The Piscian Stars. 



139 



In favour of the real existence of bright lines, Professor Hale points 

 out that the contrast between the line and the continuous spectrum 

 increased rather than diminished when dispersion was increased, and 

 that there was no decrease in contrast as the slit was widened. The 

 question, however, is so complicated by the presence of the carbon 

 fluting and other absorptions, that I shall not follow Professor Hale in 

 his definite conclusions as to bright lines upon these grounds. 



Before we can admit the certain presence of bright lines in 152 

 Schj., we must consider whether similar appearances occur in other 

 stars where bright lines have not been previously suspected. As a 

 matter of fact, in the photographic spectra of a Tauri, /3 Andromedse, 

 and aOrionis, which I published in 1893,* the spectra might, so far as 

 mere appearance goes, be regarded as containing both bright and dark 

 lines, some of the bright spaces between obvious dark lines being very 

 conspicuous ; the same remark applies in a less degree to the spectrum 

 of Arcturus which I published at the same time. But we find a com- 

 plete explanation of these spectra if we regard them as consisting of 

 dark lines, whereas if we take the bright spaces we cannot match them 

 at all. We do not hesitate in these cases to treat the spectra as 

 consisting of dark lines only, the apparent bright lines being simply 

 spaces between dark ones. I find that practically in all dark line 

 spectra where the lines are from some cause or other thick, the inter- 

 A'als between them are apt to appear as bright lines, and this bright- 

 ness can readily be intensified by purely photographic processes. 



I have accordingly thought it unnecessary to modify the division 

 into species on account of the supposed presence in some of them of 

 bright lines. If the presence of bright lines be eventually established, 

 may they not indicate that M^e are observing the eff'ects of volcanic 

 gases floating over a " photosphere " which has attained the consistency 

 of lava 1 



Bearing on the Meteoritic Hypothesis. 



The photographs taken by McClean and Hale have now suflSciently 

 shown that there is much in common between the line spectra of the 

 Antarian and Piscian stars. This indicates that there is a practical 

 equality of mean temperature in the reversing layers of the two groups, 

 but we find a very great difference in the conditions as to carbon ; 

 while carbon is undoubtedly absorbing in the Piscian stars, it is cer- 

 tainly not absorbing in the Antarian, and there is in fact strong 

 evidence that it is radiating.! 



We cannot imagine different kinds of stars of the same temperature 

 as representing the same stage in any evolutionary scheme, so that the 



* ' Phil. Trans.,' A, vol. 18G (1893), plate 23. 



t 'Eoy. Soc. Proc.,' vol. 44- (1888), p. 52; * PMl. Trans.,' A, vol. 186 (1893), 

 p. 704. 



