SCIENCE IN THE INDUSTRIAL WORLD 



spread a gelatine-bromide emulsion sensitive to all 

 colors. Thus we have a complete outfit photo- 

 graphic plate and color screen in one. In exposing 

 this plate in the camera the glass side is placed towards 

 the lens, and the light consequently has to pass through 

 the granular colored layer before reaching the gelatine 

 film. The resulting negative is developed but not 

 fixed, and the reduced silver is dissolved by means of 

 the acid permanganate of potassium process. The 

 plate is then transformed from a negative to a posi- 

 tive, and each colored particle lets the light pass which 

 is necessary to produce that special shade. When held 

 up to the light the plate shows the color as well as the 

 shape of the photographic subject. 



The ease of manipulation and excellent results of 

 the Lumiere autochrome plates have turned inventive 

 effort largely to the methods used in their manufacture. 

 Already a new plate known as the "omnicolor" has 

 been produced. This, however, goes back to the old 

 idea of the geometrical plate and is prepared by "treat- 

 ing a gelatine film (upon a glass plate) successively 

 with certain reserves, coloring matters, and varnishes, 

 thus producing a kind of mosaic of red and green 

 rectangles, and blue lines. The red and green fields 

 are quite regular in form; the blue lines, on the other 

 hand, show constrictions at constant intervals, cor- 

 responding to their intersections with the red fields. 

 As a matter of fact this red color is distributed in nar- 

 row red bands, and the blue lines superposed upon 

 these produce at the point of contact a purplish violet 

 color." These plates are used precisely as the auto- 



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