136 ' NINTH REPORT. 



GEOLOGY AND PHYSICAL GEOGRAPHY OF MICHIGAN. 

 W. F. Cooper, Michigan Geological Survey. 

 CONTENTS. 



Introduction. Geology and Physical Geography defined; correlations. 



Michigan Geological Survey. 



Winehell's Diagonal System. 



Origin of Great Lake Basins. 



Area and Elevation of Michigan, Pre-glacial Drainage. 



Pre-glacial Rainfall. 



Tilting of Great Lake Basins, Shore- Lines, Willow}' Drainage. 



Terraces. 



Temperature. 



INTRODUCTION. GEOLOGY AND PHYSICAL GEOGRAPHY DEFINED. CORRE- 

 LATIONS. 



Geology has been variously defined as the physical history of the earth 

 and its inhabitants, as recorded in its structure. It includes an account of 

 the changes through which they have passed, the laws of these changes, 

 and their causes. In a word, it is the history of the evolution of the earth 

 and its inhabitants ^ In a later work we have geology defined as that science 

 which treats "of the structure of the earth, of the various stages through 

 which it has passed, and of the living beings that have dwelt upon it, to- 

 gether with the agencies and processes involved in the changes it has under- 

 gone. Geology is essentially a history of the earth and its inhabitants. "^ 



On the other hand physical geography is defined as that "branch of 

 geography that treats of the physical features of the earth, more especially 

 those of its surface, including the operation of existing physical agencies, 

 the distribution and flow of water, and the distribution of the forms of 

 animal and plant life.'^^ Again in this connection we have the subject of 

 physiographic geology, "a general study of the existing features of the 

 earth's surface, as contours of continents and systems of surface relief, par- 

 tially synonymous with physical geography, but dealing with general physical 

 features as resultants of past dynamical agencies, while physical geography 

 deals with details, chiefly as existing under recent or present dynamical 

 forces."^ As treated in this paper I will combine certain phases of both 

 subjects as given in this and the former definition, eliminating any consider- 

 ation of the distribution of the forms of plant and animal life. 



The principal departments of the science of geology may be divided into 

 structural geology, • historical geology or the treatment of the succession 

 of events, while stratigraphic geology deals with the succession of beds laid 



1 Joseph Le Conte, "Elements of Geology", 1896, p. 1. 



2 Chamberlin & Salisbury, "Geology", Volumn I, p. 1 . 



3 Standard Dictionary. 



4 Standard Dictionary. 



