An account of the sugar maple-tree, of the United States, and of the methods of obtaining sugar from it : together with observations upon the advantages both public and private of this sugar. : In a letter to Thomas Jefferson, Esq. secretary of state of the United States, and one of the vice presidents of the American Philosophical Society. : Read in the American Philosophical Society, on the 19, of August, 1791, and extracted from the third volume of their Transactions now in the press. / By Benjamin Rush, M.D. Professor of the institutes and of clinical medicine in the University of Pennsylvania.