In 1830, however, it was found desirable to send an expedition to the North-west, with a view to restoring peace between the Chippeways and Sioux; and the leader selected――the Schoolcraft who had been mainly instrumental in organizing the trip made a few years previously by Cass――received instructions to combine with his negotiations an exhaustive survey of the upper waters of the Mississippi. He reached Lake Superior in safety in 1830, but the waters of the rivers above it were so low at that time that nothing definite could be accomplished. Two years later, Schoolcraft started again, and, after a successful voyage up the great river, he arrived at Cass Lake, the most northerly point reached by the predecessor who had given his name to that now famous sheet of water. Here the real difficulties of the expedition began. The Mississippi branched out into two forks, one of which――the eastern――was followed to its source in Lake Ussawa, whence an arduous tramp, or rather paddle, across country brought the party, first to the lofty ridge known as the Hauteur des Ferres, separating the tributaries of the River de Corbeau from those of the Red River, and then in sight of the western and main branch of the Father of Waters. A number of sandy elevations had still to be scaled before the explorers once more stood upon the shores of the Mississippi, but on issuing from “a thicket into a small weedy opening,” the goal of the journey suddenly burst upon them. Itasca Lake, the primal home of the western branch of the mighty river, lay stretched before them, and the last link in the chain of discovery connected with the longest water highway in the world was found. Itasca Lake, the Lac la Biche of the early French explorers, is a beautiful sheet of water some seven or eight miles in circumference, with an outlet about twelve feet wide, whence the Mississippi expands into a broad and copious stream. Its volume appeared strangely out of proportion to the size of its source, till the presence of invisible subterranean springs, such as those near the African Lake Tanganyika, was ascertained. A thorough exploration of Lake Itasca was succeeded by a perilous voyage down a series of rapids forming the first stage of the Mississippi’s journey to the ocean; but, after many a narrow escape, the canoes floated into the broad stream, flanked on either side by prairies, into which the river widens above Lake Cass, whence the trip to Lake Superior lay through districts already well known. CHAPTER XIV. DISCOVERY OF THE GREAT BASIN, WITH THE SALT LAKE OF UTAH, AND JOURNEY ACROSS THE SIERRA NEVADA TO CALIFORNIA.