450 Mr. C. F. Meyer and Prof. R. W. Wood on 



Apparatus. 



Referring to fig. 1, A is a circular copper plate 3 mm. 

 thick and 7*5 cm. in diameter, part of the plate being- 

 represented in the diagram as cut away. The plate rested 

 on and was sealed to a short piece of brass tubing 7 cm. in 



Fin-. 1. 



diameter and 1 cm. long, which in turn was soldered over an 

 opening of nearly as great diameter in the bottom of the 

 metal box J. Through a hole in the centre of this plate a 

 truncated portion of a copper rivet had been driven. The rivet 

 had a vertical slit S cut into it, 2 mm. long and *2 mm. wide. 

 B is a piece of heavy copper wire. The copper rivet in the 

 centre of plate A and the wire B served as terminals between 

 which a spark from a transformer was passed. The radiation 

 from the spark passed up through the slit S into the jet- 

 chamber J, together with the ordinary visible and ultra-violet 

 light. The special radiation, which we may call ultra- 

 Schumann radiation, causes a short jet of ultra-violet fluor- 

 escence in the air or other gas above the slit S in the 

 jet-chamber J. This fluorescence was photographed through 

 the quartz window W, by means of the quartz spectroscope 

 represented diagrammatically by the lenses L, the prism P, 

 and the photographic plate Q. The spectroscope had had its 

 slit-tube removed, the jet itself serving as slit. The auxiliary 

 chamber K is added to the apparatus in order to ensure a 

 dark background. The chambers J and K (13 x 9 x 9 cm.), 

 which consisted of metal boxes blackened inside, served as a 

 dark enclosure, and also as a container for the particular gas 

 in which it might be desired to study the jet. 



The tube T served for the introduction of the desired gas, 



