Those boundless prairies, whose monotony is unbroken by a single hillock, were succeeded by a sandy desert gradually sloping up, for a distance of nearly four hundred miles, to the Rocky Mountains. This desert, broken by precipitous ravines, _canons_, and gorges, at the bottom of which gurgles some insignificant stream, its banks clothed with stunted and meagre vegetation, produces nothing but cacti with sharp and formidable prickles. On the 6th July, the expedition reached the foot of the Rocky Mountains. Dr. James scaled one of the peaks, to which he gave his own name, and which rises to a height of 11,500 feet above the sea level. "From the summit of the peak," says the botanist, "the view towards the north, west, and south-west, is diversified with innumerable mountains all white with snow, and on some of the more distant it appears to extend down to their bases. Immediately under our feet on the west, lay the narrow valley of the Arkansas; which we could trace running towards the north-west, probably more than sixty miles. On the north side of the peak was an immense mass of snow and ice.... To the east lay the great plain, rising as it receded, until, in the distant horizon, it appeared to mingle with the sky." Here the expedition was divided into two parties, one, under the command of Major Long, to make its way to the sources of the Red River, the other, under Captain Bell, to go down the Arkansas as far as Port Smith. The two detachments separated on the 24th July. The former, misled by the statements of the Kaskaia Indians and the inaccuracy of the maps, took the Canadian for the Red River, and did not discover their mistake until they reached its junction with the Arkansas. The Kaskaias were the most miserable of savages, but intrepid horsemen, excelling in lassoing the wild mustangs which are descendants of the horses imported into Mexico by the Spanish conquerors. The second detachment was deserted by four soldiers, who carried off the journals of Say and Lieutenant Swift with a number of other valuable effects. Both parties also suffered from want of provisions in the sandy deserts, whose streams yield nothing but brackish and muddy water. The expedition brought to Washington sixty skins of wild animals, several thousands of insects, including five hundred new species, four or five hundred specimens of hitherto unknown plants, numerous views of the scenery, and the materials for a map of the districts traversed. [Illustration: "Excelling in lassoing the wild mustangs."]