348 



Mr. H. F. New-all 



[Feb. 21, 



length 370, the agreement is all that we could hope for, taking into 

 account the fact that my measurements were not made with a view of 

 giving a final and carefully-considered set of measurements of wave- 

 lengths, but between H Y and Hp there is a systematic difference of 

 about 3 tenth-metres, which I am unable at present to account for. 

 The agreement of grouping and intensity, however, leaves no doubt 

 as to the identity of the spectrum of my low-pressure lines with the 

 spectrum of argon. I have reduced my measurements with reference 

 to Rowland's scale of wave-lengths, and I infer from the value 

 adopted for the Hp (F) line, that Angstrom's scale has been used in 

 Mr. Crookes' reduction. The difference between the scales is not 

 enough to account for the discrepancies above referred to. 



The experiments were repeated, with slight variations, several 

 times with results which, so far as the spectrum of argon is concerned, 

 were constant. But it was noted that continued passage of the dis- 

 charge appears to result in the attaining of a certain minimum pres- 

 sure, after which there is slight and slow rise to a tolerably-fixed 

 pressure. It is not necessary to dwell on these points in the present 

 note. 



It is interesting to find argon asserting itself, unsolicited, in quite 

 new circumstances, and under conditions which practically constitute 

 one more mode of separating argon from nitrogen namely, the 

 getting rid of nitrogen by passing electric discharge through it in 

 the presence of hydrogen or moisture and acid. 



Table of Wave-lengths. 



