THOMAS, David, engineer, born in Montgomery county, Pennsylvania, in 1776; died in Cayuga county, New York, in 1859. He was of Quaker parentage. Removing to the vicinity of Aurora, Cayuga County, in 1805, he was appointed chief engineer of the Erie canal west of Rochester, and subsequently he became principal engineer of the Welland canal, Canada. He was distinguished as a florist and pomologist, and by his writings rendered great services to scientific agriculture. He contributed extensively to the "Genesee Farmer" and published "Travels in the West" (Auburn, 1819).--His son, John J., agriculturist, born near Aurora, Cayuga County, New York, 8 January, 1810, was almost entirely self-taught. He studied the botany of the neighborhood in boyhood, making an herbarium of 1,300 species, in 1834 became associate editor of the "Genesee Farmer" at Rochester, and when that journal was merged in 1853 in the " Country Gentleman," at Albany, he became connected with the latter, where he still continues (1888). He was horticultural editor of the " Albany Cultivator" in 1841-'53, contributed to the "Transactions" of the New York state agricultural society in 1841-'7, and to "The Farm" (New York, 1858), and edited the " Illustrated Annual Register of Rural Affairs" (9 vols., Albany, 1855-'81). He has published "The American Fruit Culturist" (Albany, 1845) ; " Farm Implements, and the Principles of their Construction and Use" (New York, 1854) ; and "Farm Implements and Farm Machinery" (1869). He received the degree of A. M. from Haverford college, Pennsylvania, in 1876. --Another son, Joseph, born in Cayuga county, New York, 23 September, 1811, was educated at Yale and at Rensselaer polytechnic institute, Troy, New York, and was graduated as a physician in Philadelphia, engaging in practice in that city. He was for some time professor of Latin and Greek in Haverford college, Pennsylvania, and also taught privately. In 1857 Dr. Thomas visited India, and spent fourteen months in the study of Sanscrit. Persian, and other oriental languages, and in 1858 he passed four months in Egypt in the study of Arabic. He has contributed to journals, and is the author of the system of pronouncing geographical names in "Baldwin's Pronouncing Gazetteer" (Philadelphia, 1845) ; the geographical and biographical vocabularies in several editions of Webster's Dictionary; and "Travels in Egypt and Palestine" (Philadelphia, 1853). With Thomas Baldwin he edited "A New and Complete Gazetteer of the United States" (1854) and " Lippincott's Pronouncing Gazetteer of the World " (1855), and he edited alone a "Comprehensive Medical Dictionary" (1864) and a " Universal Pronouncing Dictionary of Biography and Mythology " (2 vols., 1870-'1).