Edward Livingston Youmans, an American scientific writer, born at Coeymans, N. Y., June 3, 1821. In his childhood his parents settled in Saratoga. At the age of 13 he was attacked with ophthalmia, resulting in blindness for several years, from which he recovered with very obscure vision and constant liability to the recurrence of the disease. He studied elementary chemistry and physics with the aid of his sister, who experimented and read for him, while he wrote with a machine of his own contrivance. In 1851 he issued a chemical chart illustrating composition by colored diagrams, which was revised and enlarged in 1856. In 1852 he published the "Class Book of Chemistry " (revised ed., 1863; translated into Spanish, 1866), which he rewrote in 1875, on the basis of recent chemical doctrines. In 1853 appeared "Alcohol and the Constitution of Man;" and in 1855 "The Chemical Atlas," with text. In 1857 he published " The Handbook of Household Science," and in 1864 " The Correlation and Conservation of Forces," a compilation with an introduction.

In 1867 he printed "The Culture Demanded by Modern Life," a compilation with an introduction, and containing an original lecture on "The Scientific Study of Human Nature." He has pursued a course of medical study, and received the degree of M. D. from the university of Vermont, but has not practised. He has lectured extensively, and, in his courses on " The Chemistry of the Sunbeam" and "The Dynamics of Life," was the first to expound popularly the doctrines of the conservation of energy and the mutual relations of forces. In 1871 he planned the "International Scientific Series," and arranged for the publication of the works in New York, London, Paris, and Leipsic, the arrangement being subsequently extended to St. Petersburg and Milan. The project was based on the idea of payment to authors from the sale in all countries. Twenty volumes of the series have been issued (1876). In connection with this and similar undertakings he has made several visits to Europe. In 1872 he established the "Popular Science Monthly" in New York. Dr. Youmans has been instrumental in publishing the works of Herbert Spencer in this country, and he has also promoted the circulation here of the works of various foreign scientific writers, with the same remuneration to them that is allowed to American authors. - His sister, Eliza Anne Youmans, became interested in the scientific studies which she aided him to pursue, and her fondness for children led her to apply them to early education.

In 1870 she published the "First Book of Botany, designed to cultivate the Observing Powers of Children," and in 1873 the " Second Book of Botany." These are intended to promote the systematic study of plants as objects, in place of the loose and incoherent "object lessons" in general use. She has also prepared an enlarged edition of Henslow's "Botanical Charts" (1873), translated from the French Quatrefages's " Natural History of Man" (1875), and contributed to the " Popular Science Monthly " and other periodicals.