The party, continuing indefatigable in their exertions, dragged the canoes, or pushed them along with poles, up the current of the Missouri. This they did, day after day, until the 27th of June, when they arrived at the _Three forks of the river_; that is, at the point at which three rivers, each of considerable size, flow together, and form the great stream. As it was difficult to determine the largest of the three, Captains Lewis and Clarke decided on discontinuing here the appellation of Missouri; and named the streams, respectively, Jefferson's, Madison's, and Gallatin's river. As the first of these flowed from the west, they ascended it in preference to the others; but they continued to experience great difficulty with the canoes, in consequence of the rapidity of the current. They were now approaching the termination of the first great division of their journey. The river continued to lessen as they proceeded: its width, in the part at which they arrived on the 8th of July, was not more than forty yards; and, on the 11th, it was diminished to twelve, so as to admit of being waded over without hazard. They had now proceeded, by computation, three thousand miles from the mouth of the Missouri; and they, not long afterwards, reached its extreme navigable point, in latitude 43 degrees 30 minutes, and nearly in longitude 112 degrees west from Greenwich. Here they laid up their canoes, until they should return from the Pacific ocean; and, proceeding by land, had the gratification of tracing the current to its _fountain head_, in the midst of the Rocky Mountains. Seventeenth Day's Instruction. WESTERN TERRITORY CONTINUED. _Narrative of_ LEWIS _and_ CLARKE'S _Travels from the Source of the Missouri to the Pacific Ocean._ From the source of the Missouri, we will now accompany these gentlemen in their journey across the Rocky Mountains, and in their subsequent navigation of the Oregan or Columbia to the Pacific Ocean. They had reached the highest ground in the _Rocky Mountains_, or that elevated part of the continent which constitutes the boundary between the streams flowing to the Atlantic on the one side, and the Pacific on the other. Their next object was to prosecute their journey westward, through this cold and barren track, until they should come to a navigable stream flowing into the Columbia, the great channel of access to the western ocean. They had been told, by Indians in the Mandan country, that, immediately on crossing the central ridge, they would discover copious rivers running in a direction towards the Columbia. Captain Lewis accordingly found a clear stream forty yards wide, and three feet deep, which ran towards the west. It was bounded on each side by a range of high mountains, and was so closely confined between them, as not only to be unnavigable, but to be impassable along its banks. A still more discouraging circumstance was the total want, in this wintry region, of timber fit for building canoes.