River Development as by the Rivers of North America (Paperback)

Purchase of this book includes free trial access to www.million-books.com where you can read more than a million books for free. This is an OCR edition with typos. Excerpt from book: CHAPTER II LAWS GOVERNING THE STREAMS THE water which flows off from the land, as is well known, is supplied by the condensation of vapour in the air. A part of the water reaching the earth flows over the surface and gathers into rills which unite to form larger streams, and a part sinks below the surface and, after following an underground course, usually by percolation through porous soil or rocks, emerges in springs, many of which join the surface flow. It is also well known that streams ranging in size from the smallest rills to the mightiest rivers are engaged either occasionally, as during floods, or continually, in carrying away material that was previously a portion of the land. The manner in which this material is acquired by the streams, the way it is transported, the effects it has on the flow of the streams, and on their bottoms and sides, the modifications in the configuration of the surface of the land due to the removal and re-deposition of debris, etc., are all phenomena that obey definite laws and are variously modified by conditions. If one can ascertain the laws governing the behaviour of a single stream, they should also apply not only to the streams of North America, but to those of all land areas. Plate I. Fig. A. Marion River, Adirondacks, New Vork. Summer stage, showing stones which are moved during high-water. (Photograph by S. R. Stoddard.) Fig. B. Ingall's Creek, Washington. Showing boulders too large for the stream to move even during high-water stages. No one stream, perhaps, in the limited time that an individual student is enabled to examine it, will furnish illustrations of all of the modifying conditions influencing the life of a great river. By selecting typical examples, however, affected by different modifying conditions, w...