+Note.+—All the varieties of this beautiful mineral, may at all times be seen in the +Indian Museum+; and by the curious, specimens may be obtained for any further experiments. LETTER—No. 56. ROCK ISLAND, _UPPER MISSISSIPPI_. It will be seen by this, that I am again wending my way towards home. Our neat little “dug out,” by the aid of our paddles, has at length brought my travelling companion and myself in safety to this place, where we found the river, the shores, and the plains contiguous, alive and vivid with plumes, with spears, and war-clubs of the yelling red men. We had heard that the whole nation of Sacs and Foxes were to meet Governor Dodge here in treaty at this time, and nerve was given liberally to our paddles, which had brought us from Traverse de Sioux, on the St. Peters river; and we reached here luckily in time to see the parades and forms of a savage community, transferring the rights and immunities of their natural soil, to the insatiable grasp of pale faced voracity. After having glutted our curiosity at the fountain of the Red Pipe, our horses brought us to the base of the Côteau, and then over the extended plain that lies between that and the Traverse de Sioux, on the St. Peters with about five days’ travel. In this distance we passed some of the loveliest prairie country in the world, and I made a number of sketches—“_Laque du Cygne_, Swan Lake,” (+plate+ 276), was a peculiar and lovely scene, extending for many miles, and filled with innumerable small islands covered with a profusion of rich forest trees. +Plate+ 277, exhibits the Indian mode of taking muskrats, which dwell in immense numbers in these northern prairies, and build their burrows in shoal water, of the stalks of the wild rice. They are built up something of the size and form of haycocks, having a dry chamber in the top, where the animal sleeps above water, passing in and out through a hole beneath the water’s surface. The skins of these animals are sought by the Traders, for their fur, and they constitute the staple of all these regions, being caught in immense numbers by the Indians, and vended to the Fur Traders. The mode of taking them is seen in the drawing; the women, children and dogs attend to the little encampments, while the men wade to their houses or burrows, and one strikes on the backs of them, as the other takes the inhabitants in a rapid manner with a spear, while they are escaping from them.