The country, for several miles to the west of the range of hills mentioned above, is as uniformly plain as that on any part of the Platte. It differs from that further to the east only in being of a coarser sand, and in an aspect of more unvaried sterility. The cactus ferox reigns sole monarch, and sole possessor {173} of thousands of acres of this dreary plain. It forms patches which neither a horse nor any other animal will attempt to pass over. The rabbit's foot plantation, and a few brown and withered grasses, are sparingly scattered over the intervening spaces. In depressed and moist situations, where the soil is not so entirely unproductive, the variegated spurge (euphorbia variegata), with its painted involucrum and party-coloured leaves, is a conspicuous and beautiful ornament. The lepidium virginicum, distributed over every part of northern and equinoctial America, from Hudson's Bay to the summit of the Silla of Caraccas,[122] is here of such diminutive size that we were induced to search, though we sought in vain, for some character to distinguish it as a separate species. [122] See Humb. Pers. Nar. vol. iii. p. 500.—JAMES. At three o'clock P. M. the planet Venus was distinctly visible. Its distance from the sun at 3h. 45m. was east 36° 15[']. There were a few broken cumulostratose clouds from the south-west, otherwise the sky was clear, and near the zenith, where the star was seen, of a deep and beautiful azure. Our actual elevation, at this time, must have been considerable, and might be supposed to effect, in some degree, the transparency of our atmosphere. Several magpies were seen about the islands in the river, where it is probable they rear their young. On the 30th we left the encampment at our accustomed early hour, and at eight o'clock were cheered by a distant view of the Rocky Mountains. For some time we were unable to decide whether what we saw were mountains, or banks of cumulous clouds skirting the horizon, and glittering in the reflected rays of the sun. It was only by watching the bright parts, and observing that their form and position remained unaltered, that we were able to satisfy ourselves they were indeed mountains. They were visible from the lowest parts of the plain, and {174} their summits were, when first discovered, several degrees above our horizon. They became visible by detaching themselves from the sky beyond, and not by emerging from beneath the sensible horizon, so that we might have seen them from a greater distance had it not been for the want of transparency in the atmosphere. Our first views of the mountains were indistinct, on account of some smokiness of the atmosphere, but from our encampment, at noon, we had a very distinct and satisfactory prospect of them. A small part only of the intervening plain was visible, the convexity of the surface intercepting the view from the base of the mountains, and that portion of the plain adjacent to it.