Sept. 24. American Falls. The river here enters between low mural banks, which consists of a fine vesicular trap rock, the intermediate portions being compact and crystalline. Gradually becoming higher in its downward course, these banks of scoriated volcanic rock form, with occasional interruptions, its characteristic features along the whole line to the Dalles of the Lower Columbia, resembling a chasm which had been rent through the country, and which the river had afterwards taken for its bed. In the south is a bordering range of mountains, which, although not very high, are broken and covered with snow; and at a great distance to the north is seen the high, snowy line of the Salmon river mountains, in front of which stand out prominently in the plain the three isolated rugged-looking little mountains commonly known as the Three Buttes. Between the river and the distant Salmon river range, the plain is represented by Mr. Fitzpatrick as so entirely broken up and rent into chasms as to be impracticable for a man even on foot. In the sketch annex, the point of the view is low, but it conveys very well some idea of the open character of the country, with the buttes rising out above the general line. By measurement, the river above is 870 feet wide, immediately contracted at the fall in the form of a lock by jutting piles of scortaceous basalt, over which the foaming river must present a grand appearance at the time of high water.
- Frémont's report

Sept. 30. Subterranean River. Immediately opposite to us, a subterranean river bursts out directly from the face of the escarpment, and falls in white foam to the river below. In the views annexed you will find, with a sketch of this remarkable fall, a representation of the mural precipices which enclose the main river, and which form its characteristic feature along a great portion of its course. A melancholy and strange-looking country - one of fracture, and violence, and fire.
- Frémont's report

October 6. Change in the face of the country - The morning warm, the thermometer 46° at sunrise, the sky entirely clouded. After travelling about three miles over and extremely rocky road, the volcanic fragments began to disappear; and, entering among the hills at the point of the mountain, we found ourselves suddenly in granite country. Here the character of the vegetation was very much changed; the artemisia disappeared almost entirely, showing only at intervals towards the close of the day, and was replaced by Purshia tridentata, with flowering shrubs and small fields of dieteria divaricata, which gave bloom and gayety to the hills. These were every where covered with a fresh and green short grass, like that of the early spring. This is the fall or second growth, the dried grass having been burnt off by the the [sic] Indians; and wherever the fire has passed, the bright-green color is universal. The soil among the hills is altogether different from that of the river plain, being in many places black, in others sandy and gravelly, but of a firm and good character; appearing to result from the decomposition of the granite rocks, which is proceeding rapidly.
- Frémont's report

October 8. Fort Boisée. This is a simple dwelling-house on the right bank of Snake River, about a mile below the mouth of Rivière Boisée; and on our arrival we were received with an agreeable hospitality by Mr. Payette, an officer of the Hudson Bay Company, in charge of the fort; all of whose garrison consisted in a Canadian engagé.
- Frémont's report

October 1. Fishing Falls. Our encampment was about one mile below the Fishing Falls, a series of cataracts with very inclined planes, which are probably so named because they form a barrier to the ascent of the salmon; and the great fisheries from which the inhabitants of this barren region almost entirely derive a subsistence commence at this place. These appeared to be unusually gay savages, fond of laughter; and, in their apparent good nature and merry character, struck me as being entirely different from the Indians we had been accustomed to see. From several who visited our camp in the evening, we purchased, in exchange for goods, dried salmon. At this season they are not very fat, but we were easily pleased. The Indians made us comprehend, that when the salmon came up the river in the spring, they are so abundant that they merely throw in their spears at random, certain of bringing out a fish.
- Frémont's report

October 5. Hot Springs. The morning was calm and clear, and at sunrise the thermometer was at 32°. The road to day was occasionally extremely rocky, with hard volcanic fragments, and our travelling very slow. In about nine miles the road brought us to a group of smoking hot springs, with a temperature of 164°. There were a few helianthi in bloom, with some other low plants, and the place was green round about, the ground warm, and the air pleasant, with a summer atmosphere that was very grateful in a day of high and cold searching wind. The roads were covered in a white and red incrustation; and the water has on the tongue the same unpleasant effect as that of the Basin spring on Bear River. They form several branches and bubble up with force enough to raise small pebbles several inches.
- Frémont's report