526 Sir DAVID BREWSTER on the Lines of the Solar Spectrum, 



ones in the solar spectrum, yet, in many cases, faint and narrow 

 lines in the one coincided with strong and broad lines in the 

 other ; and there were some strong gaseous lines, and even broad 

 bands, to which I could discover no counterpart in FRAUNHOFER'S 

 map of the spectrum, which, at this stage of my inquiry, was the 

 standard to which I appealed. This discrepancy at first embar- 

 rassed me, and, as I observed it in parts of the spectrum where 

 FRAUNHOFER had laid down every line which he had seen with 

 his finest instruments, I abandoned all hopes of being able to es- 

 tablish the general principle of their identity. I was therefore 

 obliged either to renounce this principle as one contradicted, or 

 rather not confirmed by observation, or to consider FRAUNHOFER'S 

 delineation as in fault, and to enter upon the Herculean task of 

 making a better map of the spectrum. 



The magnificence of FRAUNHOFER'S instruments, the means 

 of nice observation which he had at his command, and his great 

 skill as an observer, were considerations which long deterred me 

 from even attempting to repeat his examination of the spectrum. 

 Possessing such inferior means, and situated in so unfavourable 

 a climate, I should have felt the attempt as presumptuous ; but in 

 the comparison which I had already made of the gaseous and so- 

 lar lines, I had detected grave errors, and inexplicable omissions, 

 in FRAUNHOFER'S map, and was disposed even to adopt the sug- 

 gestion of Mr H. F. TALBOT, (to whom I mentioned the fact, and 

 who had the same confidence that I had in FRAUNHOFER'S ac- 

 curacy) that a change might have taken place in the light of the 

 sun itself, and that the delineation of the Bavarian philosopher 

 might have been perfectly accurate at the time when it was exe- 

 cuted. This supposition, however, became less and less tenable 

 as I proceeded in the identification of the two classes of lines ; 

 but even if it had been otherwise, it would have added a still 

 more powerful motive, while it afforded the best apology for un- 

 dertaking a new delineation of the spectrum. 



The apparatus which I had at my command for this investi- 



