Vlll PREFACE. 



In the preparation of this edition, I am largely indebted to many- 

 scientific friends : in the first place, to all workers in the department, 

 through the land, whose published results have made the edition a 

 necessity, and from whose works I have freely taken facts and con- 

 clusions, with due acknowledgment ; also, for personal aid, to the able 

 paleontologist, F. B. Meek, to whom the country owes a world of 

 gratitude for his labors ; to O. C. Marsh, for facts connected with 

 the Vertebrate life # of the American Cretaceous and Tertiary; to A. 

 H. Worthen, Director of the Geological Survey of Illinois, from 

 whom the volume has received several of its illustrations ; to L. Les- 

 quereux, for information with regard to fossil plants ; to James 

 Hall, the eminent paleontologist of New York ; to J. S. Newberry, 

 Chief Geologist of the State of Ohio ; to A. Winchell, formerly 

 State Geologist of Michigan, and now Chancellor of the Syracuse 

 University ; to G. K. Gilbert, Geologist of the Explorations under G. 

 M. Wheeler, First Lieutenant of Engineers, U. S. A. ; to J. Col- 

 lett, of the Indiana Geological Survey ; to J. Knapp, of Louis- 

 ville, Kentucky ; to G. C. Broadhead, State Geologist of Missouri ; 

 to J. W. Dawson, Principal of McGill University, Montreal ; to 

 E. Billings, of the Canadian Geological Survey, and one of the 

 best workers among fossils on the continent ; to S. W. Johnson, Pro- 

 fessor of Agricultural and Analytical Chemistry, for information on 

 chemical subjects ; to the Zoologist, A. E. Verrill, for the revision of 

 the zoological pages ; to F. V. Hayden, Geologist in charge of the 

 " Geological Survey of the Territories," for information pertaining to 

 the Geysers and the geological structure of the Rocky Mountain re- 

 gion ; and, through Dr. Hayden, to ,W. H. Holmes, his artist, for 

 drawings of geological scenes in the mountains ; to James T. Gard- 

 ner, Geographer in Surveys of the Territories, for facts with regard 

 to the topographical features of the summit region and the western 

 slope of the Rocky Mountains ; and to G. W. Hawes, assistant in the 

 Sheffield Scientific School, for analyses of plants, bearing on the ques- 

 tion of the origin of coal. 



To F. H. Bradley, I am under still greater obligations. For 

 the work, besides having had the benefit of his careful and untiring 

 labor in the revision of the proofs, has profited in various parts by 

 his extensive knowledge of American Geology, rendered thorough and 

 critical by personal investigations in several of the States and Terri- 

 tories. 



New Haven, Conn., March 1, 1874. 



