Draper , John William

Draper , John William
(1811–1882) British–American chemist
Draper, who was born in St. Helens, Lancashire, was educated at University College, London, before he emigrated to America in 1833. He qualified in medicine at the University of Pennsylvania in 1836. After a short period teaching in Virginia he moved to New York University (1838) where he taught chemistry and in 1841 helped to start the medical school of which he became president in 1850.
Most of his chemical work was done in the field of photochemistry. He was one of the first scientists to use Louis Daguerre's new invention (1837) of photography. He took the first photograph of the Moon in 1840 and in the same year took a photograph of his sister, Dorothy, which is the oldest surviving photographic study of the human face. In 1843 he obtained the first photographic plate of the solar spectrum. He was also one of the first to take photographs of specimens under a microscope. On the theoretical level Draper was one of the earliest to grasp that only those rays that are absorbed produce chemical change and that not all rays are equally powerful in their effect. He also, in a series of papers (1841–45), showed that the amount of chemical change is proportional to the intensity of the absorbed radiation multiplied by the time it has to act. Draper's work was continued and largely confirmed by the work of Robert Bunsen and Henry Roscoe in 1857. Draper's work also resulted in the development of actinometers (instruments to measure the intensity of light). He also wrote on a wide variety of other topics.
Draper's son Henry was an astronomer of note after whom the famous Harvard catalog of stellar spectra was named.

Scientists. . 2011.

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  • Draper, John William — (1811 1882)    Historian, b. at St. Helen s, Lancashire, emigrated to Virginia, and was a prof. in the Univ. of New York. He wrote History of the American Civil War (1867 70), History of the Intellectual Development of Europe (1863), and History… …   Short biographical dictionary of English literature

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