A text-book of physiography, or physical geography; being an introduction to the study of the physical phenomena of our globe - Softcover

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1888 Excerpt: ... The Grand Canon of the Colorado River is 300 miles in length, and in some places more than 6,0oo feet in depth. On either side the palaeozoic strata rise in vertical walls, separated by terraces, up to the level of the plateausurface, and, at the mouth of the canon, break away on either hand in a grand mural escarpment. For the formation of this and other canons it is required that the river by whose action the channel has been eroded should have its source in a region beyond the canon, and that the region through which the channel is cut should be almost rainless. Such is the case with the Colorado River, which has its source high up amongst the Rocky Mountains. Were rain and river action general over the surface of the plateau, the banks would be worn down into slopes, and the gorge-like character of the channels would be destroyed. It is probable, however, that the canons of the Colorado region were originally excavated at a period when the present streams were larger and more effective than at present. Some of the eroded valleys are now dry; and in others the present streams are but miniature representatives of those which formerly flowed in their channels. Johnston's School Physical Atlas. G.--Transporting Power Of Rivers. The transporting power of rivers depends on three conditions:--Dr. J. S. Newbury, Geological Report, Colorado Explor. Expedition, under Lieut. Ives," p. 42, (1861). J. W. Powell, Exploration of the Colorado River, &c, (1875.) Capt. C. E. Dutton, Tertiary History of the Grand Canon District, with Atlas, (1882.) (1.) The volume and velocity and the current. (2.) The size, shape, and specific gravity of the matter to be moved; and (3.) The chemical composition of the water; saline waters being more buoyant than very pure or fr...