opening a Highway to the Pacific 57
face with the most serious problem encountered during the journey. The western slope of the Rockies differed greatly from the eastern in being much, more rugged and precipitous, with deep caiions through ^\•hich the rivers rushed and swirled for great distances, until finally, on emerging from the mountains, they became navigable for boats. The travellers had Ijeen able to ascend the Missouri, to its source, with comparative ease, following along the river valley which usually was free from serious obstructions, a plain and easy path, sloping so gradually that it appeared to be almost level. Now they must make their way over sharp ridges, through terrific mountain defiles, choked with fallen timber and masses of rock debris. Moreover, they had no satisfactory way of determining what route to take, or how far they would be obliged to travel before reaching navigable water. It was necessary to follow the advice of their Shoshone friends to some extent, but the leaders soon found that this could not be relied upon altogether.
Clark discovers and names Lewis River. As a preparatory step. Captain Clark explored a way down Salmon River to its junction with a larger river to which he gave the name of his friend Lewis. ^ But he learned that this stream was unnavigable for many miles below the point reached, and that it would be impossible to follow its course through the cailon. He therefore returned, and the explorers decided to cross over to the river which flowed northward (Clark's
^ It is now commonly called "Snake Rivev."
