But civilization has demonstrated that they subserve a much higher purpose, that the rivers of a country are its great arteries and highways of trade, and that they fulfill functions as numerous and benign in the political economy as in the physical geography of the regions they furrow. In the Old World, the advancing streams of culture, science and commerce, and even the migrations of nations, have ebbed and flowed along the classic valleys of the Rhine, the Rhone and the Danube; and the banks of the Tigris, the Euphrates and the Nile are rich in memories of the world's mightiest and most splendid empires. In America the fertile watersheds of the Ohio, the Mississippi and the Missouri are fast becoming what their antitypes of the great continent have been in the past. The outspreading wave of civilization and population has already reached westward to the foot of the Rocky Mountains from the Gulf of Mexico to Montana and Idaho, while even the basin of the Columbia River is rapidly filling up with an active, thriving and busy people, who can smile at the poet's vision: Where rolls the Oregon, and hears no sound Save its own dashings. The water-courses of a country are not less valuable to it than the little Pactolus was to the ancient city of Sardis, through whose streets it ran freighted with gold. But these natural highways of human intercourse, like most of Nature's provisions, are capable of indefinite artificial extension and multiplication. Our finest modern canals are scarcely smaller, and certainly capable of more uninterrupted, safe and heavy navigation, than many of the rivers which have figured in history, and which Pascal so graphically described as "_moving roads_ that carry us whither we wish to go."