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 inferior men were distributed knives, tobacco, bells, tape, binding, and other articles of trifling value. After this the Indian chiefs, and Captains Lewis and Clarke, smoked together the pipes of peace. These chiefs begged the strangers to have pity on them, as they were very poor; to send traders to them, as they wanted powder and ball: they were also anxious to be supplied with some of "the great father's milk," by which they meant rum, or other ardent spirits. This people are stout and well proportioned, and have a peculiar air of dignity and boldness: they are fond of decorations, and use, for this purpose, paint, porcupine-quills, and feathers. Some of them wear a kind of necklace of white bear's claws, three inches long,