56 Mr. J. S. Ames on some Gaseous Spect?*a. 



the lines at w.-l. 4790*0 and 4077*98 (4078*31 and 4077*32 on 

 his scale) are interchanged : 4079*0 is the hydrogen-line, 

 4077*98 the mercury one. This is at once seen on viewing 

 Prof. Kowland's photographs. 



There is the possibility that some of the lines which I have 

 attributed to hydrogen are due to sulphur, as its ultra-violet 

 spectrum is not known. I am at present engaged on this 

 spectrum, however, and shall soon be able to decide whether 

 or not my present list of hydrogen-lines is correct. 



Nitrogen. 



The spectra of air and its constituents have been studied 

 with special care by Wiillner *, Hasselberg t, and Deslandres J. 

 In this paper I do not wish to refer to any of the disputed 

 points concerning the immediate cause of the different groups 

 of bands in the spectrum of ordinary air or nitrogen, but 

 merely to give measurements of the lines which form the 

 "second group " of nitrogen, and to mention some of its 

 properties. 



In this group there are nearly fifty bands, each band con- 

 sisting of three series, the three first lines of each forming a 

 " head " for the band. The bands all have their heads 

 towards the red end of the spectrum, while the group itself 

 is turned the opposite way. At first sight the bands are 

 gathered in companies of five, except towards the head of the 

 group, where there is a series of two bands, then one of three, 

 one of four, and finally the sequence of fives. It seems as if 

 the group should begin with a single band ; but I have 

 sought it in vain. The three lines forming the heads are 

 double for all the series, without exception I think. 



In the following Table the wave-lengths refer to the second 

 line in each head. The first column gives my measurements 

 of the wave-lengths in air ; the second the corresponding 

 wave-numbers ; the third the measurements of the wave- 

 lengths by Hasselberg and Deslandres. 



* See Wied. Ann. xxxviii. (1889) for references. 



t MSm. de VAcad. imp. St. Petersb. xxxii. p. 15 (1885). 



| Ann. Chem. et Phys. [6] xiv. (1888). 



