tends through Idaho, Montana, Wyoming, Colorado, and New Mexico, and sends some outlying ridges into Texas. See Rocky Mountains.
The Colorado Plateaus. West of the Rocky Mountains, in Wyoming, Colorado, Utah, New Mexico, and Arizona, is the basin of the Colorado River. This great stream confines its drainage, save near its mouth, to an upland several thousand feet above the sea. Having abundant sources in the rains and snows of the various parts of the Rocky Mountain Range, and rising at great altitudes, it has both velocity and volume, and hence has cut out the great cañons for which it is famous. This is a deeply but only partly dissected region consisting of blocks of strata, cut apart from each other by profound gorges, often intricate in pattern. Being an arid region, the abundant waters are of remote derivation and sunk in the cañons, while the sparse rainfall causes desert conditions to be general, with much exposed rock, little vegetation, and a general absence of conditions favorable to civilized life. Closely associated with these great plateaus are two short but lofty ranges of mountains. One of these is the Wasatch, marking the boundary between the plateaus and the Great Basin, in central Utah. The other is the Uinta Range, about loO miles in length, and extending from northwestern Colorado through the borderlands of Wyoming and Utah. Its chief development is in the latter State and in its east and west trend it departs from the usual direction of American mountain axes.
The Great Basin. This is an area of interior drainage, made up of many minor basins, of which the chief is that of the Great Salt Lake in Utah. See Great Basin.
The Columbia and Snake River Plateaus. Large areas drained by these streams in Idaho, Oregon, and Washington are of volcanic origin, and along the Snake River in Idaho and Oregon the lavas form plateaus about 4000 feet in altitude. They are a natural desert, since the region is arid, but are capable of great development under the process of irrigation.
The Mountains and Valleys of the Pacific Coast. The features to which reference is here made belong to three States: California, Oregon, and Washington. They will be best understood if it is observed that a single lofty range, the Sierra Nevada, forms the eastern border of California, and that it extends, under the name of the Cascade Range, northward through central Oregon and Washington. Its culminating point, in California, is seemingly Mount Whitney (14,500-15,000 feet), which may also be the culminating point of the entire United States south of Alaska. Bordering the sea are lower and younger mountains, constituting also a prolonged range, but variously named, as the Coast Range in California, the Klamath Mountains in Oregon, and the Olympic Mountains in Washington. (See Sierra Nevada; Cascade Range, etc.) Between these parallel ranges are lowland valleys of the utmost importance in the development of the region. In California there is the great valley drained by the Sacramento and Joaquin rivers, the centre of the fruit and grain culture of the State. In Oregon the Willamette Valley is analogous in origin and in human importance to this, as still farther north there is the Puget Sound Valley in the State of Washington. In association with these mountain ranges, reference should be made to the giant and minor volcanic cones which line their trend, and many of whose well-formed summits rise high into the snow-line (Shasta, Hood, Rainier, Baker). The coast line of the Pacific is not nearly so great as that of the Atlantic coast, because it is less indented. It has, however, a few of the choicest bodies of inland or protected waters to be found on any shore. Such are San Francisco Bay and Puget Sound, while the deep, tidal Columbia and Willamette rivers offer similar advantages to northern Oregon. It is thus seen that the Cordilleran system is made up of several parallel ranges of mountains, separated in turn by intermontane areas of lofty plateau, or, nearer Pacific Ocean, by broad and fertile lowlands.
Hydrography. The drainage of the United States may be classed as Atlantic and Pacific. As with the entire continent, and with South America, the smaller ocean receives by far the greater contribution of fresh water from the lands now under review. The Atlantic streams may be considered as belonging to the Hudson Bay, the Gulf, or to open sea drainage. With unimportant exceptions farther west, the Red River of the North carries the contribution of the United States area to Hudson Bay waters. The open sea streams are all of moderate length and volume except the Saint Lawrence, which should be viewed as rising in Minnesota, although locally expanded into lakes of exceptional size. (For details concerning these bodies of water, the reader is referred to the article Great Lakes.) All the streams which enter the lakes from the United States are relatively small. Their courses are short, which is equal to saying that the line of water partings between the Laurentian and Mississippi basins is close to the lakes. The divide is also nearly everywhere quite inconspicuous. The streams have thus small capacity for transporting land waste into the lakes. Such waste as reaches the lakes rests in them, a condition from which results the exceeding clearness of Niagara, or of the Saint Lawrence waters that pass the Thousand Islands.
The open Atlantic streams, draining that part of the country which is historically oldest, and being often tidal, have a fame and a commercial value out of all proportion to their size. To begin with the rivers of New England, its conspicuous streams, the Penobscot, Kennebec, Merrimac, Connecticut, and Housatonic, are most of them entered by the tides for many miles. The Merrimac and Connecticut, above tide water, are types of many New England rivers which are interrupted by rapids due to glacial blockade, thus furnishing a great store of water power.
New York is composite in drainage. The Hudson, with the Mohawk, drains much of its central and eastern lands, but is chiefly important for its tidal course of 150 miles, with great harborage at its mouth, and an open gateway to the west from the head of tide water. The Genesee, Black, and other rivers carry to the Saint Lawrence much of the run-off of northern and western New York. The Susquehanna, the Delaware, and the Mississippi take nearly all the remainder of New York waters. In a most anomalous manner, due to glacial change of slope, the Allegheny gathers for the Gulf of Mexico waters that fall within a few miles of Lake Erie.
