The explorers judged that the cold was somewhat unusual for that locality, inasmuch as the cottonwood trees lost their leaves by the frost, showing that vegetation, generally well suited to the temperature of its country, or habitat, had been caught by an unusual nip of the frost. The explorers noticed that the air of those highlands was so pure and clear that objects appeared to be much nearer than they really were. A man who was sent out to explore the country attempted to reach a ridge (now known as the Little Rocky Mountains), apparently about fifteen miles from the river. He travelled about ten miles, but finding himself not halfway to the object of his search, he returned without reaching it. The party was now just westward of the site of the present town of Carroll, Montana, on the Missouri. Their journal says:-- “The low grounds are narrow and without timber; the country is high and broken; a large portion of black rock and brown sandy rock appears in the face of the hills, the tops of which are covered with scattered pine, spruce, and dwarf cedar; the soil is generally poor, sandy near the tops of the hills, and nowhere producing much grass, the low grounds being covered with little else than the hyssop, or southernwood, and the pulpy-leaved thorn. Game is more scarce, particularly beaver, of which we have seen but few for several days, and the abundance or scarcity of which seems to depend on the greater or less quantity of timber. At twenty-four and one-half miles we reached a point of woodland on the south, where we observed that the trees had no leaves, and camped for the night.” The “hyssop, or southernwood,” the reader now knows to be the wild sage, or sage-brush. The “pulpy-leaved thorn” mentioned in the journal is the greasewood; and both of these shrubs flourish in the poverty-stricken, sandy, alkaline soil of the far West and Northwest. The woody fibre of these furnished the only fuel available for early overland emigrants to the Pacific. The character of this country now changed considerably as the explorers turned to the northward, in their crooked course, with the river. On the twenty-fifth of May the journal records this:-- “The country on each side is high, broken, and rocky; the rock being either a soft brown sandstone, covered with a thin stratum of limestone, or else a hard, black, rugged granite, both usually in horizontal strata, and the sand-rock overlaying the other. Salts and quartz, as well as some coal and pumice-stone, still appear. The bars of the river are composed principally of gravel; the river low grounds are narrow, and afford scarcely any timber; nor is there much pine on the hills. The buffalo have now become scarce; we saw a polecat (skunk) this evening, which was the first for several days; in the course of the day we also saw several herds of the bighorned animals among the steep cliffs on the north, and killed several of them.”