To the south, along our line of march to-day, the main chain of the Black
or Laramie hills rises precipitously. Time did not permit me to visit
them; but, from comparative information, the ridge is composed of the
coarse sandstone or conglomerate hereafter described. It appears to enter
the region of clouds, which are arrested in their course, and lie in
masses along the summits. An inverted cone of black cloud (cumulus) rested
during all the forenoon on the lofty peak of Laramie mountain, which I
estimated to be about two thousand feet above the fort, or six thousand
five hundred above the sea. We halted to noon on the _Fourche Amere_,
so called from being timbered principally with the _liard amere_, (a
species of poplar,) with which the valley of the little stream is
tolerably well wooded, and which, with large expansive summits, grows to
the height of sixty or seventy feet.

The bed of the creek is sand and gravel, the water dispersed over the
broad bed in several shallow streams. We found here, on the right bank, in
the shade of the trees, a fine spring of very cold water. It will be
remarked that I do not mention, in this portion of the journey, the
temperature of the air, sand, springs, &c.--an omission which will be
explained in the course of the narrative. In my search for plants, I was
well rewarded at this place.

With the change in the geological formation on leaving Fort Laramie, the
whole face of the country has entirely altered its appearance. Eastward of
that meridian, the principal objects which strike the eye of a traveler
are the absence of timber, and the immense expanse of prairie, covered
with the verdure of rich grasses, and highly adapted for pasturage.
Wherever they are not disturbed by the vicinity of man, large herds of
buffalo give animation to this country. Westward of Laramie river, the
region is sandy, and apparently sterile; and the place of the grass is