THE 



LONDON and EDINBURGH 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



♦ 



[THIRD SERIES.] 

 DECEMBER 1833. 



LXIII. On the Absorption of Light by Coloured Media, viewed 

 in connexion with the Undulaiory Theory. By Sir John F. 

 W. Herschel, K.H* 



nPHE absorption of light by coloured media is a branch of 

 ■*• physical optics which has only since a comparatively recent 

 epoch been studied with that degree of attention which its im- 

 portance merits. The speculations of Newton on the colours 

 of natural bodies, however ingenious and elegant, can hardly, 

 in the present state of our knowledge, be regarded as more 

 than a premature generalization ; and they have had the na- 

 tural effect of such generalizations, when specious in them- 

 selves and supported by a weight of authority admitting for 

 the time of no appeal, in repressing curiosity, by rendering 

 further inquiry apparent!} 7 superfluous, and turning attention 

 into unproductive channels. I have shown, I think satisfac- 

 torily, however, in my Essay on Light, that the applica- 

 bility of the analogy of the colours of thin plates to those of 

 natural bodies is limited to a comparatively narrow range, 

 while the pheenomena of absorption, to which I consider the 

 great majority of natural colours to be referrible, have always 

 appeared to me to constitute a branch of photology sui generis 

 to be studied in itself by the way of inductive inquiry, and by 

 constant reference to facts as nature offers them. 



The most remarkable feature in this class of facts consists 

 in the unequal absorbability of the several prismatic rays, and 

 the total abandonment of anything like regularity of progress 



* Communicated by the Author. The substance of this paper was read 

 before the Section of Physics of the British Association, at Cambridge. 



Third Series. Vol. 3. No. 18. Dec. 1833. 3 F 



