We had continued our march until near sunset, expecting constantly to come in view of the river, which we were persuaded must soon make a great bend to the south, but perceiving the night would overtake us in the plains, we began to search for a place to encamp. The bison paths in this country are as frequent and almost as conspicuous as the roads in the most populous parts of the United States. These converge from all directions to the places where water is to be found, and by following their guidance we were soon led to a spot where was found a small spring dripping from the side of a cliff of sandstone. The water collected in a little basin at the foot of the cliff, and flowing a few rods down a narrow ravine, disappeared in the sand. Having established our camp, we travelled down this ravine, searching for plants, while any daylight remained. The rocks were beautifully exposed, but exhibited no appearance unlike what we had been accustomed to see along the river--the red indistinctly stratified sand-rock, spotted and veined with plaster-stone and selenite. About the shelvings and crevices of the rocks, the slender corolla of the œnothera macrocarpa, and the purple blossoms of the pentstemon bradburis, lay withering together, while the fading leaves and the ripening fruit seemed to proclaim the summer near its end. On the morning following we resumed our march, altering our course from S. E. to N. E. The want of water in the hills compelled us again to seek the river. Falling in with a large bison path, which we {325} knew would conduct us by the easiest and most direct route, we travelled about fifteen miles, and encamped at noon on the bank of the river. In returning to the low grounds, we passed some grassy pastures, carpeted with the densest and finest verdure, and sprinkled with herds of deer, antelopes, and bisons. In some places the ground was covered with a purple mat of the aculeate leaves and branches of a procumbent eryngo; here rose the tall and graceful head of the centaurea speciosa,[69] there, in more retiring beauty, crept a humble dalea, or an ascending petalostemum. As we approached the river, we discovered a fine herd of bisons, in the grove where we intended to place our camp, some lying down in the shade, others standing in the pool of water, which extended along under the bank. Dismounting from our horses, and approaching under cover of the bushes, we shot two of the fattest, but before we had time to reload our pieces, after the second fire, we perceived a bull running towards us, evidently with the design to make battle; we, however, gave him the slip, by escaping into the thick bushes, and he turned off to follow the retiring herd.