After having spent nearly five months in this dreary abode, the ice broke up, the boats were repaired and once more got into the river; and other preparations were made for the voyagers to pursue their course towards the sources of the Missouri. In the afternoon of Sunday, the 7th of April, the arrangements being all completed, the party, consisting of thirty-two persons, once more embarked. They now occupied six small canoes and two large pirogues. The barge was sent down the river, to the United States, with presents of natural curiosities, which had been collected, and with dispatches to the president. At some distance from Fort Mandan, the land, on each side of the Missouri, after ascending the hills near the water, exhibits the appearance of one fertile and unbroken plain, which extends as far as the eye can reach, without a solitary tree or shrub, except in moist situations, or in the steep declivities of hills. In some parts the plains were on fire; for, every spring, as soon as the ice breaks up in the river, these plains are set on fire by the Indians, for the purpose of driving out and attacking the buffaloes, and other wild animals which inhabit them. Beavers were here very abundant. A herd of antelopes, and the track of a large white bear, were seen in the plain: geese and swans were observed, in great numbers. The musquitoes now began to be very troublesome. Before the middle of April, the weather became so warm, that, in the day-time, the men worked with no clothes on, except round their waist. On the twelfth, the voyagers reached the mouth of the _Little Missouri_, where they remained during the day, for the purpose of making celestial observations. This river falls into the Missouri, on its south side, and at the distance of sixteen hundred and ninety-three miles above its confluence with the Mississippi. Its current is strong, and its width a hundred and thirty-four yards; but its greatest depth is only two feet and half. The adjacent country is hilly and irregular; and the soil is, for the most part, a rich dark-coloured loam, intermixed with a small proportion of sand. On the thirteenth, the voyagers passed the remains of forty-three temporary lodges, which were supposed to have belonged to the Assiniboin Indians. The waters of many of the creeks were found to be so strongly impregnated with mineral salts, that they were not fit to be drunk. On each bank of the Missouri the country presented the appearance of low plains and meadows; bounded, at the distance of a few miles, by broken hills, which end in high, level, and fertile lands: the quantity of timber was increasing. In the timbered-grounds, higher up the river, the voyagers observed a great quantity of old hornets' nests. Many of the hills exhibited a volcanic appearance, furnishing great quantities of lava and pumice stone: of the latter, several pieces were observed floating down the river. In all the copses there were remains of Assiniboin encampments.