14 KEPORT 1891. 



of the corona. The green coronal line has no known representative in 

 terrestrial substances, nor has Schuster been able to recognise any of our 

 elements in the other lines of the corona. 



The spectra of the stars are almost inBnitely diversified, yet they can 

 be arranged with some exceptions in a series in which the adjacent 

 spectra, especially in the photographic region, are scarcely distinguish- 

 able, passing from the bluish-white stars hke Sirius, through stars more 

 or less solar in character, to stars with banded spectra, which divide- 

 themselves into two apparently independent groups, according as the- 

 stronger edge of the bands is towards the red or the blue. In such an 

 arrangement the sun's place is towards the middle of the series. 



At present a difference of opinion exists as to the direction in the series 

 in which evolution is proceeding, whether by further condensation white 

 stars pass into the orange and red stages, or whether these more coloured 

 stars are younger and will become white by increasing age. The latter 

 view was suggested by Johnstone Stoney in 1867. 



About ten years ago Ritter, in a series of papers, discussed the behaviour 

 of gaseous masses during condensation, and the probable resulting con- 

 stitution of the heavenly bodies. According to him, a star passes through 

 the orange and red stages twice, first during a comparatively short 

 period of increasing temperature which culminates in the white stage, and 

 a second time during a more prolonged stage of gradual cooling. He- 

 suggested that the two groups of banded stars may correspond to these- 

 different periods : the young stars being those in which the stronger 

 edge of the dark band is towards the blue, the other banded stars, which 

 are relatively less luminous and few in number, being those which ar& 

 approaching extinction through age. 



Recently a similar evolutional order has been suggested, which is based 

 upon the hypothesis that the nebulae and stars consist of colliding meteoric 

 stones in different stages of condensation. 



More recently the view has been put forward that the diversified 

 spectra of the stars do not represent the stages of an evolutional progress, 

 but are due for the most part to differences of original constitution. 



The few minutes which can be given to this part of the address are 

 insufficient for a discussion of these different views. I purpose, therefore, 

 to state briefly, and with reserve as the subject is obscure, some of the 

 considerations from the characters of their spectra which appeared to me to 

 be in favour of the evolutional order in which I arranged the stars from 

 their photographic spectra in 1879. This order is essentially the same 

 as Vogel had previously proposed in his classification of the stars in 

 1874, in which the white stars, which are most numerous, represent the 

 early adult and most persistent stage of stellar life, the solar condition 

 that of full maturity and of commencing age ; while in the orange and red 

 stars with banded spectra we see the setting in and advance of old age. 



