1035 



when the current passes, the nitrogen will be principally ionised. The 

 spark will therefore show the nitrogen-spectrum. This was actually 

 observed by Bouty ') and was recently confirmed by Hamburger's 

 measurements. ') 



In conclusion we wish to express, our sincere thanks to Dr. G. L, 

 F. Philips for the opportunity given to us of carrying out this 

 investigation. 



Eindhoven. Physical Laboratory of 



Philips's Incandescent lamp- factory . 



1) Bouty, Journ. de Pliys. (1904), p. 605. 



2) Hamburcjer, Diss. Delft 1917. 



