280 Lord Rayleigh and Prof. Ramsay. [Jan. 31, 



of F, and are very easily seen if there be not too much nitrogen, in 

 spite of the presence of some oxygen and water vapour. The approxi- 

 mate wave-lengths are 



487-91 .............. Strong. 



[486-07] ............. F. 



484"71 .............. Not quite so strong. 



480-52 .............. Strong. 



,- Q - Q .............. 1 Fairly strong charac- 



It is necessary to anticipitate Mr. Crookes' communication, and to 

 state that when the current is passed from the induction coil in one 

 direction, that end of the capillary tube next the positive pole appears of 

 a redder, and that next the negative pole of a bluer hue. There are, 

 in effect, two spectra, which Mr. Crookes has succeeded in separating 

 to a considerable extent. Mr. E. C. C. Baly,* who has noticed a similar 

 phenomenon, attributes it to the presence of two gases. He says : 

 " When an electric current is passed through a mixture of two gases, 

 one is separated from the other and appears in the negative glow." 

 The conclusion would follow that what we have termed " argon " is 

 in reality a mixture of two gases which have as yet not been sepa- 

 rated. This conclusion, if true, is of great importance, and experi- 

 ments are now in progress to test it by the use of other physical 

 methods. The full bearing of this possibility will appear later. 



The presence of a small quantity of nitrogen interferes greatly 

 with the argon spectrum. But we have found that in a tube with 

 platinum electrodes, after the discharge has been passed for four 

 hours, the spectrum of nitrogen disappears, and the argon spectrum 

 manifests itself in full purity. A specially constructed tube with 

 magnesium electrodes, which we hoped would yield good results, re- 

 moved all traces of nitrogen, it is true; but hjdrogen was evolved 

 from the magnesium, and showed its characteristic lines ' very 

 strongly. However, these are easily identified. The gas evolved on 

 heating magnesium in vacuo, as proved by a separate experiment, 

 consists entirely of hydrogen. 



Mr. Crookes has established the identity of the chief lines of the 

 spectrum of gas separated from air-nitrogen by aid of magnesium 

 with that remaining after sparking the air-nitrogen with oxygen in 

 presence of caustic soda solution. 



Professor Schuster also has found the principal lines identical in 

 the spectra of the two gases, as observed by the jar discharge at 

 atmospheric pressure. 



* < Proc. Phys. Soc.,' 1893, p. 147. 



