A PHOTOGRAPH IN NATURAL COLOURS. 
47 
ingenious, simple, and capable of producing good results. In 
the Woodbury process, the lights and shadows are formed of 
transparent-coloured gelatine in various degrees of thickness, 
the deepest shadows being composed of the greatest thickness 
of the gelatinous ink. If a picture of this kind be printed 
upon a sheet of white paper, it will be in monochrome ; but it 
occurred to Mr. Ashton to try the effect of producing flat tints 
by means of chromo-lithography on paper, and upon this 
printing the Woodbury picture in correct registration with 
those tints. This, in principle, is totally different from the 
colouring of a photograph by applying pigments upon it ; for, 
in this latter, every touch of pigment hides some portion of 
the sun picture, whereas in the former the photograph is left 
quite intact ; thus nature can be imitated with a wonderful 
degree of exactness, the most delicate details of the photo- 
graph being harmoniously wedded to colours possessing all the 
vigour of the artist’s pigments. To produce by this process a 
thousand or more photographs, the services of a skilled artist 
are required only to arrange the colours on the various litho- 
graphic stones, and when this is done the production of the 
chromo-lithographic print which is to act as the substratum for 
the photograph, as well as the photograph itself, is a mere 
mechanical task, requiring technical care, but no artistic skill. 
It is anticipated that the application of colour in this way to 
Woodbury prints will be extensively carried out during th§ 
year now begun. 
At the last meeting of the British Association much interest 
was manifested in a new process of photo-polychromy which 
was described, and specimens exhibited on behalf of M. Leon 
Vidal, of Marseilles, the inventor of the process. It is based upon 
the carbon or pigment printing process, but resembles in principle 
chromo-lithography. Every different tint that is shown in the 
picture implies a separate print, the colouring matter of which 
is set off or transferred to the sheet upon which the finished 
picture is finally impressed. As many negatives must be em- 
ployed as there are colours to be printed. For example, sup- 
pose that the subject to be photographed were a web of tartan 
composed of three colours — red, blue, and yellow ; three nega- 
tives would have to be taken, and from the first every part 
except that which is to be printed red would be stopped out 
with opaque varnish, and the same in respect of the other two. 
Three sheets of pigmented sensitive paper, one being of each 
of the colours required, are now printed by the ordinary process 
of photography, the red pigmented paper being printed by the 
corresponding negative, and the same with the yellow and blue 
colours. Each picture when finished has only a portion of the 
pattern impressed upon it. But the paper is thin and trans- 
