1889.] Nebula? and Stars ivith those of Comets and Aurora. 37 



Comets. 



- 



Duner's bands. 



Probable 



A of probable 







origins. 



origin. 



— 



461—451 



Bright space . . 





460—451 



— 



461—473 



(10) Dark space . . 





— 



468—474 



472—476 



Bright space . . 



C (hot) 



468—474 



— 



476—486 



(9) Dark space . . 





— 



483 







C (cool) 



483 



— 



495—486 



? Bright fluting . 



? 



— 



500 



495—502 



(8) Dark fluting . . 



Mg 

 C (hot) 



500 



517 



516—502 



Bright fluting . 



517 



519 







C (cool) 



519 



521 



516—522 



(7) Dark fluting . , 



Mg 

 Ba (2) 



521 



— 



524—527 



(6) Dark fluting . . 



526 



546 



544—551 



(5) Dark fluting . . 



Pb 



546 



558 



559—564 



(4) Dark fluting . . 



Mn (1) 



558 



561 







C (cool) 



561 



564 







C (hot) 



564 





585—594 



(3) Dark fluting . . 



Mn (2) 



586 



[615] 



616—630 



(2) Dark fluting . . 



Fe 



615 





647—668 



(1) Dark fluting . . 



? 





As I showed in the Bakerian Lecture, Mg 500, when not masked 

 by the broad carbon fluting at 517, is probably indicated by the dark 

 band, for which Duner gives the value 502 to 495, so that this may 

 also be regarded as common to Group II stars and comets. 



The cool carbon flutings are seen in comets, but not in stars of 

 Group II, the reason being that the temperature is too great. The 

 hot carbon fluting at 564 is in all probability present in stars of 

 Group II, but is always masked, in some cases by continuous 

 spectrum, and in others by the absorption fluting of manganese, which 

 is nearly coincident with it. 



The line, or probably fluting, at 495 has not yet been recorded in 

 comets, but its association with the fluting at 500 in Nova Cygni 

 indicates tha.t its apparent absence is entirely due to incomplete 

 observations. 



The second fluting of manganese, near 586, though one of the most 

 prominent in stars of Group II, has not been observed in cometary 

 spectra, probably because there is not sufficient continuous spectrum 

 from the sparse meteoritic background of the comet to produce the 

 absorption of more than the first fluting of manganese. 



Duner's band 1, 647 to 668, has not yet had an origin assigned 

 to it. 



V. General Comparisons. 



In the preceding tables I have shown that the spectra of nebula?, 

 auroras, bright-line stars, and stars of Group II are closely related to 

 the spectra of comets. In the table which follows all the spectra are 



