288 Mr. Charles Tomlinson on 



But, after studying the phenomena, he found the same 

 principles equally available, even so much so, that they 

 embraced all that is true, both in the theory of Nevi^ton 

 and that of Huygens, for they include the undulatory 

 theory when stripped of its redundancies and deficiencies. 

 In consequence of this, the author published his ** Physical 

 Optics," — only a fevr copies of these works remain in the 

 author's hands. When they were published, he was not 

 in possession of the demonstrations contained in this paper. 

 He submits, in a special manner, that of the 2nd prop, to 

 the notice of the mathematician ; if this maintain its 

 ground, the theory cannot be shaken. The author is per- 

 suaded that it is impregnable. The present application of 

 the principles to chemistry is a farther confirmation of its 

 truth, if such were needed ; for in this short paper impor- 

 tant phenomena are clearly explained, which the combined 

 efforts of all the philosophers of Europe, during the last 

 and the present century, have not been able to solve or 

 unfold. Thomas Exley. 



Bristol, September 7th, 1836. 



Article IV. 



A Theory of Accidental and Complementary Colours. 



By Charles Tomlinson, Esq. 



{Concluded from p. 217.) 



ON COLOURED SHADOWS. 



17. Dr. Thomas Young, in his lectures on Natural 

 Philosophy, vol. i., p. 456, states that " when the shadows 

 of objects are placed in coloured light, the shadow appears 

 of a colour opposite to that of the stronger light, even 

 when it is in reality illuminated by a fainter light of the 

 same colour." This he explains on the assumption that 

 the eye cannot perfectly distinguish the intensity of a 

 colour, either when the light is extremely faint or exces- 

 sively vivid. This explanation, if such it be, I cannot 

 adopt ; because, I think it entirely inadequate to account 

 for the phenomena of coloured shadows. 



18. Independently of the theory of coloured shadows, 

 there is an important principle established by their investi- 

 gation, and admitted by Dr. Young, viz., that every shadow 



