Somewhat shorter than the visible rays of light are the ultra-violet rays which, through the microscope, Feveal the' detailed structure of minute objects which pass _unob-Served when examined by
photography, the examiner of ques-Higo With the ald of, ultraviolet Hloned documents becomes the despair of the forger, for he is enabled to Getect. the smallest changes and to fay bare the falsifications of the most careful of criminals. Ultra-violet fays have also enabled the historian decipher old documents, written fon parchment, the ink of which hat completely faded in the course of Within the past year or two scientists have succeeded in making photographic plates and films respond to {infra-red light with startling results. Mount Wilson Observatory has dis-the possibility of carbon-oxide gas inthe atmosphere of the planet Venus, a fact which suggests The possibility of life on that celestial body. Photographs have, been taken of groups of people in total darkness, and even flatirons have been. per-Sinded to take portraits "of themselves.
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