Trowbridge and Ilutchins — Carbon in the Sun. 347 



lines may thus appear which are wanting when the tempera- 

 ture falls. One is forced to these conclusions in observing the 

 conditions under which the varying character of metallic spec- 

 tra are produced. For instance, we have caused the rays from 

 iron vapor to traverse a long and dense layer of iron vapor, 

 and have observed that the strength of the lines and the num- 

 ber of reversals have been largely increased. In another ex- 

 periment, the lower carbon of the electric lamp we employed 

 occupied the center of an electro-magnet. This was accom- 

 plished by passing the carbon through a hollow iron cone, and 

 surrounding the latter by layers of wire, through which the 

 electrical current employed in generating the light passed. In 

 this case the electric arc was spread out at right angles to the 

 pole of the magnet, into a fan-like, intensely hot flame which 

 roared loudly, and which rarefied, so to speak, the iron vapor 

 between the carbon terminals. The strength of the lines and 

 the number of reversals were diminished under this new con- 

 dition. 



Another phenomenon may happen. When an excess of the 

 vapor of one metal floats over or is mixed with that of another, 

 the lines of one metal are superimposed upon those of another 

 in the solar spectrum, and the stronger spectrum of one ele- 

 ment may easily obliterate the weaker spectrum of another. 

 Thus we have succeeded in completely obliterating the fluted 

 spectrum of carbon in the green and blue, by photographing 

 upon it the spectrum of iron, of nickel, and cerium. A species 

 of composite photograph was thus obtained. It is possible 

 that in the future Gmlton's ingenious method of composite pho- 

 tography may be applied to the solar spectrum ; and by a judi- 

 cious selection of photographs of the elements, a composite 

 photograph may be obtained which closely resemble portions 

 of the solar spectrum, and will enable us to judge of the com- 

 position of the reversing layers of the sun. 



To the varying conditions which we have thus outlined are 

 due, we believe, the disappearance in the sun's spectrum of the 

 marked fluted spectrum of carbon in the green and blue por- 

 tions. 



A careful examination of the fluted spectrum of carbon, 

 however, with the juxtaposed solar spectrum, discloses a re- 

 markable fact: while traces of obliteration of the evidence of 

 carbon vapor are seen, yet the general character of the lines in 

 the solar spectrum immediately juxtaposed with the fluted 

 spectrum of carbon near H lead us to believe that there is 

 unmistakable evidence of the existence of carbon vapor in the 

 sun. When the arrangement of the fine lines of the spectrum 

 of carbon is plotted as a curve, and that of the dark lines in 

 the solar spectrum immediately above the carbon spectrum is 



