John Peter Lesley, an American geologist, born in Philadelphia, Sept. 17, 1819. He graduated at the university of Pensylvania in 1838, and from 1839 to 1841 was engaged on the geological survey of that state under Prof. Henry D. Rogers. In the autumn of 1841 he entered the theological seminary of Princeton, N. J., and in 1844 was licensed as a minister by the presbytery of Philadelphia. After a while he visited Europe for a year, and pursued his theological studies at Halle. On his return he labored for two years as a missionary among the German population of Pennsylvania, and in 1847 became pastor of a Congregational church in Milton, Mass. He married in 1849 Miss Susan Lyman of Northampton, and in 1851, his theological views being no longer in accordance with his ecclesiastical position, he left the pulpit and settled in Philadelphia, where he has since devoted himself to geology. He had in 1842 constructed the state geological map and sections for Pennsylvania, and in 1846-7 revised them, and prepared the drawings and a large part of the text of the subsequently published report oh the geology of that state. His work as a geologist has been more especially devoted to the coal formations of North America, and he is regarded as a chief authority in all questions connected therewith.

His " Manual of Coal and its Topography" (1856) is esteemed alike for its classification of the Appalachian coal strata, and for its illustrations of topographical geology. He was for several years secretary to the American iron association, and in 1859 published The Iron Manufacturers' Guide." He has also for many years been secretary and librarian of the American philosophical society. In 1865 he gave a series of lectures before the Lowell institute in Boston, since published under the title of " Man's Origin and Destiny as seen from the Platform of the Sciences" (1868), in which he has brought together the results of varied studies. A large number of his geological papers, relating chiefly to coal, iron, and petroleum, and various essays on philological and antiquarian subjects, will be found in the proceedings of the American philosophical society. In 1872 he was appointed professor of geology and dean of the faculty to the newly established scientific department of the university of Pennsylvania, and in 1874 chief geologist of Pennsylvania, under a new act providing for a complete geological resurvey of that state.