288 



Prof. Richardson and Lieut. Bazzoni on the 



throw the electron into a circle of known radius. By a 

 continuous variation of the magnetic field one is able to get 

 a spectrogram of a complex radiation similar to that obtained 

 for infra-red radiation with, for example, a rock-salt prism 

 and a thermopile, but in this case the spectrum obtained is 

 not a pure one ; so that it is not in general particularly 

 suitable for locating individual lines. The method, in fact, 

 is similar to one used by Ramsauer * in investigating the 

 velocity distribution of photoelectrically emitted electrons. 



Fig. 1. 



Horizontal cross-section of apparatus. Drawn to scale. 



The apparatus finally developed is shown in fig. 1. The 

 tube is made entirely of transparent quartz. The metallic 

 parts are all of copper without solder, excepting the fila- 

 ment which is of tungsten and the sealing-in wires which 

 are of molybdenum. The leading-out arms are all 10 to 

 11 cm. long and are sealed at the ends with the usual lead- 

 molybdenum seals made by the Silica Syndicate. The 

 tungsten filament, which is 1 cm. long and is used as a 

 thermionic source of electrons for exciting the radiation, is 

 shown at F. It is supported from a side tube in such a way 

 * Sitz. der Heidelterger Alu d. Wiss. 22£July, 1914. 



