In the middle of the day we found the heat more oppressive, with the mercury at 96°, than we had known it in many instances when the thermometer had indicated a higher temperature by six or eight degrees. This sultry calm, was, however, soon succeeded by thunder-showers, attended with their ordinary effects upon the atmosphere. In the afternoon the country we passed was swarming with innumerable herds of bison, wild horses, deer, elk, &c. while great numbers of minute sand-pipers, yellow-shanked snipes, killdeer plovers, (charadrius vociferus,) and telltale godwits about the river, seemed to indicate the vicinity of larger bodies of water than we had been accustomed of late to see. During the afternoon and the night there was a continual and rapid alternation of bright calm and cloudless skies, with sudden and violent thunder-storms. Our horizon was a little obscured on both sides by the hills and the scattered trees which skirted along the sides of the valley. As we looked out of our tent to observe the progress of the night, we found sometimes a pitchy darkness veiling every object; at others, by the clear light of the stars and the constant flashing from some unseen cloud, we could distinguish all the features of the surrounding scene: our horses grazing quietly about our tent, and the famished jackal prowling near, to seize the fragments of our plentiful supper. The thunder was almost incessant, but its low and distant mutterings were at times so blended with the roaring of the bisons, that more experienced ears than ours might have found a difficulty in distinguishing between them. At a late hour in the night some disturbance was perceived among the horses, occasioned by a herd of wild horses, who had {328} come in, and struck up a hasty acquaintance with their enslaved fellow brutes.