On the very top of this mound or ridge, we found the far-famed quarry or fountain of the Red Pipe, which is truly an anomaly in nature (+plate+ 270). The principal and most striking feature of this place, is a perpendicular wall of close-grained, compact quartz, of twenty-five and thirty feet in elevation, running nearly North and South with its face to the West, exhibiting a front of nearly two miles in length, when it disappears at both ends by running under the prairie, which becomes there a little more elevated, and probably covers it for many miles, both to the North and the South. The depression of the brow of the ridge at this place has been caused by the wash of a little stream, produced by several springs on the top, a little back from the wall; which has gradually carried away the super-incumbent earth, and having bared the wall for the distance of two miles, is now left to glide for some distance over a perfectly level surface of quartz rock; and then to leap from the top of the wall into a deep basin below, and from thence seek its course to the Missouri, forming the extreme source of a noted and powerful tributary, called the “Big Sioux.” This beautiful wall is horizontal, and stratified in several distinct layers of light grey, and rose or flesh-coloured quartz; and for most of the way, both on the front of the wall, and for acres of its horizontal surface, highly polished or glazed, as if by ignition. At the base of this wall there is a level prairie, of half a mile in width, running parallel to it; in any and all parts of which, the Indians procure the red stone for their pipes, by digging through the soil and several slaty layers of the red stone, to the depth of four or five feet.[34] From the very numerous marks of ancient and modern diggings or excavations, it would appear that this place has been for many centuries resorted to for the red stone; and from the great number of graves and remains of ancient fortifications in its vicinity, it would seem, as well as from their actual traditions, that the Indian tribes have long held this place in high superstitious estimation; and also that it has been the resort of different tribes, who have made their regular pilgrimages here to renew their pipes.