166 THE CHEMISTRY OF THE SUN. [CHAP. 



both, follows, both from our observations and experiments. The 

 separate prior observations of both of us have shown : 



" 1. That a gaseous condition of the photosphere is quite con- 

 sistent with its continuous spectrum. The possibility of this con- 

 dition has also been suggested by Messrs. De la Rue, Stewart, and 

 Loewy. 



"2. That the spectrum of the photosphere contains bright lines 

 when the limb is observed, these bright lines indicating probably an 

 outer shell of the photosphere of a gaseous nature. 



"3. That a sun-spot is a region of greater absorption. 



" 4. That occasionally photospheric matter appears to be in- 

 jected into the chromosphere. May not these facts indicate that the 

 absorption to which the reversal of the spectrum and the Fraun- 

 hofer lines are due takes place in the photosphere itself, or ex- 

 tremely near to it, instead of in an extensive outer absorbing 

 atmosphere ? And is not this conclusion strengthened by the con- 

 sideration that otherwise the newly discovered bright lines in the 

 solar spectrum itself should be themselves reversed on KirchhofFs 

 theory ? This, however, is not the case. We do not forget that 

 the selective radiation of the chromosphere does not necessarily 

 indicate the whole of its possible selective absorption ; but our 

 experiments lead us to believe that were any considerable quantity 

 of metallic vapours present, their bright spectra would not be 

 entirely invisible in all strata of the chromosphere." 



Our view received, apparently, very strong confirmation after- 

 wards. In my own observations occasionally in passing over a 

 metallic prominence, the spectrum would be " full of lines " ; 

 and during the eclipse of 1870, at the moment of disappear- 

 ance of the sun, the same effect was noticed ; we had, to quote 

 Prof. Young, " A sudden reversal into brightness and colour of 

 the countless dark lines of the spectrum at the commencement 

 of totality." The instrument used was an integrating spectro- 

 scope directed to the sun. In 1871 Captain Maclear and 

 myself watched these lines on the retreating cusps. On these 

 observations was based the view that there was a region some 

 2" high above the photosphere which reversed for us all the 



