photoelectric

photoelectric-microscope, subst . A microscope illuminated by the electric light so that the image of the magnified body can be thrown on a screen in a darkened room. photo electrotype pho-to-a-lec-tro-type, subst . [Pref. photo- , and Eng. electrotype (q.v.).] A block made mainly with the aid of photography and of the electrotyping proce , and which can be printed with type like a woodcut. A photographic negative of the subject required is printed on a film of gelatine which has been treated with bichromate of potash, to render it sensitive to the action of light. Those parts on which the light has not acted are soluble in water, and are washed away, leaving the printed parts that are insoluble in relief. From this relief a mold in wax is taken, and an electrotype made in the usual way. Unle special means are taken to translate the half-tones of the photograph into line or stipple, this proce is only available for reproducing drawings, etc., in black and white.