Louis, somewhat to the south of its confluence with the Missouri, the Mississippi has a fall of only 380 feet, notwithstanding that the itinerary distance between these two points exceeds 1280 miles. The surface of Lake Superior lies at an elevation of 618 feet, and as its depth in the neighbourhood of the island of Magdalena is fully 790 feet, its bottom must be 172 feet below the surface of the ocean.[Z] Beltrami, who in 1825 separated himself from Major Long’s expedition, boasted that he had found the sources of the Mississippi in Lake Cass. The river passes, in its upper course, through four lakes, the second of which is the one referred to, while the outermost one, Lake Istaca (47° 13′ north lat., and 95° west long.), was first recognised as the true source of the Mississippi, in 1832, in the expedition of Schoolcraft and Lieutenant Allen. This stream, which subsequently becomes so mighty, is only 17 feet in width, and 15 inches deep, when it issues from the singular horse-shoe-shaped Lake Istaca. The local relations of this river were first fully established on a basis of astronomical observations of position by the scientific expedition of Nicollet, in the year 1836. The height of the sources, that is to say, of the last access of water received by Lake Istaca from the ridge of separation, called _Hauteur de Terre_, is 1680 feet above the level of the sea. Near this point, and at the southern declivity of the same separating ridge, lies Elbow Lake, the source of the small Red River of the north, which empties itself, after many windings, into Hudson’s Bay. The Carpathian Mountains exhibit similar relations in reference to the origin of the rivers which empty themselves into the Baltic and the Black Sea. M. Nicollet gave the names of celebrated astronomers, opponents as well as friends, with whom he had become acquainted in Europe, to the twenty small lakes which combine together to form narrow groups in the southern and western regions of Lake Istaca. His atlas is thus converted into a geographical album, reminding one of the botanical album of the _Flora Peruviana_ of Ruiz and Pavon, in which the names of new families of plants were made to accord with the Court Calendar, and the various alterations made in the _Oficiales de la Secretaria_.