Thursday, August 25.--Last night was very cold, the thermometer marking 40 degrees at 8 o'clock a.m. At one mile of travel we came to the middle cañon, which we passed on a very narrow trail running over a high spur of the mountain overlooking the river, which at this point is forced through a narrow gorge, surging and boiling and tumbling over the rocks, the water having a dark green color. After passing the cañon we again left the valley, passing over the mountain, on the top of which at an elevation of several hundred feet above the river is a beautiful lake. Descending the mountain again, we entered the valley, which here is about one and a half to two miles wide. At nineteen miles from our morning camp we came to Gardiner's river, at the mouth of which we camped. We are near the southern boundary of Montana, and still in the limestone and granite formations. Mr. Everts came into camp just at night, nearly recovered, but very tired from his long and tedious ride over a rugged road, making our two days' travel in one. We passed to-day a singular formation which we named "The Devil's Slide," From the top of the mountain to the valley, a distance of about 800 feet, the trap rock projected from 75 to 125 feet, the intermediate layers of friable rock having been washed out. The trap formation is about twenty-five feet wide, and covered with stunted pine trees. Opposite our camp is a high drift formation of granite boulders, gravel and clay. The boulders are the regular gray Quincy granite, and those in the middle of the river are hollowed out by the action of the water into many curious shapes. We have here found our first specimens of petrifactions and obsidian, or volcanic glass. From the top of the mountain back of our camp we can see to-night a smoke rising from another peak, which some of our party think is a signal from one band of the Indians to another, conveying intelligence of our progress. Along our trail of to-day are plenty of Indian "signs," and marks of the lodge poles dragging in the sand on either side of the trail.[E] Jake Smith stood guard last night, or ought to have done so, and but for the fact that Gillette was also on guard, I should not have had an undisturbed sleep. We know that the Indians are near us, and sleep is more refreshing to me when I feel assured that I will not be joined in my slumbers by those who are assigned for watchful guard duty. [Illustration: S.T. Hauser]