Page:Popular Science Monthly Volume 4.djvu/389

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375
LITERARY NOTICES.

governments, both State and national. It has been held by some that the removal of forests causes an actual lessening of the annual rainfall; but this view is hardly borne out by recorded observations. The same injury, however, is equally accomplished in a somewhat different way. The removal of timber lays the ground open to rapid evaporation, and, worse still, causes the surface covering of earth, mould, etc., to be washed away from the unprotected sides of hills and mountains. The consequence is that the same yearly amount of moisture, instead of being slowly and gradually discharged by the brooks and streams, rushes away in destructive torrents and freshets, such as are all too familiar every spring, when the winter's snow is melting. The water-supply being thus lost all at once, the steady streams and rivers of a generation or two past dwindle in the summer to fitful and worthless rills. Such is the harvest of disaster from "our great lumbering interest."

Chapter III., on the "Geological Relations of Ohio," is yet more interesting in a purely scientific aspect. It begins with a brief outline of the characteristic features of the several great periods of geological history, as represented by the deposits in North America. Here Dr. Newberry gives, in a popular form, the gist of his discussion lately presented to the American Association of Science at Portland, and more recently to the National Academy of Arts and Sciences, at its session in this city in October last, on "Cycles of Deposition in Sedimentary Rocks," a generalization unsurpassed for its beauty, its simplicity, its wide-reaching grasp, and its lucid explanation of a multitude of details, previously insignificant and often wearisome.

Each of the great ages of palæozoic geology—the two Silurians, the Devonian, and the Carboniferous—represents, in this view, a grand invasion of the sea upon the land, slowly spreading itself over the continent, mainly from the west and south, and laying down a series of sediments in a fixed and regular order, depending on the increasing depth of the advancing waters. No one, it would seem, can look at the facts in a broad and philosophical view, excluding of course the thousand details which cause partial modifications in every such great operation of Nature, without recognizing here a new light cast upon the hitherto unmeaning succession of varying kinds of deposits.

The remainder of this volume is occupied with the detailed description of the geology of twenty-one counties—nearly one-fourth of the State—by Profs. Andrews and Orton, Dr. Newberry, and Messrs. M. C. Read, G. K. Gilbert, and N. H. Winchell, assistants. While all these accounts are full of valuable matter, especial interest attaches to Prof. Orton's excellent account of the lower Silurian formation, known in Ohio as the Cincinnati Group, and to Mr. Gilbert's summary of the surface geology of the Maumee Valley, which is rich in remarkable illustrations of the effects of the great sheet of ice, and afterward of the broad expanse of water, which overspread so much of our northern country during the several parts of the great Glacial Epoch. Dr. Newberry's sketch of Cuyahoga County, the region around Cleveland, also treats of the same fascinating subject; and Prof. Andrews gives quite a chapter of "Conclusions, Theoretical and Practical," on the mode of formation of different varieties of coals.

It only remains to refer briefly to the second volume or second part of Volume I., which treats of the paleontology of Ohio. This work, somewhat larger than the first part, comprises three divisions, as follows: the "Invertebrate Fossils of the Silurian and Devonian Formations," by Prof. F. B. Meek; the "Fossil Fishes of the Devonian Group," by Dr. Newberry; and the "Fossil Plants of the Coal Period" (in part), also by Dr. Newberry. With the exception of these last, the present volume includes only the fossils below the carboniferous rocks.

In these chapters, a great and permanent work has been accomplished for science, in the accurate description and classification of a very large number of interesting fossils, heretofore either undescribed, or described so imperfectly as not to be reliable as a basis for study. The crinoids, mollusks, brachiopods, and trilobites, have been well intrusted to Mr. Meek, whose full and careful discussions are accompanied with an admirable series of plates.