Spectra of the Elements Tantalum— Uranium. 41 



This consists of a microinetric [AA] adjustable cone [C] 

 carefully ground. The air is then constantly streaming 

 through the holes [BB] and the conic opening. The 

 delicate regulation of the vacuum was done through altering 

 the resistance of the air-pump motor. 



Fig. 2. 



The attachment of the substances on the anticathode has 

 been already described in the case of Au-U *. Of the 

 elements now examined Ta, Ir, and Pt in metal form were 

 soldered on the anticathode, while Os as a salt, Ra as radium 

 bromide, Th as thorium oxide, W and U in powder form were 

 rubbed on it. Po was examined in the form of an electrolytic 

 deposit on a piece of sheet-copper. 



Results, 



The results of the measurements are given in the Tables L- 

 XIV. In the first column the notation of most of the lines 

 is to be found, and in the second the relative intensities of 

 the lines under the assumption of the value 10 for the 

 strongest a-line («i). The third column contains the 

 glancing angles of reflexion, and the fourth the wave- 

 lengths calculated from the formula X — 2d sin $, where 

 \og2d has been taken to be 0*75035. In the last column 



are the values of \J - . The accuracy of the measurements 

 is estimated to about 0*3 per cent. 



* Siegbahn and Friman, Phil. Mag. I. c. 



