Several travelers of the eighteenth century, among them, especially, Guettard, Alexander, and Schoepf, gave more or less important information respecting the geological structure and mineral resources of our country; but geological work, properly so called, began only with Maclure’s studies in 1806. Born in Scotland, Maclure came to this country in early youth, and, embarking in business, acquired a fortune long before reaching middle age. He returned to Europe to spend several years in the study of natural science, but came again to America in 1806 to take up his geological work, which continued until 1808. The publication of his results, presented to the American Philosophical Society on January 20, 1809, led others to make studies, and soon afterwards there appeared numerous papers dealing with geological subjects. Professor Samuel L. Mitchell, a devoted follower of Werner, infused much of his enthusiasm into a group of youthful students in . . .