GEOLOGY 



PART I 



THE MATERIALS OF THE EARTH AND 

 PEOCESSES WHICH AFFECT THEM 



CHAPTER I 

 PRELIMINARY OUTLINE 



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

 It treats of rocks and of the agencies and processes which have 

 been involved in their formation, and from the rocks and their 

 structures it attempts to make out the various stages through 

 which the earth and the living things which have dwelt upon it 

 have passed. It is one of the broadest of the sciences, and brings 

 under consideration certain phases of other sciences, particularly 

 astronomy, physics, chemistry, zoology, and botany. 

 ^ Subdivisions. So broad a science has many subdivisions. 

 That phase which treats of the outer relations of the earth is Cosmic 

 or Astronomic Geology; that which treats of the constituent parts 

 of the earth and its material is Geognosy, of which the most impor- 

 tant branch is Petrology, the science of rocks. That phase which 

 deals with the structural arrangement of the rocks is Geotectonic, 

 or Structural Geology; that which deals with the forces involved 

 in geologic processes is Dynamic Geology; that which treats of the 

 face of the earth, or topographic form, is Physiographic Geology; 

 that which concerns itself with the fossils that have been preserved 

 in the rocks, and with the faunas and floras that have lived in the 

 past, constitutes Paleontologic Geology, or Paleontology. The treat- 

 ment of the succession of events is Historical Geology, which is 



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