76 THE CHEMISTRY OF THE SUN. [CHAP. 



terrestrial rocks, to throw their spectra on the screen, and to 

 map them with considerable minuteness ; and we say we have 

 the spectrum of such and such a meteorite, or of such and 

 such a rock. Similarly we can get the spectrum of iron in the 

 same way, and we are considerably astonished at the wonderful 

 similarity of the results thus obtained. 



Now chemistry has advanced to a certain stage, and low tem- 

 perature chemistry comes in and shows us that this meteorite 

 or rock may be an excessively complicated substance. The 

 same chemistry applied to iron shows that nothing can be done 

 with it. But to say that iron cannot be broken up because low 

 temperature chemistry fails to break it up is an assumption, for 

 as we undoubtedly get the lines of the constituents of the rock, 

 or of the meteorite, recorded in the spectrum, we may also be 

 registering the lines of the constituents of iron ; and it is fair 

 to say this, because we know that in the electric spark we have 

 a stage of heat at which at present no chemical experiment 

 whatever has been made. 



Passing on from that point however I will next consider 

 somewhat more in detail that part of Kirchhoff s work which 

 deals with the connection between the solar spectrum and the 

 spectra of the chemical elements, 1 and again I quote from the 

 translation of his memoir by Professor Roscoe : 



" As soon as the presence of one terrestrial element in the solar 

 atmosphere was thus determined, and thereby the existence of a 

 large number of Fraunhofer's lines explained, it seemed reasonable to 

 suppose that other terrestrial bodies occur there, and that, by exert- 

 ing their absorptive power, they may cause the production of other 

 Fraunhofer's lines. For it is very probable that elementary bodies 

 which occur in large quantities on the earth, and are likewise dis- 

 tinguished by special bright lines in their spectra, will, like iron, 

 be visible in the solar atmosphere. This is found to be the case 

 with calcium, magnesium, and sodium. The number of the 



1 Researches on the Solar Spectrum. Roscoe's translation, part i. p. 20. 



