78 



On Radiant Matter Spectroscopy. 



[Jan. 21, 



by sun or electric light and examined in the spectroscope it gives a 

 spectrum of black lines and bands as sharp and distinct as the 

 Fraunhofer lines. Fig. 2 shows the erbia spectrum by reflection. 

 It is strange that this most characteristic property has been recorded 

 by so few observers. Indeed, the only notice of it I have come 

 across is a passing remark of Professor Gleve's that "the light 

 reflected by dry erbia shows absorption-bands." 



Fig. 3 shows the absorption spectrum given by a solution of pure 

 erbic chloride. It differs in some respects from the drawings mapped 

 from older observations, as the absorption lines of holmia and thulia 

 are absent. The fine group of lines in the green of the reflection 

 spectrum is also absent in the absorption spectrum. 



The spectrum of bright lines emitted when erbia is rendered 

 incandescent in the blowpipe flame has been often observed, but the 



