Louis, a little to the south of the junction of the Missouri and the Mississipi, to the mouth of the latter river at Old French Balize, it has only a fall of 357 (380 English) feet in an itinerary distance of more than 1280 geographical miles. The surface of Lake Superior is 580 (618 English) feet above the level of the sea, and its depth near Magdalen Island is 742 (791 English) feet; its bottom, therefore, is 162 (173 English) feet below the surface of the ocean. (Nicollet, p. 99, 125, and 128.) Beltrami, who separated himself from Major Long’s expedition in 1825, boasted of having discovered the source of the Mississipi in Lake Cass. The river in the upper part of its course passes through four lakes, of which Lake Cass is the second. The uppermost is the Istaca Lake (in lat. 47° 13′ and long. 95° 0′), and was first recognised as the true source of the Mississipi in the expedition of Schoolcraft and Allen in 1832. This afterwards mighty river is only 17 feet wide and 15 inches deep when it issues from the singular horse-shoe-shaped Lake of Istaca. It was not until the scientific expedition of Nicollet, in 1836, that a clear knowledge of the localities was obtained and rendered definite by astronomically determined positions. The height of the sources of the Mississipi, viz. of the remotest affluent received by the Lake of Istaca from the dividing ridge or “Hauteur de Terre,” is 1575 (1680 English) feet above the level of the sea. In the immediate vicinity, and indeed on the southern slope of the same dividing ridge, is Elbow Lake, in which the smaller Red River of the North, which after many windings flows into Hudson’s Bay, has its origin. The Carpathian mountains present similar circumstances in the proximity and relative positions of the sources of rivers which send their waters respectively to the Black Sea and to the Baltic. Twenty small lakes, forming narrow groups to the south and west of Lake Istaca, have received from M. Nicollet the names of distinguished European astronomers, adversaries as well as friends. The map thus becomes a kind of geographical album, reminding one of the botanical album of Ruiz and Pavon’s Flora Peruviana, in which the names of new genera of plants were adapted to the Court Calendar, and to the various changes taking place in the Oficiales de la Secretaria.