VY: 
ON A METHOD OF PHOTOGRAPHY IN NATURAL COLOURS. 
By J. JOLY, M-A., Sc.D, E.R:S: 
(Praces VY. ann, Vi.) 
(Read June 26, 1895.) 
In 1861 Clerk Maxwell read a Paper before the Royal Institution of Great 
Britain, ‘‘ On the Theory of Three Primary Colours.’’* 
In this Paper he announced very briefly his discovery of a method whereby the 
colours of nature could be photographically reproduced by the superposition by 
optical projection of three coloured images. How far the method then described 
by Maxwell embodies the theory and practice of recent efforts in this direction 
must be judged from his own words. 
After displaying upon the screen the three primary colours by passing a beam 
of white light through three suitably coloured solutions he proceeds to show the 
synthesis of the spectrum by projection : ‘The graduated intensity of the primary 
colours in different parts of the spectrum was exhibited by three coloured images, 
which when superposed on the screen gave an artificial representation of the 
spectrum.” Then follows :— 
“Three photographs of a coloured ribbon taken through the three coloured 
solutions respectively were introduced into the camera, giving images representing 
the red, the green, and the blue parts separately as they would be seen by each of 
Young’s three sets of nerves separately. When these were superposed a coloured 
image was seen which, if the red and green images had been as fully photographed 
as the blue, would have been a truly coloured image of the ribbon. By finding 
photographic materials more sensitive to the less refrangible rays, the represen- 
tation of the colours of objects might be greatly improved.” 
In this description not only is the method of colour synthesis by triple 
projection described, but in the words defining the mode in which the three 
photographic images are to be secured, ‘‘as they would be seen by each of 
Young’s three sets of nerves separately,” the complete theory of composite colour 
* Collected Papers, vol. i., p. 449. 
TRANS. ROY. DUB. SOC. N.S. VOL. VI., PART V, x 
