THE COMPILATION OF EARTH HISTORY 3 



being laid upon the processes in the former and upon the result- 

 ant features in the latter. 



Under dynamical geology are included important subdivisions, 

 such as seismic geology, or the study of earthquakes, and vul- 

 canology, or the study of volcanoes. Another large subject, 

 glacial geology, belongs within the broad frontier common to both 

 dynamical geology and physiography. A relatively new sub- 

 division of geological science is orientational geology, which is 

 concerned with the trend of earth features, and is closely related 

 both to physiography and to dynamical and structural geology. 



Tabular recapitulation. In a slightly different arrangement 

 from the above order of mention, the subdivisions of geology are 

 as follows : 



Subdivisions of Geology 



Petrographical Geology. Materials of the earth. 



Geotectonic Geology. Architecture of the earth's outer 



shell. 



Dynamical Geology. Earth processes. 



Seismic Geology earthquakes. 

 Vulcanology volcanoes . Glacial 

 Geology glaciers, etc. 

 Physiographical Geology. Earth physiognomy and its 



genesis. 



Orientational Geology. The arrangement and the trend 



of earth features. 



In one way or another all of the above subdivisions of geology 

 are in some way concerned in the genesis of earth physiognomy, 

 and they must therefore be given consideration in a work which 

 is devoted to a study of the meaning of earth features. The 

 compiled record of the rocks is, however, something quite apart 

 and without pertinence to the present work. As already indicated 

 its subdivisions are : 



Astronomic Geology. Planetary history of the earth. 



Statigraphic Geology. The pagination of earth records. 



Historical Geology. The compiled record and its inter- 



pretation. 

 Paleontological Geology. The evolution of life upon the earth. 



In every attempt at systematic arrangement difficulties are 

 encountered, usually because no one consideration can be used 

 throughout as the basis of classification. 



