"On one occasion, the party encamped on a sand-bar in the river. Shortly after midnight, the sleepers were startled by the sergeant on guard crying out that the sand-bar was sinking: and the alarm was timely given; for scarcely had they got off with the boats before the bank under which they had been lying fell in; and, by the time the opposite shore was reached, the ground on which they had been encamped sunk also.
"We had occasion here to observe the process of the undermining of these hills by the Missouri. The first attacks seem to be made on the hills which overhang the river. As soon as the violence of the current destroys the grass at the foot of them, the whole texture appears loosened, and the ground dissolves, and mixes with the water. At one point, a part of the cliff, nearly three-quarters of a mile in length, and about two hundred feet in height, had fallen into the river. As the banks are washed away, the trees fall in, and the channel becomes filled with buried logs."
"July 12.—We remained to-day for the purpose of making lunar observations. Capt. Clarke sailed a few miles up the Namaha River, and landed on a spot where he found numerous artificial mounds.
NOTE. A late traveller, Rev. Samuel Parker, speaks thus of these mounds: "The mounds, which some have called the work of unknown generations of men, were scattered here in all varieties of form and magnitude, thousands in number. Some of them were conical, some elliptical, some square, and some parallelograms. One group attracted my attention particularly. They were twelve in number, of conical form, with their bases joined, and twenty or thirty feet high. They formed two-thirds of a circle, with an area of two hundred feet in diameter. If these were isolated, who would not say they were artificial? But, when they are only a group among a thousand others, who will presume to say they all are the work of man?...
"It is said by those who advocate the belief that they are the work of ancient nations; that they present plain evidence of this in the fact that they contain human bones, articles of pottery, and the like. That some of them have been used for burying-places, is undoubtedly true; but may it not be questioned whether they were made, or only selected, for burying-places? No one who has ever seen the thousands and ten thousands scattered through the Valley of the Mississippi will be so credulous as to believe that a hundredth part of them were the work of man."
"From the top of the highest mound, a delightful prospect presented itself,—the lowland of the Missouri covered with an undulating grass nearly five feet high, gradually rising into a second plain, where rich weeds and flowers were interspersed with copses of the Osage plum. Farther back from the river were seen small groves of trees, an abundance of grapes, the wild cherry of the Missouri,—resembling our own, but larger, and growing on a small bush. The plums are of three kinds,—two of a yellow color, and distinguished by one of the species being larger than the other; a third species of red color. All have an excellent flavor, particularly the yellow kind."
PIPE-CLAY ROCK.
"Aug. 21.—We passed the mouth of the Great Sioux River. Our Indian interpreter tells us that on the head waters of this river is the quarry of red rock of which the Indians make their pipes; and the necessity of procuring that article has introduced a law of nations, by which the banks of the stream are sacred; and even tribes at war meet without hostility at these quarries, which possess a right of asylum. Thus we find, even among savages, certain principles deemed sacred, by which the rigors of their merciless system of warfare are mitigated."