At noon we halted near the base of a hill of this description. It is of green stone, and the sandrock on which it rests is disclosed at the bottom of a ravine which commences near the foot of the hill. This latter rock is of a slaty structure, and embraces narrow beds of bituminous clay slate, which contains pieces of charcoal, or the carbonised remains of vegetables, in every possible respect resembling the charcoal {268} produced by the process of combustion in the open air. In the ravines and over the surface of the soil we observed masses of a light porous reddish-brown substance, greatly resembling that which is so often seen floating down the Missouri, and has by some been considered a product of pseudo-volcanic fires, said to exist on the upper branches of that river.[50] We also saw some porphyritic masses with a basis of greenstone, containing crystals of felspar. In the afternoon several magpies, shore larks, and cow buntings were seen. One of the cow buntings followed us five or six miles, alighting on the ground, near the foremost of our line, and within a few paces of our horses' feet, where he stood gazing at the horses until all had passed him, when he again flew forward to the front, repeating the same movement many times in succession. We had now arrived near that part of the country, where, according to the information of the Kaskaia, we expected to find the remarkable saline spring from which we were told the Indians often procured large masses of salt. The Kaskaia had, by the aid of a map traced in the sand, given us a minute account of the situation of the spring and of the surrounding country, stating that the salt existed in masses at the bottom of a basin-like cavity, which contained about four and a half feet of reddish water. Thus far we had not found a single feature of the country to correspond in the slightest degree to his descriptions, and as we had been careful to follow the general direction of the course he pointed out to us, it was probably his intention to deceive.