THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



MARCH 1847. 



XXVIII. Reply to the Astronomer Royal o« the New Analysis 

 of Sola)- Light. By Sir David Brewster, K.H,, D.C.L., 

 F.R.S. and V.P.R.S. Edin.* 



THE remarks of Mr. Airy in the last Number of this 

 Journal, on my Analysis of the Solar Spectrum, have, I 

 doubt not, given as much surprise to its scientific readers as 

 they have given to me, and this independently of the correct- 

 ness or incorrectness of the results to which they refer. When a 

 philosopher examines, and pronounces an opinion upon the re- 

 searches of others, especially upon those which competentjudges 

 have recognised as sound, he is bound to repeat the identical ex- 

 periments which hechalienges, with similar apparatus and similar 

 materials ; to state the differences which he observes, to inquire 

 into the causes by which such discrepancies have arisen, to 

 establish his own views by new and effective experiments, and 

 to publish his researches in vindication of his charges against 

 a fellow-labourer in science. Mr. Airy, however, has not 

 done this; but, as we shall presently see, has followed a course 

 which is as unusual in the history of science as it may be in- 

 jurious to its progress. 



The question (the only one as Mr. Airy says) to which 

 these observations bear reference is this : " Is it established 

 that the colour of any porlioji of the spectrum is changed by the 

 use of any absorbing medium ?" To this question I and others 

 have given the answer, that absorbing media do change the 

 colour of different portions of the spectrum, I give the same 

 answer still ; and rather than believe that I have been blind 

 for the \si^\. fifty years, I will hazard the supjjosition that the 

 Astronomer Royal cannot distinguish colours, and is a genuine 

 specimen of an idiopt, the name which his friend Dr. WhevvcU 



* Communicated by the Author. 

 Phil. Mag. S. 3. Vol. 30. No. 200. March 1 847. M 



