LITERARY NOTICES. 



375 



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 accom- 

 plished 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 conse- 

 quence is that the same yearly amount of 

 moisture, instead of being slowly and gradu- 

 ally 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 sum- 

 mer to fitful and worthless rills. Such is 

 the harvest of disaster from " our great 

 lumbering interest." 



Chapter III., on the " Geological Rela- 

 tions 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 discus- 

 sion lately presented to the American As- 

 sociation 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 un- 

 surpassed for its beauty, its simplicity, its 

 wide-reaching grasp, and its lucid explana- 

 tion of a multitude of details, previously in- 

 significant and often wearisome. 



Each of the great ages of palaeozoic ge- 

 ology — 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 op- 

 eration of Nature, without recognizing here 

 a new light cast upon the hitherto unmean- 

 ing succession of varying kinds of deposits. 



The remainder of this volume is occu- 

 pied 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 at- 

 taches to Prof. Orton's excellent account 

 of the lower Silurian formation, known in 

 Ohio as the Cincinnati Group, and to Mr. Gil- 

 bert's summary of the surface geology of 

 the Maumee "Valley, which is rich in re- 

 markable 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 " Conclu- 

 sions, 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 Eossils 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. New- 

 berry. With the exception of these last, the 

 present volume includes only the fossils be- 

 low the carboniferous rocks. 



In these chapters, a great and perma- 

 nent work has been accomplished for sci- 

 ence, in the accurate description and clas- 

 sification of a very large number of in- 

 teresting fossils, heretofore either unde- 

 scribed, or described so imperfectly as not 

 to be reliable as a basis for study. The 

 crinoids, mollusks, brachiopods, and trilo- 

 bites, have been well intrusted to Mr. Meek, 

 whose full and careful discussions are ac- 

 companied with an admirable series of 

 plates. 



