High-Frequency Spectra of the Elements, 



705 



every time the spectrometer was exhausted, and under such 

 conditions the goldbeaters' skin had frequently to be 

 renewed. The spectrometer, which was specially designed 

 for this work, consists of a strong circular iron box of 30 cm. 

 inside diameter and 8 cm. high, closed by a lid which, 

 when the flange is greased, makes an air-tight joint. Two 

 concentric grooves are cut in the floor of the box. The 

 table A, which carries the plate-holder, rests on three steel 

 balls, of which two run in the outer groove, while the third 

 rests on the floor of the box. The position of the crystal- 

 table B is controlled in like manner by the inner groove. 

 This geometrical construction for a spectrometer is well 



Fig. 2 



known. The scales are fixed to the box and the verniers to 

 the tables. For these very soft rays the absorption by the 

 black paper front of the plate-holder became serious, and 

 two sheets of black tissue-paper were used instead. Lumps 

 of the pure elements, usually several millimetres thick, were 

 used as targets in the case of Mg, Al, Si, Mo, Ru, Pd, 

 Ag, Sb, Ta. Foils such as Rh, W, Au were either silver- 

 soldered or brazed onto copper. Os was used in the form of 

 a thin chemical deposit on copper. The alloys used were 

 ZrNi (70 per cent,), WFe (50 per cent,), NbTa (50 per 

 cent.), and SnMn (50 per cent.). KG1 and the oxides of 

 the rare-earth elements were rubbed onto the surface of 



