of Gases excited by Ultra- Schumann Waves. 901 



i. e. that it is merely the spark aureole projected through 

 the hole. 



Steubing's adverse criticism was quite adequately answered 

 at the time. Most of the results which lie obtained, were 

 undoubtedly due to dust particles, which should have been 

 eliminated. 



The photographs illustrating this paper, of the jet in 

 different gases, made with a quartz lens through a quartz 

 prism, show that the spectrum differs according to the gas 

 employed. The spark passed always in air in a closed 



Fiff. 1. 



i 



chamber, and the entrance of the other gas was prevented 

 by keeping an excess pressure in the spark-chamber. 



We took up the subject anew during the post autumn, and 

 though we have taken over two hundred photographs, we do 

 not feel that we have accomplished much more than to 

 determine the conditions under which future work must be 

 done. We have, however, discovered many extremely 

 curious phenomena, some of which are still quite inexpli- 

 cable, but which can be reproduced over and over again with 

 absolute certainty. Most remarkable are the effects obtained 

 with moving and stationary gases : some gases showing a 

 much more brilliant fluorescence when moving across the 

 jet of rays from the spark, others responding vigorously to 

 the excitation when quite stagnant, but showing no luminosity 



Phil Mag. S. 6. Vol.27. No. 161. May 1914. 3 



