isinglass, pyrites, and sandstone, the two first very pure. Above this
bluff comes in a small creek on the south, which we call Rologe creek.
Seven miles above is another cliff, on the same side, of allum rock, of
a dark brown colour, containing in its crevices great quantities of
cobalt, cemented shells, and red earth. From this the river bends to the
eastward, and approaches the Sioux river within 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