THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[THIRD SERIES.] 



FEBRUARY 1847. 



XVI. The Astronomer Royal on Sir David Brewster's 

 Neiso Analysis of Solar Light. 



To the Editors of the Philosophical Magazine a7id Jotirnal. 



Gentlemen, 



Royal Observatory, Greenwich, Jan. 15, 1847. 

 f N the Notes to the second edition of the History of the 

 ■*■ Inductive Sciences, Dr. Whewell has (with my consent) 

 referred to experiments, made by me and described by me at 

 a meeting of the Cambridge Philosophical Society, tending to 

 invalidate the conclusions drawn by Sir David Brewster in a 

 paper headed " On a New Analysis of Solar Light, indicating 

 three Primary Colours, forming Coincident Spectra of equal 

 length," which is printed in the twelfth volume of the Edin- 

 burgh Transactions. I think it therefore incumbent on me 

 to give to the public the best account that I am now able to 

 give of these experiments. The reason of the partial imper- 

 fection of the account is the following. 1 never drew up in 

 writing any orderly statement either of the experiments or of 

 the reasoning connected with them. I had the pencil notes, 

 written each at the instant of making an experiment ; and from 

 these notes, or rather from the strong recollection of every 

 experiment detailed in the notes, I made my oral statement 

 (as far as the mere experimental facts were concerned) to the 

 Cambridge Philosophical Society. These notes I have mis- 

 laid^ and in consequence I am unable to give details on the 

 names and combinations of the different absorbing substances 

 which I employed. But upon the method, upon the results, 

 and upon the reasonings, my recollection is as perfect as it 

 was on the days on which the experiments were made. Ha- 

 ving j)remised this, I shall give my statement in the same order 

 in which I gave it (in the year 1833, I believe) to the Cam- 

 bridge Philosophical Society. 



/-•////. Mag. S. 3. Vol. 30. No. 199. Feb. 18 17. G 



