Early in April, Lewis and Clark, with thirty men in their canoes, resumed their voyage. Their course was nearly west. In May they reached the mouth of the Yellow Stone river, and on the 13th of June came to the _Great Falls of the Missouri_. Here they found a series of cataracts ten miles in length. At one spot the river plunged over a precipice eighty-seven feet in height. Carrying their canoes around these falls, they re-embarked, and paddled through what they called "The Gates of the Rocky Mountains." Here for six miles they were in a narrow channel with perpendicular walls of rock, rising on both sides to the height of twelve hundred feet. Thus these adventurers continued their voyage till they reached the head of navigation, three thousand miles from the mouth of the Missouri river. Passing through the mountains they launched their canoes on streams flowing to the west, through which they entered the Columbia river, reaching its mouth, through a thousand perils on the 15th of November. They were now more than four thousand miles distant from the mouth of the Missouri. Such was the breadth of the estate we had purchased of France. Here they passed their second winter. In the early spring they commenced their return. When they arrived at the Falls of the Missouri they encountered a numerous band of Indians, very bold and daring, called the Blackfoot. These savages were astonished beyond measure, at the effect of the rifle which could emit thunder and lightning, and a deadly though invisible bolt. Some of the boldest endeavored to wrench the rifles from some of the Americans. Mr. Lewis found it necessary to shoot one of them before they would desist. The rest fled in dismay, but burning with the desire for revenge. The explorers continuing their voyage arrived at Saint Louis on the 23rd of September, 1806, having been absent more than two years, and having traveled more than nine thousand miles. When the expedition, on its return, had reached the head waters of the Missouri, two of these fearless men, Colter and Potts, decided to remain in the wilderness to hunt beaver. Being well aware of the hostility of the Blackfoot Indians, within whose regions they were, they set their traps at night, and took them up in the first dawn of the day. Early one morning, they were ascending a creek in a canoe, visiting their traps, when they were alarmed by a great noise, like the trampling of animals. They could see nothing, as the perpendicular banks of the river impeded their view. Yet they hoped that the noise was occasioned simply by the rush of a herd of buffaloes.