave-length (mean value). 

 i/ = frequence. 

 K=Rydberg's constant (logR = 5'0403650). 



Element. 

 29 Cu 



28 Ni 



27 Co ..' 



23 Va 



22 Ti 



21 Sc 



20 Oa 



19 K 



17 CI 



Table 



II. 





jine. 



A X.U. 



V 



E 



ft 

 ft 



1388-87 

 1382 



656-10 

 659-4 



ft 

 ft 



ft 



149669 

 1484-03 

 149811 



608-84 

 61403 

 608-25 



ft 

 ft 

 ft 



1617-15 

 1606 

 visible, not 



563-49 

 567-3 

 measured. 



ft 

 ft 

 ft 



227968 

 2265-37 



2285-26 



399-73 

 402-25 



398-74 



Pi 



ft 

 ft 



2508-74 

 2493-67 

 2515-06 



363-22 

 365-42 

 362-31 



ft. 

 ft 



2773-66 



2755 



328-52 

 330-7 



ft 

 ft 

 ft' 



3082-97 

 3067-40 

 3079-57 



295-57 

 297-07 

 295-90 



ft 

 ft' 



3446-38 

 344270 



264-40 

 264-68 



ft 



ft' 



4394-50 

 4391 



207-36 

 2075 



For the faint lines ft\ /3 2 , and ft" the accuracy is commonly 

 less, because they are measured relatively to the /Sx-line. 

 From his theory of X-ray spectra, A. Sommerfeld has con- 

 cluded that the /^-line must have a component f. Simul- 

 taneously the line ft' w T as observed in this laboratory in 

 some photograms {. I could follow this line right to Ti. 

 At Sc there was no component, but at the next element Ga 

 the other component ft" appeared, and was also discovered at 

 the following K and 01. The line ft 2 could be followed only 



* M. Siegbahn, Arkiuf. mat., astr. $ fijs. Bd. xiv. 1919. 

 t A. Sommerfeld, Sitz. Ber. d. Bayr. Akad. d. Wise. 1018. 

 X M. Siegbahn, toe. cit. 



Phil. Mag. S. 6. Vol. 41. No. 244. April 1921. 2 Y 



