Fluorescence produced by Ultra-Schumann Rays. 451 



and was so placed that the stream delivered by it passed 

 directly over the slits, i. e. through the fluorescent jet. 



The arrangement of the plate A, slit S, lower electrode B, 

 and the tube T can also be seen in the small sectional diagram 

 of' fig. 1, which is drawn as seen by an observer looking from 

 the direction of the spectroscope. 



The glass window W 2 was introduced for the purpose of 

 determining whether the radiations from the spark were 

 coming up through the slit properly. 



During some of the experimental work, all lines along 

 which parts of the apparatus joined were sealed up with wax, 

 and the bottom of the box J was sealed with mercury. 

 During other parts of the work the lines of juncture were left 

 unsealed. 



The spark was produced by a \ kilowatt, 110 volt, GO cycle 

 transformer. Across the spark-gap was placed a condenser 

 •consisting of 30 copper plates, 15 X 20 cm., insulated by 

 ordinary window-glass, the whole being immersed in oil. 

 No influence of the nature of the spark upon the nature o(: 

 the fluorescent spectrum of the jet was ever ascertained, 

 except that a strong spark gives a more intense fluorescence 

 than a weak one. The authors do not feel able to state, 

 however, that there is no influence at all upon the nature of 

 the fluorescence, the difficulty of: ascertaining such an in- 

 fluence lying in the fact that it is difficult to vary the spark 

 and keep all other conditions constant. 



The Fluorescent Spectrum in Various Gases. 



In the work of Wood and Hemsalech above referred to, it 

 was found that the strongest fluorescence of the jet was 

 obtained when nitrogen was used in the jet-chamber, the 

 spectrum then consisting of the water band X30G4A.U., 

 and under favourable circumstances the nitrogen bands. 

 Their nitrogen, however, contained impurities, especially 

 oxygen ; and the present authors thought it to be of interest 

 to determine the effect of removing the last trace of oxygen. 

 Nitrogen obtained from a bomb was accordingly cleared 

 of the oxygen it contained by the method described by 

 C. Van Brunt*, dried, and passed into the jet-chamber. 

 Plate VI. fig. 1 shows the spectrum with commercial 

 nitrogen, containing about 1 per cent, oxygen. Fig. 2 

 shows the effect of removing the oxygen. The horizontal 

 line in these photographs is the continuous spectrum due to 

 ■the light from the spark diffusely reflected by the upper 



* Journ. American Chem. Soc. July 1914. 

 2G2 



