of Science,’ the ‘Journal of the Franklin Institute,’ and the ‘Philosophical Magazine.’ His principal papers were devoted to investigations concerning the phenomena of light and heat, and these their author collected and republished in one volume in 1878 under the title of ‘Scientific Memoirs, being experimental contributions to a Knowledge of Radiant Energy.’ In 1835 he published accurate experiments showing that Mrs. Somerville and others were incorrect in their supposition that steel can be magnetised by exposure to violet light. In 1837 he commenced a series of researches upon the nature of the rays of light in the spectrum. Using the then little-known spectroscope, Draper showed first that all solids become self-luminous at a temperature of 977° F., and that they then yield a continuous spectrum; and that as the temperature of the body rises it emits more refrangible rays, the intensity of the rays previously emitted also increasing. In 1843 Draper photographed the dark lines in the solar spectrum, and in 1857 he showed the superiority of diffraction over prismatic spectra. He devoted special energy to the study of the ultra-violet, or, as he styled them, tithonic rays, showing the presence of absorptive bands in them, as well as in the ultra-red rays. His latest papers—‘ On the Distribution of Heat and of Chemical Force in the Spectrum’—which appeared in the ‘Philosophical Magazine’ for 1872, may be considered as a summary of his views on the subject. His conclusions that ‘every radiation can produce some specific effect,’ and that it is a misnomer to limit the term of ‘chemical rays’ to those at the violet end of the spectrum, for ‘we must consider the nature of the substance acted upon as well was the light,’ are now generally accepted.
In 1839 Draper obtained portraits, for the first time, by the daguerreotype process. Early in 1840 Draper succeeded in taking the first photograph of the moon; ‘the time occupied was twenty minutes, and the size of the figure about one inch in diameter.’ In 1851 he secured phosphorescent images of the moon. To measure the chemical intensity of light Draper devised in 1843 a chlor-hydrogen photometer, an instrument which was subsequently perfected and employed by Bunsen and Roscoe. Draper was among the first, if not the first, to obtain photographs of microscopic objects by combining the camera with the microscope. He used daguerreotypes obtained in this way to illustrate his lectures on physiology given at the university of New York between 1845 and 1850. Draper applied his studies on capillary attraction to explain the motion of the sap in plants, and between 1834 and 1856 he published several papers upon this and kindred subjects, including the passage of gases through liquids, the circulation of the blood, &c. In 1844 and 1845 Draper carefully studied the elementary body chlorine, showing that it existed in two states—active and passive—and examining the action of light upon it and its compound with silver (silver chloride). The action of light upon plants formed the subject of another research (1843), and Draper showed that it was the yellow rays which were chiefly instrumental in the production of chlorophyll. Besides these detached ‘Memoirs,’ Draper wrote two valued text-books of science, a ‘Text-book of Chemistry’ (1846), and a ‘Human Physiology’ (1856), each of which passed through several editions. In 1875 the American Academy of Arts and Sciences gave Draper the Rumford medal for his ‘Researches in Radiant Energy,’ the president justly declaring him to have taken ‘a prominent rank in the advance of science throughout the world.’ Draper was led, as he declares, by his physiological studies, to apply to nations the same laws of growth and development, presenting the results in his ‘History of the Intellectual Development of Europe’ (1862), a book which has been translated into many languages. Another work which has been highly praised for its impartiality and philosophical elevation is Draper's ‘History of the American Civil War,’ published 1867–70. In 1874 Draper wrote the ‘History of the Conflict between Science and Religion,’ to which Professor Tyndall wrote the preface. By many Draper has been regarded as a materialist, but he was a theist and a firm believer in a future state. In the Royal Society's ‘Catalogue of Scientific Papers’ Draper's name is appended to fifty-one, besides three written in conjunction with W. M. Higgins.
[American Journal of Science, February 1882; Scientific American (with portrait), 14 Jan. 1882; Nature, 19 Jan. 1882; Report of the Rumford Committee of the American Academy of Arts and Sciences, 1876.]
DRAPER, Sir WILLIAM (1721–1787), lieutenant-general, was born in 1721 at Bristol, where his father, Ingleby Draper, was an officer of customs. According to Granger, his grandfather was William Draper of Beswick, near Beverley, a famous Yorkshire fox-hunting squire, noticed in ‘Biog. Hist.’ iii. 239. His uncle, Charles Draper, was a captain of dragoons (Gent. Mag. lxiv. (ii.) 869). He was sent to Bristol grammar school under Mr. Bryant, and was afterwards at
