_ and _Missouri Indians_ with whom the voyagers had an
interview after this, were almost naked, having no covering, except a
cloth round their middle, and a loose blanket or buffalo robe thrown
over their shoulders.

In one place Captain Lewis noticed that the hills which extended to the
edge of the river on the south side, contained alum, copperas, cobalt,
(having the appearance of soft isinglass,) pyrites, and sand-stone: the
two first very pure. In another cliff, seven miles distant, he observed
an alum rock, of dark brown colour, containing, in its crevices, great
quantities of cobalt, cemented shells, and red earth. The appearance of
these mineral substances enabled him to account for some disorders of
the stomach with which his men had of late been much afflicted. They had
been in the habit of dipping up the water of the river inadvertently,
and drinking it; and he had now no doubt but the sickness was occasioned
by a scum which covered its surface along the southern shore. Always
after this the men agitated the water, so as to disperse the scum,
before they drank of it, and these disorders ceased.

The soil of a plain over which the two commanders and some of the men
walked, on the 25th, was exceedingly fine; and was encumbered with but
little timber, except immediately on the banks of the Missouri. They
found delicious plums, grapes, and blue currants. The musquitoes, and
other insects which here abounded, seem, however, to have occasioned
them some inconvenience.

On the 29th they were joined by five chiefs and seventy men of the
_Yanktons_, a tribe belonging to the Sioux Indians. The camps or huts of
this people are of a conical form: they are covered with buffalo robes,
painted with various figures and colours, and have an aperture at the
top for the smoke to pass through. Each hut is calculated to contain
from ten to fifteen persons, and the interior arrangement is compact and
handsome: the kitchen or place for cooking is always detached. Captain
Lewis delivered to these people a speech containing, as he says, the
usual advice and counsel with regard to their future conduct towards the
government and the "great father" (as the Indians are taught to call the
president) of the United States. He gave to the grand chief a flag, a
medal, a certificate, a laced uniform coat of the United States
artillery corps, a cocked hat and a red feather; and to the other chiefs
medals, tobacco, and clothing. Among the infer