In conformity with this arrangement, Capt. Lewis, under the guidance of friendly Indians, crossed the mountains by a route which led him, after travelling one hundred and four miles, to Medicine River, and by that river to the Missouri. He reached the falls of the Missouri on the 17th of July, and leaving there a portion of his party, under Sergt. Gass, to make preparations for transporting their baggage and canoes round the falls, set out, accompanied by Drewyer and the two brothers Fields, with six horses, to explore Maria's River, to ascertain its extent toward the north. From the 18th to the 26th, they were engaged in this exploration. On the eve of their return, an event occurred, which, being the only instance in which the expedition was engaged in any conflict with the Indians with loss of life, requires to be particularly related. CONFLICT WITH THE INDIANS. We were passing through a region frequented by the Minnetarees, a band of Indians noted for their thievish propensities and unfriendly dispositions. Capt. Lewis was therefore desirous to avoid meeting with them. Drewyer had been sent out for game, and Capt. Lewis ascended a hill to look over the country. Scarcely had he reached the top, when he saw, about a mile on his left, a collection of about thirty horses. By the aid of his spy-glass, he discovered that one-half of the horses were saddled, and that, on the eminence above the horses, several Indians were looking down towards the river, probably at Drewyer. This was a most unwelcome sight. Their probable numbers rendered any contest with them of doubtful issue. To attempt to escape would only invite pursuit; and our horses were so bad, that we must certainly be overtaken: besides which, Drewyer could not yet be aware that Indians were near; and, if we ran, he would most probably be sacrificed. We therefore determined to make the best of our situation, and advance towards them in a friendly manner. The flag which we had brought in case of such an emergency was therefore displayed, and we continued slowly our march towards them. Their whole attention was so engaged by Drewyer, that they did not immediately discover us. As soon as they did so, they appeared to be much alarmed, and ran about in confusion. When we came within a quarter of a mile, one of the Indians mounted, and rode towards us. When within a hundred paces of us, he halted; and Capt. Lewis, who had alighted to receive him, held out his hand, and beckoned him to approach: but he only looked at us, and then, without saying a word, returned to his companions. The whole party now descended the hill, and rode towards us. As yet we saw only eight, but presumed that there must be more behind, as there were several more horses saddled. Capt. Lewis had with him but two men; and he told them his fears that these were Indians of the Minnetaree tribe, and that they would attempt to rob us, and advised them to be on the alert, should there appear any disposition to attack us.