The traveller on the Mississippi observes with interest the innumerable islands which dot the river, and relieve the monotony of the scenery. These islands are, for the most part, covered with a luxurious growth of cotton-wood trees. They have generally been formed by what are technically called cut-offs, or new channels, from the main land. The mighty torrent, scorning its own well-beaten track, ploughs a way through the country, and returns to its channel miles below, opening at once a new path for the voyager upon its tide. The portion of land thus separated from the main shore is often subdivided by the action of the waters into several smaller islands. These islets are, however, oftener seen in isolated positions, varying in area from a few square rods to several acres. A remarkable feature of these islands is their _locomotive_ powers,--for, strange as it may seem, they annually take a step down stream! Observation has shown a change of position almost incredible. The river, continually wearing upon the up-river side of the island, washes the sands and soil to the lower side. Thus, the situation of the island is actually changed. The fact is clearly shown by the singular configuration of the mass of trees growing upon them. The wood on the upstream side of the island is of the largest size; while that on the down-stream side begins at the mere shrub, and, by a regular gradation in height, like a pair of stairs, increases to the altitude of the full-grown tree. Each successive year places a new layer of soil upon the lower side, in which the young tree takes root; and the growth of each year is distinctly visible to the traveller as he ascends the river. On one of these islands, above Vicksburg, was located a neat cottage. The island differed in many respects from others. Its area might have been eight or ten acres. On one side of it was a narrow, but deep stream, which, entering from the broad river, described a semi circle, and returned its waters on the same side. On three sides, except at the mouths of the little stream, the island was rendered inaccessible by the high banks, while on the fourth side the shrubs grew so luxuriantly as to be impervious, save to the most resolute visitor. From the high banks which walled it in the surface of the island sloped gradually towards a common centre, through which rushed the little stream. This little island had probably been a part of the main land; the river had forced its way through a valley, and, by degrees, had worn down the high land on either side, till they formed the precipices which now frowned on the visitor. The little stream had, perhaps, once been a meandering rivulet,--part of one which emptied into the river on the opposite side.