PREFACE 



Two reasons have led the author to give this Manual its American 

 character : first, a desire to adapt it to the wants of American stu- 

 dents ; and, secondly, a belief that American Geological History, on 

 account of the peculiar simplicity and unity of the system of progress, 

 affords the best basis for a text-book of the science. North America 

 stands alone in the ocean, a simple isolated individual continent, 

 even South America lying to the eastward of its meridians ; and, con- 

 sequently, the laws and agencies of progress have been undisturbed 

 by conflicting conditions and movements in other lands. The author 

 has, therefore, written out North American Geology by itself, and 

 drawn the chief illustrations of continental development from its rec- 

 ords. Facts from other continents, however, have been freely added, 

 because required, both to give completeness to the treatise, and to 

 exhibit. the comprehensiveness of geological principles. The aim has 

 been to present for study the successive phases in the History of 

 the Earth ; that is, of its Continents, its Seas, its Climates, its Life, 

 and of all its various characteristics, and not a mere series of facts 

 about rocks and their dead fossils. 



The author has endeavored to bring the volume into as small a 

 compass as consistent with a proper exhibition of the science ; and, 

 if some find its pages too numerous, he feels confident that quite as 

 many would prefer greater fullness. The details introduced have 

 seemed to be necessary, in order that the march of events should be 

 appreciated. At the same time, the work has been adapted to the 

 general reader and literary student, by the printing of the scientific 

 details in finer type. The convenience of a literary class has been 

 further provided for by adding to the Appendix a brief synopsis of 

 the part in coarser type, in which each head is made to present a 

 subject, or question, for special attention. And, as many may not be 

 familiar with the science of Zoology, a review of the classification of 

 animals, with numerous figures, has been inserted as an introduction 

 to the Historical part of the Manual. 



The illustrations of American Paleozoic life have been largely 



