On the Chemistry of the Hottest Stars. 



157 



prominences ; and now, for the first time, a longer and thinner line 

 appears, occasionally noted as widened in spots ; while, last of all, 

 we get, very long, very delicate relatively, two lines constantly seen 

 widened in spots, and another line, not seen in the spark, and never 

 yet recorded as widened in spots.'* 



" Similar observations in the same part of the spectrum were 

 made by Professor Turner in 1886.f His observations were made 

 under less favourable conditions than those in Egypt, and in the 

 absence of statements as to the relative lengths of the lines observed, 

 it is impossible to utilise them. 



" This is one of the most important points in solar physics, but 

 there is not yet a concensus of opinion upon it. Professor Young* 

 and others, apparently, still hold to the view first announced by Dr. 

 Frankland and myself in the infancy of the observations, that the 

 Fraunhofer absorption takes place in a thin stratum, lying close to 

 the photosphere." 



I next proceeded to discuss the numerous photographs obtained 

 during the eclipse, and I gave a map showing that there was only 

 the slightest relation between the intensities of the lines common to 

 the Fraunhofer and the eclipse spectrum, and further, that only a 

 few of the Fraunhofer line3 are represented at all. Not only this, 

 but in the eclipse photographs there are many bright lines not 

 represented at all among the Fraunhofer lines. 



The chromosphere, then, is certainly not the origin of the Fraun- 

 hofer lines, either as regards intensity or number. From the eye 

 observations made since 1868, there is ample evidence that the 

 quiescent chromosphere spectrum indicates a higher temperature 

 than that at which much of the most valid absorption takes place ; 

 in other words, that the majority of the lines associated with lower 

 temperature are produced above the level of the chromosphere. 



The eclipse photographs, however, at the same time afford evi- 

 dence by the relative lengths of some of the lower temperature lines 

 that we need not locate the region which produces them at any 

 great height above the chromosphere. 



The solar evidence, then, is that most of the line absorption is 

 produced in, and not very far above, the chromosphere. This is a 

 conclusion we are bound to accept in a discussion of the origin of 

 stellar absorption in the absence of evidence to the contrary. 



We have no right to assume that the absorption will be pro- 

 duced at the top of the atmosphere in one star, and in the bottom 

 in another, when the atmospheres are once relatively quiescent. 



* 4 Koy. Soc. Proc.,' vol. 34, p. 297. 



f ' Phil. Trans.,' 1889, vol. 180, A, p. 391. 



