Our course was a little to the east of south, nearly at right angles to the direction of the Arkansa. It was our intention to cross to and ascend the First Fork, a considerable stream, entering the Arkansa eighteen miles below our last encampment. After leaving the river we found the surface to rise gradually till, at the distance of six or eight miles, it is broken by a few small gravelly ridges. These are of little elevation; and their summits overlook an extensive waste of sand, terminated towards the south and east only by the verge of the sky, on the west and north-west by the snowy summits of the Spanish mountains. As our way led across the general course of the stream, we met with no water, except such as was still standing in puddles, which had been filled by the last night's rain. Near one of these we halted to dine. The thermometer, hanging in the shade of our tent, the most perfect, and indeed the only shade we could find, stood at 100°. The little water we could procure was thick with mud, and swarming with the larva of mosquitos; but this we regretted the less, as we had no cooking to perform. We dined upon jerked meat from our packs. Some animals, seen at a distance, {256} were at first mistaken for bisons; but were found, by the hunters sent in pursuit of them, to be horses, and too wild and vigilant to be taken. A species of cone-flower (rudbeckia tagetes)[42] with an elongated receptacle, and large red brown radial florets, was observed about the margin of the stagnant pool near which we halted. We also collected the linum rigidum, and a semi-procumbent species of sida, which appears to be undescribed. It is a little larger than the S. spinosa, to which it has some general resemblance. The whole tract passed in this day's journey of twenty-seven miles, is sterile and sandy. At sunset we were so fortunate as to meet with another small pool of water, by which we pitched our tent, and kindled a fire with the dung of the bison. Since leaving the Arkansa, we had scarcely seen so much wood as, if collected, would have supplied us for a single night. We passed, in the course of the day, not less than four or five paths, leading south-west, towards the Spanish settlements. Some of them appeared to have been recently travelled by men with horses, such paths being easily distinguished from those of bisons or wild horses.[43]