PHOTOGRAPHY, SCIENTIFIC ASPECTS 



color photography was being developed, efforts were 

 made to obtain a satisfactory method which would do 

 away with the necessity for these separate negatives 

 and the consequent optical lantern. 



"Forty years ago Ducos du Hauron suggested the 

 production of a screen-plate as forming a simple method 

 of color photography, which consists of a sheet of trans- 

 parent paper mechanically covered upon its surface 

 with three kinds of colored stripes or divisions. Writ- 

 ing of this method Du Hauron said: 'Let us imagine 

 that one covers the surface of the paper on the side 

 where the color stripes are imprinted with a prepara- 

 tion which gives, directly under the influence of light, 

 a positive proof, and that one receives on its reverse 

 side namely on the side not covered with stripes 

 the image of the camera. It will happen that the 

 three single colors will filter through the paper and form 

 each its positive print, that is, its print in light of the 

 corresponding ray of color, and the three prints 

 will be formed with the same rapidity, in spite of the 

 unequal degrees of actinism of the three simple colors, 

 if one has been careful to give each of these three sorts 

 of stripes a relative translucency, inversely as to 

 photogenic power of these same colors on the prepa- 

 ration employed.'" 



It is obvious that the colors must be distributed over 

 the proposed surface in quantities so minute that 

 when viewed by the eye they would be merged together 

 just as are the details of an engraving. Du Hauron 

 made his suggestion in 1868, but it was not until 1895 

 that the first screen-plate process was put forward 



VOL. VIH. 16 [ 241 ] 



