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Monday, 19th March 1855. 

 COLONKL MADDEN, Councillor, in the Chair. 

 The following Communications were read : — 



1. Experiments on Colour as perceived by the Eye, with Re- 

 marks on Colour-Blindness. By James Clerk Maxwell. 

 Esq., B.A., Trinity College, Cambridge. Communicated 

 by Professor Gregory. 



These experiments were made with the view of ascertaining and 

 registering the judgments of the eye with respect to colours, and 

 then, by a comparison of the results with each other, by means of a 

 graphical construction, testing the accuracy of that theory of the 

 vision of coloui- which analyses the colour-sensation into three ele- 

 ments, while it recognises no such triple division in the nature of 

 light, before it reaches the eye. 



The method of experimenting consisted in placing before the eye 

 of the observer two tints, produced by the rapid rotation of a system 

 of discs of coloured paper, arranged so that the proportions of each 

 of the component colours could be changed at pleasure. The ap- 

 paratus used was a simple top, consisting of a circular plate on 

 which the coloured discs were placed, and a vertical axis. The 

 discs consisted of paper painted with the unmixed colours used in 

 the arts. Each disc was slit along a radius from centre to circum- 

 ference, so that several could be interlaced, so as to leave exposed a 

 sector of each. The larger discs, about 3 inches diameter, were 

 first combined and placed on the disc, and the smaller, about If 

 inches diameter above them, so as to leave a broad ring of the 

 larger discs visible. 



When the top was spun the observer could compare the resulting 

 tint of the outer and inner circles, and by repeated adjustment, per- 

 fect identity of colour could be obtained. The proportions of each 

 colour were then ascertained, by reading off on the circumference of 

 the top, which was divided into 100 parts. As an example, it was 

 found on one occasion, that, — 



