218 THE CHEMISTRY OF THE SUN. [CHAP. 



still more, as I wished to find the dernier mot in the present 

 state of science regarding the coincidence of metallic with 

 Fraunhofer lines ; and for this it was imperative to work on 

 a large scale over a small region, rather than on a small scale 

 over a large one. 



In point of fact, this special work was limited to about 

 the T J^th part of the spectrum, and this was mapped on a 

 large scale. A complete map of the spectrum on the scale 

 adopted would be about half a furlong long. The work took 

 time : including interruptions of one kind and another, some 

 four years were expended on it. 



Finally, we had a large number of photographs which we 

 could study at our leisure, showing the physical characteristics 

 of the various lines of the different chemical elements and the 

 variations which the lines underwent under different conditions. 

 These were precious records, the many riddles of which are not 

 all, even yet, I think, read. We will take these various matters 

 seriatim. 



3. New Metals in the Sun. 



On page 156 I gave an account of the attempt made to 

 determine the existence of additional metals in the sun 

 by using the existing maps and tables in the absence of 

 precise knowledge touching the longest lines. The photo- 

 graphs now came to the aid of the eye observations which 

 had been made on the new method of the spectra of lithium, 

 sodium, magnesium, cobalt, nickel, aluminium, lead, manganese, 

 cadmium, tin, zinc, strontium, antimony, and barium. 1 



In the case of these metals we now had the longest lines 

 from red to violet, and the photographs gave us the longest 

 lines in the violet and blue of the other substances, the less 

 refrangible portions of the spectra of these latter had not been 

 mapped on the new method. 



1 Phil. Trans. 1873, p. 253. 



