174 Mr. J. N. Lockyer. Researches in Spectrum [Dee. 12. 



duction ? I find these blue bands with common salt, but they have 

 neither the definiteness nor the brilliancy of the lithium band. When 

 lithium wire burns in air it emits a somewhat crimson light ; plunge 

 it into oxygen, and the light changes to bluish-white. This seems to 

 indicate that a high temperature is necessary to bring out the bine 

 ray." 



Postscript, November 22, 1861. — " I have just made some further 

 experiments on the lithium spectrum, and they conclusively prove 

 that the appearance of the blue line depends entirely on the tempera- 

 ture. The spectrum of lithic chloride, ignited in a Bunsen's burner 

 flame, does not disclose the faintest trace of the blue line ; replace the 

 Bunsen's burner by a jet of hydrogen (the temperature of which is 

 higher than that of the Bunsen's burner) and the blue line appears, 

 faint, it is true, but sharp and quite unmistakable. If oxygen now 

 be slowly turned into the jet, the brilliancy of the blue line increases 

 until the temperature of the flame rises high enough to fuse the 

 platinum, and thus put an end to the experiment." 



These observations of Professors Tyndall and Frankland differen- 

 tiate this blue line from those which are observed at low temperatures. 

 The line in the violet to which I have already referred is again 

 differentiated from all the rest by the fact that it is the only line in 

 the spectrum of the sun which is strongly reversed, so far as our 

 present knowledge extends. The various forms of lithium, therefore, 

 >may be shown in the following manner. 



Fig. 5. 











SUN 







ARC 





■ r 



FEEBLE SPARK 



T 1 



FLAME 







It is remarkable that in the case of this body which at relatively 

 low temperature goes through its changes, its compounds are broken 

 up at the temperature of the Bunsen burner. The spectrum, e.g. of 

 the chloride, so far as I know, has never been seen. 



Hydro gen . 



All the phenomena of variability and inversion in the order of in- 

 tensity presented to us in the case of calcium can be paralleled by 

 reference to the knowledge already acquired regarding the spectrum 

 of hydrogen. 



Dr. Frankland and myself were working together on the subject in 

 1869. In that year ("Proc. Hoy. Soc," No. 112) we pointed out 



