The red sandstone, apparently the most extensive of the rocky formations of this region, has, wherever it occurs, indications of the presence of muriate of soda, and almost as commonly discloses veins and beds of sulphate of lime. The substance last mentioned had been growing more and more abundant since we left the region of the trap rocks at the sources of the river. It was now so frequent as to be conspicuous in all the exposed portions of the sand-rock, and was often seen from a distance of several miles. It occurs under various forms, sometimes we meet with the most beautiful selenite, disposed in broad reticulating veins, traversing the sandstone; the granular and fibrous varieties, whose snowy whiteness contrasts strongly with the deep red and brown of the sandstone, are sometimes seen in thin horizontal lamina, or scattered about the surface, sometimes included in larger masses of the common amorphous plaister-stone. This last is usually of a colour approaching to white, but the exposed surfaces are more or less tinged with the colouring matter of the sand-rock, and all the varieties are so soft as to disintegrate rapidly when exposed to the air. Recent surfaces show no ferruginous tinge; { 320} or rather, we would say, this colour does not appear to have been contemporaneous to the formation of the sulphate of lime, but derived from the cement of the sandstone, and to have penetrated no farther than it has been carried by the impetration of water.
We left our encampment at 5 o'clock, the morning fair; thermometer at 62°. Our courses regulated entirely by the direction of the river, were north fifty-five east, eleven miles; then north, ten east, seven miles; in all eighteen miles before dinner.[65] The average direction of our courses for some days had been rather to the north, than south of east. This did not coincide entirely with our previous ideas of the direction of Red river, and much less of the Faux Ouachitta, or False Washita,[66] which being the largest of the upper branches of the Red river from the north, we believed, might be the stream we were descending. From observations taken at several points along the river we had ascertained, that we must travel three or four days' journey to the south, in order to arrive at the parallel of the confluence of the Kiamesha with the Red river,[67] and we were constantly expecting a change in the direction of our courses. The confident assurance of the Kaskaias, that we were on the Red river, and but a few days march above the village of the Pawnee Piquas, tended to quiet the suspicions we began to feel on this subject. We had now travelled, since meeting the Indians, a greater distance than we could suppose they had intended to indicate by the admeasurement of ten "lodge days," but we were conscious our communications with them had been made through inadequate interpreters, and it was not without reason, we began to fear we might have received erroneous impressions. In the afternoon, however, the river inclined more { 321} to the direction we wished to travel, and we had several courses to the south of east. At sunset we pitched our tent on the north side of the river, and dug a well in the sand, which afforded a sufficient supply of wholesome, though brackish, water. Throughout the night the roaring of immense herds of bisons, and the solemn notes of the hooting owl were heard, intermixed with the desolate cries of the jackal and the screech-owl. The mulberry, and the guilandina, growing near our camp, with many of the plants and birds we had been accustomed to see in the frontier settlements of the United States, reminded us of the comforts of home and the cheering scenes of civilized society, giving us at the same time the assurance that we were about to arrive at the point where we should take leave of the desert.