PREFACE 



This volume is an abbreviation and simplification of COLLEGE 

 GEOLOGY, published five years ago. Many technical details have 

 been omitted, but the general purpose and scope of the volume is 

 not altered fundamentally. It is intended to present an outline 

 of the essential features of geology with as few technicalities as 

 the nature of the subject permits. Part I deals with geological 

 processes, and with the materials on which they operate, while the 

 theme of Part II is historical geology. The effort has been to treat 

 these topics in such a way as to give the student not merely an 

 understanding of the subject, but also an understanding of the 

 means by which the present status of the science has been reached. 



The theoretical and interpretative elements which enter into 

 the general conceptions of geology have been used freely, because 

 they are regarded as an essential part of the evolution of the science, 

 since they often help to clear and complete conceptions and to stim- 

 ulate thought. The aim has been, however, to characterize hypo- 

 thetical elements as such, and to avoid confusing the interpreta- 

 tions based on hypothesis with the statements of fact and estab- 

 lished doctrines. 



In many cases the topics discussed will be found to be pre- 

 sented in ways differing widely 'from those which have become 

 familiar. In some cases, fundamentally new conceptions of familiar 

 subjects are involved; in others, topics not usually discussed in 

 text-books are stated with some fullness; and in still others, the 

 emphasis is laid on points which have not commonly been brought 

 into prominence. Whether the authors have been wise in depart- 

 ing to this extent from beaten paths, the users of the volume must 

 decide. 



The University of Chicago, 

 February, 1914. 



