Valleys

Valleys, low-lying or hollow tracts on the earth's surface between mountains or elevated ground. They are generally parallel to the direction of the ridges; but some are transverse, cutting through mountain-chains. As a rule they have a watercourse at or near their lowest level. The origin of valleys and their growth are dealt with in numerous articles in this work: see EARTH (Vol. IV. p. 164), DENUDATION, GEOLOGY (Vol. V. p. 149), MOUNTAINS, LAKE, and especially RIVER; besides those on notable valleys, as that of the Colorado, Yosemite, &c., and the mountain-systems which enclose such—Alps, Appalachians, &c.