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SCRIBNER'S MAGAZINE.

VOL. IV.

AUGUST, 1888.

No. 2.

RIVERS AND VALLEYS.

By N. S. Shaler.

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HE greater part of the facts with which geologists have to deal possess for the general public a recondite character. They concern things which are not within the limits of familiar experience. In treating of them, the science uses a language of its own, an argot as special as that of the anatomist or the metaphysician. There is, however, one branch of the subject the matter of which demands no special knowledge for its understanding, viz.: the surface of the earth. At first, geologists were little inclined to deal with the part of their field which is visited by the sun. Gradually, however, they have come to see that this outer face of the earth is not only a kindlier but a more legible part of the great stone book, and they have made a division of their work which they entitle Surface Geology. In this division they include all that is evident to the untrained understanding, the contour of land and of sea floor, the aspects of shores, the conditions of soil, etc. Under the head of Rivers and Valleys we propose to consider one division of this simple but ample division of geologic science.

If the reader wishes to begin a series of studies of an unprofessional character which will lead him to some of the most important fields of knowledge which

the earth's science can open to him, he cannot do better than find his way to his subject through a river-valley. There are many advantages offered to him in beginning his inquiries in this pleasant way. In the first place, the outward aspect of the phenomena with which he has to deal is already familiar to him. We can all recall to mind some of these troughs of the earth through which flows a stream, be it mountaintorrent, brook, or river. The steep or gentle slopes of the valley toward the agent which has constructed it, the flowing water, as well as many of the important actions of the stream in its times of flood or in its cataracts, are also familiar. In fact, there is not a feature or a phenomenon visible in the valley which has not a popular name, indicating that it is a matter of common and unrecondite observation. Whoever will follow an ordinary stream from its sources to the sea in such a journey as he may make in a few days' travelling, and will avail himself of its teachings, with the aid of the simplest understandings derived from a knowledge of physical laws, will obtain a clue to a very large part of the earth's machinery.

To see the actual beginning of the river under the conditions which are best for our inquiry, we must observe the surface at some point on the dividing line between two streams where they head together, near the crest of a mountain, in a time of rain. All that is visible are the drops of rain which slip out of the leaden air and patter on the surface

Copyright, 1888, by Charles Scribner's Sons. All rights reserved.

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