THE SUN ITS CHEMICAL ANALYSIS. 183 



less distinctness, the phenomenon of reversaL What is proved by 

 these phenomena? It is, that of all the rays of natural liftht which 

 traverse the artificial flame there are absorbed in greater abundance, 

 the rays which this jQame would emit were it alone shining; or, to 

 speak more scientifically^ the flame has an absorptive power corres- 

 pondent to its emissive power. 



Let us now represent to ourselves the sun consisting of a nucleus, the 

 focus of an incessant and intense ligl*t, and surrounded by an atmos- 

 phere. This envelope, which is of a temperature less elevated than 

 the central nucleus, will absorb in preference the rays similar to those 

 which it w^ould give out in greatest number if, supposing the globe of 

 the sun removed, the atmosphere remained as sole focus of light and 

 of heat. Here the solar atmosphere fulfils the part which the pale ar- 

 tificial flame did in the experiments of M. Bunsen, and the solar globe 

 that of the more vivid flame which reverses the bright lines of the arti- 

 ficial flame. The solar atmosphere, isolated from that which it en- 

 velopes, would furnish a spectrum, crossed with bright lines, corres- 

 ponding to all the substances which it might contain in ignition. 

 The intense light of the nucleus of the sun extinguishes all these lines, 

 and, in place of this imaginary spectrum of dark ground covered with 

 colored lines, it gives a spectrum of a bright ground covered with 

 dark lines. The spectrum of the sun is in some sort the negative 

 proof of the spectrum of its atmosphere; we find a dark line in the 

 place which corresponds to the bright line of sodium. We may affirm, 

 then, that this bright line would be found in the spectrum of the solar 

 atmosphere; or, in other terms, that sodium in ignition is present iu 

 that envelope. 



The sun reverses all the bright lines which its own envelope would 

 furnish; or, in other words, each of the dark lines of the spectrum 

 reveals negatively the presence of a particular simple body in the at- 

 mosphere of the central star. Now we count, in fact, thousands of 

 dark lines in the spectrum. How rich, then, in simple bodies must 

 be the orb which dispenses to us light and heat ! Many of these 

 lines occupy the places wdiich correspond to known terrestrial metals; 

 we may say, without hesitation, that the line D pertains to sodium, 

 another to lithium; here we see sixty black lines all coinciding with 

 the bright ones of iron, there the lines of calcium, of magnesium, of 

 sodium, metals so widely diffused over the surface of the earth; we 

 retrace the brilliant groups of chrome as black lines in the solar 

 spectrum. It was highl}^ interesting to search there for nickel and 

 cobalt, wdiicti are almost constant accompaniments of iron in me- 

 teorites. These two metals produce a very considerable number 

 of colored lines, less bright than those of iron. All the most vivid 

 lines of nickel are found reversed; that is, black, in the spectrum of 

 the solar light. We distinguish also a few of the lines of cobalt; but, 

 strange to say, not the brightest of those lines. Barium, copper, and 

 zinc appear to exist in small quantity in the solar atmosphere; on the 

 other hand, there has no distinct trace been discovered of gold, silver, 

 ' mercury, aluminium, silicium, which is so abundant among telluric 

 metals, cadmium, tin, lead, antimony, arsenic, strontian, and lithium. 



The discoveries of MM. Bunsen and Kirchoff no longer permit us 



