"he has no horse, and expects you to give him one." I described to him the
place where I intended to encamp, and, shaking hands, in a few minutes we
were among the hills, and this last habitation of whites shut out from our
view.

The road led over an interesting plateau between the North fork of the
Platte on the right, and Laramie river on the left. At the distance of ten
miles from the fort, we entered the sandy bed of a creek, a kind of
defile, shaded by precipitous rocks, down which we wound our way for
several hundred yards, to a place where, on the left bank, a very large
spring gushes with considerable noise and force out of the limestone rock.
It is called the "Warm Spring," and furnishes to the hitherto dry bed of
the creek a considerable rivulet. On the opposite side, a little below the
spring, is a lofty limestone escarpment, partially shaded by a grove of
large trees, whose green foliage, in contrast with the whiteness of the
rock, renders this a picturesque locality. The rock is fossiliferous, and,
so far as I was able to determine the character of the fossils, belongs to
the carboniferous limestone of the Missouri river, and is probably the
western limit of that formation. Beyond this point I met with no fossils
of any description.

I was desirous to visit the Platte near the point where it leaves the
Black hills, and therefore followed this stream, for two or three miles,
to its mouth, where I encamped on a spot which afforded good grass and
_prele (equisetum)_ for our animals. Our tents having been found too
thin to protect ourselves and the instruments from the rains, which in
this elevated country are attended with cold and unpleasant weather, I had
procured from the Indians at Laramie a tolerably large lodge, about
eighteen feet in diameter, and twenty feet in height. Such a lodge, when
properly pitched, is, from its conical form, almost perfectly secure