Here he conducted experiments and published eight papers before entering medical school. His sister Dorothy Catherine Draper provided finances through teaching drawing and painting for his medical education. In March 1836, he graduated from the University of Pennsylvania School of Medicine. That same year, he began teaching at Hampden–Sydney College in Virginia. New York In 1837, Draper accepted an appointment to be head of chemistry in a proposed medical school at New York University, but sufficient funds were not available to go ahead with the project. In 1839, Draper was elected undergraduate professor of chemistry and botany at the university, and moved with his family to New York City . Once there he helped to found the New York University Medical School, acting as a professor there from 1840 to 1850, president of the school from 1850 to 1873, and as a professor of chemistry until 1881. Work Draper did important research in photochemistry, made portrait photography possible by his improvements (1839) on Louis Daguerre's process, and published a textbook on Chemistry (1846), textbook on Natural Philosophy (1847), textbook on Physiology (1866), and Scientific Memoirs (1878) on radiant energy. In 1839–1840, Draper produced clear photographs which at that time were regarded as the first life photographs of a human face. Draper took a series of pictures, with a 65-second exposure in sunlight. The first ones, of a female assistant whose face was covered with a thin layer of flour to increase contrast, were not preserved. Draper also photographed his sister, Dorothy Catherine Draper, and one of those pictures (see image) became known to the public via the letter which Draper sent to John Herschel in 1840. Several copies were made of this picture in the 19th century, and the photograph attached with Draper's letter was also likely a copy made by Draper himself. In March 1840 Draper became the second person to produce photographs of an astronomical object, the Moon, considered the first astrophotographs. In 1843 he made daguerreotypes of the solar spectrum that revealed new infra-red and ultra violet lines. In 1850 he was making photomicrographs and engaged his son, Henry (then 13 years old), into their production. Draper developed the proposition in 1842 that only light rays that are absorbed can produce chemical change. It came to be known as the Grotthuss–Draper law when his name was teamed with a prior but apparently unknown promulgator Theodor Grotthuss of