31st.--This morning we left the course of the Platte, to cross over to the Sweet Water. Our way, for a few miles, lay up the sandy bed of a dry creek, in which I found several interesting plants. Leaving this, we wended our way to the summit of the hills, of which the peaks are here eight hundred feet above the Platte, bare and rocky. A long and gradual slope led from these hills to the Sweet Water, which we reached in fifteen miles from Goat Island. I made an early encampment here, in order to give the hunters an opportunity to procure a supply from several bands of buffalo, which made their appearance in the valley near by. The stream is about sixty feet wide, and at this time twelve to eighteen inches deep, with a very moderate current.
The adjoining prairies are sandy, but the immediate river bottom is a good soil, which afforded an abundance of soft green grass to our horses, and where I found a variety of interesting plants, which made their appearance for the first time. A rain to-night made it unpleasantly cold; and there was no tree here, to enable us to pitch our single tent, the poles of which had been left at our _Cache camp_. We had, therefore, no shelter except what was to be found under cover of the _absinthe_ bushes, which grew in many thick patches, one or two and sometimes three feet high.
1st.--The hunters went ahead this morning, as buffalo appeared tolerably abundant, and I was desirous to secure a small stock of provisions; and we moved about seven mules up the valley, and encamped one mile below Rock Independence. This is an isolated granite rock, about six hundred and fifty yards long, and forty in height. Except in a depression of the summit, where a little soil supports a scanty growth of shrubs, with a solitary dwarf pine, it is entirely bare. Everywhere within six or eight feet of the ground, where the surface is sufficiently smooth, and in some places sixty or eighty feet above, the rock is inscribed with the names of travelers. Many a name famous in the history of this country, and some well known to science, are to be found mixed among those of the traders and travelers for pleasure and curiosity, and of missionaries among the savages. Some of these have been washed away by the rain, but the greater number are still very legible. The position of this rock is in longitude 107° 56', latitude 42° 29' 36". We remained at our camp of August 1st until noon of the next day, occupied in drying meat. By observation, the longitude of the place is 107° 25' 23", latitude 42° 29' 56".