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Draper, John William

draper’s scientific photography chemical

(1811–82) British–US chemical physicist: a pioneer of scientific photography.

Draper’s life and his scientific interests were both oddly disperse. His father was an itinerant Methodist preacher whose possession of a telescope attracted the boy to science. He began premedical studies in London in 1829 but emigrated to Virginia in 1832. Helped by his sister Dorothy’s earnings as a teacher, he qualified in medicine by 1836 and then taught chemistry in New York. When process for fixing photographs was published in 1839, Draper took it up and in 1840 he made what is probably the oldest surviving photographic portrait; it shows his sister Dorothy (exposure, 65 s). In the same year his photograph of the Moon began astronomical photography and in 1850 he made the first microphotographs, to illustrate his book on physiology. In 1841 he proposed the principle that only absorbed radiation can produce chemical change (Draper’s Law; this principle was also known to T C J D Grotthus (1785–1822) in 1817). He made early photographs in the infrared and ultra-violet regions; and he showed that all solids become incandescent at the same temperature and, when heated sufficiently, give a continuous spectrum. His later work was on the history of ideas.

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