x*.] RESULTS. 277 



red absorptions were independent of each other, for they varied 

 with temperature. 



We found that the temperature reached by the tube could be 

 marked by the following phenomena : 



I. When the continuous spectrum of the tube extended to D 

 this line not being visible. 



II. When it extended beyond D, D being bright. 



III. When it extended into the green, D being very bright. 



IV. When it extended beyond the green, D being invisible. 



Before I detail some of the results of this inquiry I should 

 state that Professor Roscoe, who had seen some of the earlier ex- 

 periments, also took the matter up, and commanding a higher 

 temperature than was at first at our disposal, observed some 

 previously unrecorded spectra in the case of sodium and potas- 

 sium. These I shall call the new spectra. They are always 

 easily visible when a sufficient temperature has been reached. 



The results obtained were as follows : 



Hydrogen 



Nitrogen ' NQ &b Qn 



Mercury 



Bismuth 



Zinc. 



Cadmium, i . , , . 



\ Continuous absorption in the blue. 

 Antimony, f 



Phosphorus. 



Sulphur. Fluted spectrum (previously observed by Salet). 



Iodine. Fluted spectrum in the green, and intense band of 



general absorption in the violet where, at the 



ordinary temperature, the vapour transmits light. 

 Sodium. There were observed either separately or together 



a. D absorbed. 



/?. Continuous absorption breaking up in the 

 middle into red and blue absorption. 



y. The new spectrum. . 



