If the river of which we speak should at any season of the year contain water enough for the purposes of navigation, it is probable the fall occasioned by the rocky traverse above mentioned will be sufficient to prevent the passage upwards. The point is a remarkable one, as being the locality of a rare and beautiful variety of sandstone. The rock which appears in the bed of the river is a compact slaty {24} sandstone, of a deep green colour, resembling some varieties of chloritic slate. Whether the colour depends upon epidote, chlorite, or some other substance, we were not able to determine. The sandstone is micaceous, but the particles of mica, as well as those of the other integrant minerals, are very minutely divided. The same rock, as we found by tracing it to some distance, becomes of a light grey colour, and contains extensive beds of bituminous clay-slate. Its stratifications are so little inclined, that their dip cannot be estimated by the eye. This point, though scarce deserving the name of a cataract, is so marked by the occurrence of a peculiar bed of rocks crossing the river, and by the rapid descent of the current, that it may be readily recognized by any who shall pass that way hereafter. In this view we attach some importance to it, as the only spot in a distance of six hundred miles we can hope to identify by description. In ascending, when the traveller arrives at this point, he has little to expect beyond, but sandy wastes and thirsty inhospitable steppes. The skirts of the hilly and wooded region extend to a distance of fifty or sixty miles above, but even this district is indifferently supplied with water. Beyond commences the wide sandy desert, stretching westward to the base of the Rocky Mountains. We have little apprehension of giving too unfavourable an account of this portion of the country. Though the soil is in some places fertile, the want of timber, of navigable streams, and of water for the necessities of life, render it an unfit residence for any but a nomade population. The traveller who shall at any time have traversed its desolate sands, will, we think, join us in the wish that this region may for ever remain the unmolested haunt of the native hunter, the bison, and the jackall.[81]