thin three or four miles. We
sailed the greater part of the day, and made nineteen miles to our camp
on the north side. The sandbars are as usual numerous: there are also
considerable traces of elk; but none are yet seen. Captain Lewis in
proving the quality of some of the substances in the first cliff, was
considerably injured by the fumes and taste of the cobalt, and took some
strong medicine to relieve him from its effects. The appearance of these
mineral substances enable us to account for disorders of the stomach,
with which the party had been affected since they left the river Sioux.
We had been in the habit of dipping up the water of the river
inadvertently and making use of it, till, on examination, the sickness
was thought to proceed from a scum covering the surface of the water
along the southern shore, and which, as we now discovered, proceeded
from these bluffs. The men had been ordered, before we reached the
bluffs, to agitate the water, so as to disperse the scum, and take the
water, not at the surface, but at some depth. The consequence was, that
these disorders ceased: the biles too which had afflicted the men, were
not observed beyond the Sioux river. In order to supply the place of
sergeant Floyd, we permitted the men to name three persons, and Patrick
Gass having the greatest number of votes was made a sergeant.

August 23. We set out early, and at four miles came to a small run
between cliffs of yellow and blue earth: the wind, however, soon
changed, and blew so hard from the west, that we proceeded very slowly;
the fine sand from the bar being driven in such clouds, that we could
scarcely see. Three and a quarter miles beyond this run, we came to a
willow island, and a sand island opposite, and encamped on the south
side, at ten and a quarter miles. On the north side is an extensive and
delightful prairie, which we called Buffaloe prairie, from our having
here killed the first buffaloe. Two elk swam the river to-day and were
fired at, but escaped: a deer was killed from the boat; one beaver was
killed; and several prairie wolves were seen.

August 24. It began to rain last night, and continued this morning: we
proceeded, however, two and a quarter miles, to the commencement of a
bluff of blue clay, about one hundred and eighty, or one hundred and
ninety feet on the south side: it seems to have been lately on fire; and
even now the ground is so warm that we cannot keep our hands in it at
any depth: