788 



Mr. Ivar Maimer on the 



hitherto been done by Moseley, and for this purpose the 

 elements yttrium-silver, where Moseley has measured only one 

 wave-length, and among the following elements, cadmium- 

 antimony and barium-cerium, have been examined. 



The experimental arrangement appears from fig. 1, a 



Fig-. 1. 





2«^7S Ssw A 



1 



1 



\ 





1 



I 



N, 



revolving rocksalt crystal having been used in agreement 

 with M. de Broglie's method * in his researches on the high- 

 frequency spectra. The X-rays were limited to a com- 

 paratively fine beam by two lead-slits, 0'5 mm. wide, placed 

 at a distance of 11 cm. from one another. Between the 

 anticathode and the first slit the distance was about 30 cm. ; 

 from the second slit to the revolving axis of the crystal 

 4*5 cm., and from the second slit to the photographic plate 

 about 2Q cm. 



The rocksalt crystal was mounted on the vertical axis of 

 a clockwork, its reflecting surface containing the geometrical 

 axis of the revolving movement, another cleavage-plane 

 perpendicular to the axis. The angular velocity was 15° 

 per hour. Only the space where the two lines were expected 

 to be found was examined. The same space was passed over 

 several times, from three times in the case of silver to from 

 fifteen to twenty-five times for the earth-metals examined. 

 At all exposures an intensifying screen of zincblende in 

 close contact with the plate is used, in order to reduce the 

 time of exposure required. Unfortunately the lines, by this 

 method, show some want of sharpness and admit of less 

 precision when measured. Owing to the comparatively 

 feeble reflexion in the second order in the case of rocksalt,, 

 all spectra have been photographed only in the first order. 



* C. R. 17 Nov. 1913. 



