The narrative of the expedition was written by the commanders from day to day, and published after their return. We shall tell the story of their adventures nearly in the language of their own journal, with such abridgments as our plan renders necessary. May 14, 1804.--All the preparations being completed, they left their encampment this day. The character of the river itself was the most interesting object of examination for the first part of their voyage. Having advanced, in two months, about four hundred and fifty miles, they write as follows: "The ranges of hills on opposite sides of the river are twelve or fifteen miles apart, rich plains and prairies, with the river, occupying the intermediate space, partially covered near the river with cotton-wood or Balm-of-Gilead poplar. The whole lowland between the parallel ranges of hills seems to have been formed of mud of the river, mixed with sand and clay. The sand of the neighboring banks, added to that brought down by the stream, forms sand-bars, projecting into the river. These drive the stream to the opposite bank, the loose texture of which it undermines, and at length deserts its ancient bed for a new passage. It is thus that the banks of the Missouri are constantly falling in, and the river changing its bed. "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." RIVER SCENERY. "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.