PREFACE 



In the preparation of this book, an attempt has been made to pre- 

 sent an outline of the essentials of modern geology. By avoiding 

 all details not necessary to an understanding of the fundamental 

 principles of the science, it is hoped that this work will prove inter- 

 esting to the student, although not less accurate because interesting. 

 In the section on physical geology the human relation has been 

 emphasized whenever possible, while in the historical section the 

 history of life from the evolutionist's point of view has been taken 

 up in broad outline. 



Much that may prove excellent in this work is due to the help of a 

 number of eminent geologists, whose suggestions and criticisms have 

 added many interesting points and have assisted in the elimination 

 of errors. 



The writer wishes especially to express his debt to Dr. W. D. Mat- 

 thew, of the American Museum of Natural History, City of New 

 York; to Professor Joseph Barrell, of Yale University; and to 

 Professor A. W. Grabau, of Columbia University, upon whom he has 

 freely called for suggestions and criticisms and from whom much 

 valuable assistance has been received. 



One or more chapters have also been read and helpfully criticized 

 by the following geologists and educators, and their generous aid 

 is acknowledged with keen appreciation : Messrs. H. E. Gregory, of 

 Yale University; C. K. Schwartz, of Johns Hopkins University; 

 J. B. Woodworth, of Harvard University; J. S. Grasty, of the Uni- 

 versity of Virginia ; N. M. Fenneman, of the University of Cincin- 

 nati; Sumner W. Cushing, of the Salem (Massachusetts) Normal 

 School; J. W. Gidley and C. W. Gilmore, of the United States 

 National Museum ; T. W. Stanton and F. H. Knowlton, of the 

 United States Geological Survey; Charles Schuchert and G. G. Mac- 

 Curdy, of Yale University ; T. D. A. Cockerell, of Boulder, Colorado ; 

 L. Hussakof, of the American Museum of Natural History; 

 E. C. Case, of the University of Michigan; O. P. Hay, of the Carnegie 



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