Researches in Solar Chemistry. 165 



pure spectrum of that substance, but of that substance as it 

 generally exists in an impure state. 



The spectrum will be found rich in lines ; and when very 

 considerable care is employed, one may go away with the idea 

 that in iron, for instance, all the lines which are observed in 

 the spectrum of iron coincident with Fraunhofer lines repre- 

 sent coincidences in the case of each line with iron in the sun 

 and iron in our laboratory. But the more the work is carried 

 on, the more one finds that the complex spectra which are ob- 

 served are really much more simple when all the impurities 

 are taken into account. 



In the region of the solar spectrum, for instance, recorded 

 on the map exhibited we have a great many iron-lines ; but 

 before the method of determining impurities was utilized, the 

 spectrum was very much richer than it is at present ; possibly 

 one fourth of the lines have been withdrawn. In every specimen 

 of iron which has been used in this work the lines of calcium, 

 aluminium, and some of the lines of manganese and cobalt have 

 been represented ; and no chemist will wonder at this result. 

 But there is a very curious thing which chemists, I think, will 

 wonder at. In this part of the spectrum there were two lines 

 which, by their thickness both in the solar and iron spectra, 

 seemed undoubtedly to belong to iron ; but further inquiry led 

 to this extraordinary result — that one of these lines in all proba- 

 bility has its origin in the vibration of molecules of tungsten, 

 the other being probably a line of molybdenum. Grlucinum 

 is another metal which may be referred to in this connexion ; 

 and it would appear that it is almost impossible to get a spe- 

 cimen of iron which does not contain, not only calcium and 

 aluminium, but others which we consider rare metals on the 

 earth, such as tungsten, molybdenum, and glucinum. 



A few years ago, taking the work of KirchhofF, Bunsen, 

 Angstrom, and Thalen into consideration, and connecting it, 

 so far as one could connect it, with those ideas of which recent 

 eclipses have been so fruitful, our chemical view of the sun's 

 atmosphere was one something like this : — We had, let us say, 

 first of all an enormous shell of some gas, probably lighter 

 than hydrogen, about which we know absolutely nothing, 

 because at present none of it has been found here ; inside this 

 we have another shell, of hydrogen ; inside this we have another 

 shell, of calcium, another of magnesium, another of sodium, 

 and then a complex shell the section of which has been called 

 the reversing layer, in which we get all the metals of the 

 iron group plus such other metals as cadmium, manganese, 

 titanium, barium, and so on. The solar atmosphere, then, from 

 top to bottom, consisted, it was imagined, of a series of shells, 



