VOL. 4, No. 2
PHOTOORAPHY FOR SCIENTIFIC W ORK
213
film or plate is partially effe~tive,"~ but the most uniform results are secured by developing in a flat tray with the film or plate completely immersed and gently brushing the surface of the emulsion with a wide camel hair brush. All emulsions should he handled by light to which they are relatively insensitive, otherwise fog will be prod~ced."~The choice of a safelight depends upon the sensitivity of both the eye and the emulsion to the light which the safelight transmits. It is possible to examine high-speed emulsions in yellow light which are normally fogged by such a light by treating them before development in a solution of a desensitizer173 which lowers the sensitiveness of the unexposed emulsion but does not affect the latent image. Panchromatic emulsions are not as responsive to desensitizers as ordinary emulsions hut they may be desensitized sufficiently to allow ready inspection during processing. The speed and color sensitivity of panchromatic emulsions may be increased by hypersensitizing with ammonia.'T4 For developing and fixing the manufacturers' instructions should be carefully followed. Full details for the development of motion-picture film have been given by one of the author^."^ The illustrations included with the paper have been added to show examples of several kinds of photographic records. For information relating to several different types of ph6tograpbic recording apparatus and the loan of photographs, the authors wish to acknowledge their indebtedness to W. R. Amberson, University of Pennsylvania, Philadelphia, Pa.; W. G. France, Ohio State University, Columbus, 0.; Dr. John J. Fiigan, Genesee Hospital, Rochester, N. Y.; L. M. Griffith, National Advisory Committee of Aeronautics, Langley Field, Hampton, Va.; P. E. Klopsteg, Central Scientific Co., Chicago, Ill.; Anna I,. MacLeod, Vassar College, Poughkeepsie, N. Y.; and F. H. Norton, Massachusetts Institute of Technology, Cambridge, Mass. Sheppard, at el., J. Frank. Inst., 195, 211 (1923);Ibid., 198, 333 (1924). Dundon and Crabtree, Am. Phot., 20,378,438 (1926). ""urka, I. Frank. Inst., 189, 25 (1920); also "Eastman Panchromatic Negative Film for Motion Pictures," Eastman Kodak Co., Rochester, N. Y., p. 8. lT5 Crabtree, Trans. Soc. Motion Picture Eng., 16, 163 (1923).
Chromium Used in Auto Manufacture. Chromium, once a chemical curiosity, is now being used in the automotive industry on account of its hardness and resistance to corrosion. W. N. Phillips of the General Motors Corporation reported to the Society of Automotive Engineers meeting in Detroit recently, that chromium plated upon steel and other metals is being used for coating gages, tools, dies and files, finishing radiators, and surfacing bearing surfaces. Chromium has been found to be harder than the hardest steels used in automobile manufacture.-ScienceService
