The country between the sources of Purgatory creek and the stream on which we were now encamped, is a wide and elevated formation of trap rocks, resting upon horizontal sandstone. It has a loose and scanty soil, in which sand, gravel, and rolled pebbles are rarely seen, except in the vicinity of some parts where the sandstone appears to have been uncovered by the action of currents of water. In traversing it we had collected many new and interesting plants. Among these were a large decumbent mentzelia, an unarmed rubus, with species of astragalus, pentstemon, myosotis, helianthus, &c. Beside the common purslane, one of the most frequent plants about the mountains, we had observed on the Arkansa a smaller species, remarkably pilose about the axils of the leaves, which are also narrower than in P. oleracea. A very small cuscuta also occurs almost exclusively parasitic on the common purslane.
July 31st. In attempting to descend the creek from our last encampment, we found the valley so obstructed with fragments of greenstone as to be wholly impassable. We accordingly ascended into the plain; and continuing along on the brink of the precipice, arrived in a few hours at a point where the substratum of sandstone emerges to light at the base of an inconsiderable hill. It is a fine gray sandstone, having an argillaceous cement, and its lamina are so nearly horizontal, that their inclination is not manifest to the eye. It is smooth and fissile, and in every respect remarkably contrasted to the massive and imperfectly columnar greenstone which it supports.
The greenstone of this district is not universally characterized by any tinge of green in the colouring, but often, as in the instance of which we are speaking, its colour is some shade of gray, varying from light [275] gray to grayish black. The hornblende and felspar which enter into its composition, are minutely and intimately blended. Its minute structure is rarely, if ever distinctly crystalline; most frequently it is compact, and the fracture nearly even.
The hunters were kept constantly forward of the party, and in the course of the morning they killed a small fawn and a heron. At one o'clock we arrived at the confluence of a creek tributary from the east to the stream we were following, and descending into its valley by a precipitous declivity of about four hundred feet, we encamped for the remainder of the day. This valley is bounded by perpendicular cliffs of sandstone, surmounted by extensive beds of greenstone. The fragments of the latter have fallen down into the valley, and being less perishable than the sandstone, they constitute the greater part of the débris accumulated along the base of the cliffs.
The sand-rock, which in some places is exposed in perpendicular precipices, is soft and friable, being very readily scratched with the point of a knife, and has been rudely inscribed, probably by the Indians, with emblematic figures commemorative of some past event. Several of the figures intended to represent men are distinguished by the sign of the cross inscribed near the head; some are represented smoking, and some leading horses, from which we infer, that the inscriptions are intended to commemorate some peaceful meeting of the Indians with the Spaniards of N. Mexico for the purposes of trade, when horses were either given as presents or bartered for other articles. Some meeting of this kind has probably happened here at no very distant period, as corn cobs were found near our encampment. From this circumstance it would appear, that the distance to the Spanish settlements cannot be very great.
Mr. Peale, who had been unwell since the cold storm of the 28th, now found some relief in the [276] opening of an abscess which had formed upon his jaw. As several of our horses had been lamed in descending into the valley, and by the rough journey of the preceding day, it was thought necessary to allow ourselves a day of rest. Since arriving in the country inhabited by the hitherto undescribed animal called the black-tailed or mule deer, we had been constantly attentive to the important object of procuring a complete specimen for preservation and description. Hitherto, though several had been killed, none had been brought to camp possessing all the characters of the perfect animal. Supposing we should soon pass beyond their range, a reward had been offered to the hunter who should kill and bring to camp an entire and full-grown buck.
Verplank killed one of this description, on the afternoon of the 1st of August, near enough our camp to call for assistance, and bring it in whole. They did not arrive until dark, and we had such pressing necessity for the flesh of the animal, that we could not defer dressing it until the next morning. The dimensions were accordingly taken, and a drawing made by Mr. Peale, the requisite light being furnished by a large fire. Verplank informed us, that in company with the buck which he killed, were five does, two of the common red deer, (C. virginianus) and three of the other kind.[53]
We observed about this camp, a yellow-flowering sensitive plant, apparently a congener to the saw-brier, (schrankia uncinata) of the Platte and Arkansa. Its leaves are twice pinnated, and manifestly irritable. We also added to our collection, two new species of gaura, smaller than G. mollis, which is also found here.
Several rattle-snakes were seen, and many orbicular lizards. These are evidently of two different species, differing from each other in the length of the spines and position of the nostrils. Scarce any two of either species are precisely similar in colour, but the markings are permanent. Both species possess, in a slight [277] degree, the power of varying the shades of colour. We can find no conspicuous difference, marking the different sexes in the species with long spines; the other we have not had sufficient opportunity to examine.