OF ARTS AND SCIENCES. 13 



In the first fluting at wave-length 3883.7 within the limit of ten 

 wave-lengths, over 2S of the spaces between the fine bright lines of 

 the flutings coincide with dark lines immediately in juxtaposition in 

 the solar spectrum. When we consider that the progressive arrange- 

 ment of these lines is exactly the same both in the spectrum of carbon 

 and that of the sun, we cannot consider that this coincidence is the 

 result of chance. On examining the spectrum of carbon in the region 

 near H still further, a remarkable number of coincidences of the 

 spaces between the bright lines of the carbon spectrum with dark lines 

 in the solar spectrum will be observed. We are led, therefore, to 

 conclude that the fluted spectrum of carbon is an example of the 

 reversal of the lines of a vapor in its own vapor. Fluted spectra 

 occur at comparatively low temperatures. When carbon is ignited, 

 we have at first a continuous spectrum. When the temperature in- 

 creases and the carbon is volatilized, fluted spectra occur, which 

 consist of interruptions of the continuous spectrum by fine line re- 

 versals occurring in harmonic order. The same phenomenon can be 

 observed in the spectrum of iron lines : through the centre of an iron 

 line, when a sufficient amount of iron vapor surrounds the Voltaic 

 arc in which iron is volatilized, reversal lines are always seen. Now 

 if the iron lines were arranged in regular order, the reversals would 

 also be in like regular order, and would coincide with similar reversals 

 in the solar spectrum. Assuming the conditions at the sun's surface 

 to be the same as those we have in the Voltaic arc, when carbon is 

 volatilized, the character of the carbon spectrum should exactly agree 

 with the character of the solar spectrum juxtaposed. This is found 

 to be true to a remarkable degree in comparing portions of the solar 

 spectrum with portions of the fluted spectrum of carbon beginning 

 at wave-length 3883.7. 



Our hypothesis leads us to conclude, that, at the point of the sun's 

 atmosphere where carbon is volatilized, so as to produce the peculiar 

 arrangement of reversals observed, the temperature of the sun ap- 

 proximates to that of the Voltaic arc. 



