Page:Popular Science Monthly Volume 55.djvu/138
THE POPULAR SCIENCE MONTHLY.
may revolutionize the topographical conditions and produce climatic and physical changes. All these characteristics of rivers are systematically and comprehensively set forth in Mr, Russell's book, where the life-history of the stream is presented, from its beginning in a little mountain torrent or hillside rill, through its course as it descends to the plain, wearing and tearing and deepening its channel. In the plain its character and action are modified under the new conditions in which it finds itself, and gradually, as it approaches its mouth, it deposits, whereas it had torn away at its beginning, and shows contrasts quite as marked as those between youth and old age. Rivers have their growth in time, too, and a stream that has been carrying on its work for long ages presents different characteristics throughout its course from one that comes fresh to its task, and these differences are pointed out. We are told, too, how rivers grow, drawing new affluents to themselves and extending their sources backward, and how when the sources of streams on different sides of a watershed approach on the summit, there is a struggle for the mastery. These are only a few of the new suggestions which the book offers us. Coming to the more matter-of-fact details, the laws governing streams and their course; the influence of inequalities and the hardness of rocks, especially on riverside scenery; and the office of rivers as carriers of material in suspension and in solution, are considered; then their deposits, under various heads and aspects, and the effects of changes in the elevation of the land, of variations in the load of material and of changes of climate upon them; the origin and characteristics of stream terraces and stream development, the topics concerning which are too many and varied to bear more than a passing reference. The more salient characteristics of American rivers are discussed as to the nine drainage slopes—the Atlantic, St. Lawrence, Hudson Bay, Arctic, Bering, Pacific, Great Basin, Gulf, and Caribbean—each slope presenting its own general characteristics, with varieties in detail almost as numerous as the rivers. The whole is briefly summarized in the last chapter. The Life History of a River. We have given merely the tamest inventory of only a part of the topics of Mr. Russell's book. As the subject is treated by the author with careful attention to specific features, as the magnitude of our river systems is indicated, and as rivers with different or contrasting characteristics—the St. Lawrence and the Colorado, for example—are compared with one another, the subject takes on an aspect that is really grand.
- The Structure and Classification of Birds. By Frank E. Beddard. London and New York: Longmans, Green & Co. Pp. 548.