The banks of the Missouri, in this part, present an alternation of low alluvial bottoms and rocky cliffs. Roche à Pierce Creek is a small stream entering nearly opposite another, called Splice Creek, a few miles above the Manito rocks. Here is a range of rocky cliffs, penetrated by numerous cavities and fissures, {81} hence called by the French boatmen, Roche a Piercè, and giving name to the creek.[114] These rocks we found filled with organic remains, chiefly encrinites. About eight or ten miles above this point the Missouri again washes the base of the rocky hills, which bound its immediate valley. The rocks advance boldly to the brink of the river, exhibiting a perpendicular front, variegated with several colours arranged in broad stripes. Here is a fine spring of water gushing out at the base of the precipice; over it are several rude paintings executed by the Indians. These cliffs are called the Big Manito rocks, and appear to have been objects of peculiar veneration with the aborigines, and have accordingly received the name of their Great Spirit. It is not to be understood that the general surface of the country, of which we are now speaking, is traversed by continuous ridges, which, in their course across the valley of the Missouri, occasion the alternation of hill and plain; which to a person ascending the river, forms the most conspicuous feature of the country. The immediate valley of the Missouri preserves great uniformity in breadth, and is bounded on both sides by chains of rocky bluffs rising from one to two hundred feet above the surface of the included valley, and separating it from those vast woodless plains which overspread so great a part of the country. Meandering from right to left along this valley the river alternately washes the base of the bluffs on either side, while, from a person passing up or down the stream, the heavy forests intercept the view of the bluffs, except at the points where they are thus disclosed. Opposite the Big Manito rocks, and the island of the same name, is the Little Saline river, on the left side; and three or four miles above, on the opposite side, a stream called the Big Manito Creek.[115] Here we passed the night of the 12th July. About midnight so violent a storm arose that we were {82} compelled to leave our encampment on shore, the tent being blown down, and to seek shelter on board the boat. Though the storm did not continue long, the water fell to the depth of one inch and an half.