TRANSACTIONS 
THE CROYDON MICROSCOPICAL AND 
NATURAL HISTORY CLUB. 
1899-1900. 
147.—TurEE-cotour PHoToGRAPHY APPLIED TO THE CoRRECT 
Deuineation or Natura History SusJects. 
By W. Savitue-Kenr, F.L.8., F.Z.8., &e. 
(Read March 20th, 1900.) 7 
Tue three-colour printing process as applied to the production 
of artistic and commercial illustrations is doubtless familiar to 
the majority of those present at this meeting; it having within 
the last few years made such substantial progress, that it 
promises within the next decade to completely outstrip and 
supersede the older and more elaborate system of chromo- 
lithography. 
In chromo-lithography a complex colour subject may require 
as many as twelve to sixteen or even twenty ponderous stones, 
each one specially engraved and supplied with its respective colour 
tint to produce in the combined print a correct replica of the 
original. Add to this, that each printing has to dry thoroughly 
before the application of the succeeding tint, such drying occupy- 
ing at least twenty-four hours, so that if we have only twelve 
colour stones to deal with, a fortnight is, at the shortest, occupied 
before the result is realised. 
The three-colour process, as its name implies, involves the 
~ employment of three colour-printings only, in conjunction with a 
proportionate abbreviation of the time occupied in its mechanical 
accomplishment. It is, moreover, an essentially photographic 
method; three separate negatives of diverse but scientifically 
gauged intensities being taken of each subject, and the combined 
c 
