Precision-Measurements in the X-Ray Spectra. 675- 



covered by the rotating fluid. The variation of pressure 

 with height above the ground indicated in the various cases 

 may also be capable of observation, although this would no 

 doubt prove a much more difficult matter. The solutions 

 obtained above deal only with a very special atmospheric 

 motion in which the angular velocity of the rotating fluid is 

 uniform throughout the whole mass of fluid and horizontal 

 temperature gradients are neglected. This may also prove 

 to be not in accordance with actual observation. Other 

 cases of interest would be those in which the angular 

 velocity of rotation varies with height above the earth's 

 surface and with distance from the centre of rotation. 

 Perhaps the most interesting point established in connexion 

 with the cases considered above is the very great importance 

 of the angular motion of the earth about its axis in relation 

 to cyclone and anticyclone motion. In this connexion it 

 would be of interest to determine the effect of small vertical 

 movements of the air in tending to bring the axis of the 

 cyclone more towards the vertical ; and this would probabiy 

 lead to results more in accordance with actual observations 

 than those which we have obtained above. I hope, how- 

 ever, to continue this investigation in a later paper. 



LIX. Precision - measurements in the X - Ray Spectra. 

 Part IV. — K- Series, the Elements Cu — Xa. By Elis 

 Hjalmar *. 



I 1ST a former part of this paper f Prof. M. Siegbahn has 

 given an account of a precision- measurement of the 

 Kc^-Iine in the region Cu — 01. I have continued these 

 investigations 



(1°) on the K /Si-line for the same elements ; and 



(2°) on the K« r and K^-lines in the following domain., 



S— Na. 



The first of these examinations was made with calcite as 

 analysing crystal, the latter with gypsum. 



The apparatus used, the new vacuum spectrograph with a 

 metallic X-ray tube, was described by Prof. Siegbahn | and 

 specially by Dr. W. Stenstrom |. The slit between the tube 

 and the spectrograph was for the measurements in the region 



* Communicated by the Author, 

 t Phil. Mag. xxxvii. June 1919. 



X W. Stenstrom, " Experimentelle Untersuchungen der Rontgen- 

 spektra," Diss., Lund, 1919. 



