Twenty years ago S. F. Emmons, in a presidential address before the Geological Society of Washington, divided the history of Governmental surveys in this country into two periods, separated in a general way by the Civil War. The first of these was the period of geographic exploration, the second that of geologic exploration. Mr. Emmons of course regarded this subdivision as not hard and fast, yet his dividing line seems logical, for not only did the military activities in the East necessarily suspend exploration in the West, but after the war national, political, and economic considerations led naturally to the demand for a more exact knowledge of the vast national domain in the West. Geography and geology are so closely related that Mr. Emmons’s distinction of the two periods is useful only with the limitations inferentially set by himself—namely, that while geologic investigation entered into most of the explorations of the earlier period, the geologist was regarded as only an accessory in these exploring expeditions; on the other hand, in the later surveys the topographic work was developed because it was essential to the geologic investigations. The year 1818 was a notable one in American geology, first of all in the appearance of the American Journal of Science, itself so perfect a vehicle for geological thought that, as is so well stated by Dr. G. P. Merrill, “a perusal of the numbers from the date of issue down to the present time will alone afford a fair idea of the gradual progress of American geology.” The beginning of publications on New England geology appeared that year in Edward Hitchcock’s first paper on the Connecticut Valley (1, 105, 1818) and the Danas’ (S. L. and J. F.) detailed geologic and mineralogic description of Boston and vicinity; and the “Index” of Amos Eaton (noticed in this Journal, =1=, 69) was the first of that long list of notable contributions to American stratigraphy that are to be credited to the New York geologists. In the present discussion, too, the year 1918 can be regarded as in a way the centennial of Government geologic surveys, for it was in 1818 that Henry R. Schoolcraft began his trip to the Mississippi Valley—perhaps the first geologic reconnaissance into the West—and it was his work in the lead region which served to make him a member of the Cass expedition sent out by the Secretary of War in 1820 to examine the metallic wealth of the Lake Superior region. The earlier Government explorations of Lewis and Clark, in 1803–7, and of Pike, in 1805–7, were so exclusively geographic that geologic work under Federal auspices must be regarded as beginning with Schoolcraft and with Edwin James, the geologist of the expedition of Major Long in 1819–20 to the Rocky Mountains. Both these observers published reports that are valuable as contributions to the knowledge of littleknown regions.