The Kaskaia Indians had told us, that before we arrived at the village of the Pawnee Piquas, we should pass a range of blue hills. These we concluded could be no other than hills whose sides were covered with forests, like those we were now passing, and accordingly we watched with some anxiety for the appearance of something which should indicate the vicinity of an Indian village. As we pursued our way along the serpentine bed of the river, the valley became narrower, the hills more elevated, and as we crossed the rocky points of their bases, we could not {16} but observe that the sandstone was of a different character from any we had before seen. It contains more mica than that of the Alleghanies, or that of the secondary hills along the base of the Rocky Mountains; it glitters conspicuously, like mica-slate when seen in the sunshine; and this, as we found by examination, does not depend entirely on the great proportion of mica it contains, but also in some degree upon the crystalline surfaces of the minute particles. Its cement is often argillaceous, and this, as well as the impressions of some organic relics[77] we observed in it, induced us to expect the occurrence of coal-beds. On ascending the hills from the place of our midday encampment, we found this sandstone at an elevation of about two hundred feet (according to our estimate) from the bed of the river, succeeded by a stratum of limestone of the common compact blue variety, abounding in casts of anomias, entrochi, &c. This rests horizontally upon the summits of the hills, and disintegrating less rapidly than the sandstone which forms their bases, it is sometimes left projecting in such a manner as to render access impossible. Climbing to the summit of some of the hills near the river, we had the view towards the south and east of a wild and mountainous region, covered with forests, where, among the brighter verdure of the oak, the nyssa, and the castanea pumila, we distinguished the darker shade of the juniper, and others of the coniferæ. A little before arriving at the place of our evening encampment, we observed the track of a man who had passed on foot, and with bare feet, down the river. This we were confident could be no other than the track of our lost interpreter Adams. What accident could have deprived him of his mule we {17} were at a loss to conjecture. We found it equally difficult to account for his pushing forward with such perseverance, when he must have had every reason to believe we were behind him.