348 Troiobridge and Hutchins — Carbon in the Sun. 



also plotted, the two curves have a remarkable similarity in 

 character, running with a slight convexity toward one axis. 



In the first fluting at wave-length 3888*7 within the limit of 

 ten wave-lengths, over 28 of the spaces between the fine bright 

 lines of the flu tings coincide with dark lines immediately in 

 juxtaposition in the solar spectrum. When we consider that 

 the progressive arrangement 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 ex- 

 amining the spectrum of carbon in the region near H still fur- 

 ther, 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 car- 

 bon is ignited, we have at first a continuous spectrum. When 

 the temperature increases and the carbon is volatilized, fluted 

 spectra occur, which consist of interruptions of the continuous 

 spectrum by fine line reversals occurring in harmonic order. 

 The same phenomenon can be observed in the spectrum of iron 

 lines: through the center 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 rever- 

 sals 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 spec- 

 trum should exactly agree with the character of the solar spec- 

 trum juxtaposed. This is found to be true to a remarkable 

 degree in comparing portions of the solar spectrum with por- 

 tions of the fluted spectrum of carbon beginning at wave- 

 length 38837. 



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

 sun's atmosphere where the carbon is volatilized, so as to pro- 

 duce the peculiar arrangement of reversals observed, the tem- 

 perature of the sun approximates to that of the voltaic arc. 



