2 



Prof. J. N. Lockyer. 



[Nov. 21, 



The wave-lengths of these lines have been determined by means of 

 a Steinheil spectroscope having four prisms, comparisons being made 

 with adjacent metallic lines, and the positions interpolated by micro- 

 metric measurements ; the accuracy may perhaps be taken to be 

 within 0*1 tenth metre. Other lines have been noted, but they are 

 not included in the list, for the reason that their wave-lengths have 

 not yet been determined with the dispersion stated above. 



Of the lines in the foregoing list, six are in all probability coinci- 

 dent with chromospheric lines, as shown in the following table, which 

 also indicates the frequencies and brightnesses of the lines according 

 to Young : — 



Wave-length of Chromospheric Lines. 



(Angstrom's scale). 



Rowland's scale). 



Frequency. 



Brightness. 



6121 *2 



6122 -4 



5 



3 



6064-5 



6065 -7 



5 



2 



5990-0 



5991-6 



10 



4 



5874 -9 (D 3 ) 



5875 -9 



100 



90 



5428-8 



5429 -9 



8 



3 



5403 -1 , 



5404 -1 



5 



3 



It is important to point out that all these lines do not appear in 

 the spectrum at the same time. For instance, in the first two speci- 

 mens of the mineral no trace of D 3 was noted, but in the third 

 portion examined, all coming from the same specimen, D 3 appeared 

 as a pretty bright line. Again, as in the case of a previous operation 

 on broggerite,* in one experiment with eliasite the products of dis- 

 tillation, collected in four stages, gave different spectra. 



These facts seem to indicate that the gas obtained from eliasite is 

 either a compound or a mixture of gases, just as is that obtained 

 from broggerite according to former experiments. 



It is also to be remarked that among the lines in the eliasite 

 spectrum, those at 6122*4 and 6065*7 have been recorded in the gases 

 obtained from cleveite, and 6122*4 has also been noted in the ga& 

 obtained from gummite. 



It seems to be more than probable, therefore, that the lines 

 observed in eliasite indicate a new gas, in some way associated with 

 those given off by cleveite and broggerite, and the fact that D 3 is not 

 necessarily present in the spectrum, furnishes an additional argu- 

 ment in favour of the view that the gas obtained from cleveite or 

 broggerite is complex. 



* < Eoy. Soc. Proc.,' vol. 58, p. 194. 



