INTERACTION OF THE SPHERES 19 



2. Hydrosphcric — 



a. by water currents. 



b. by ice, terminal moraines, etc. 



c. by snowslides, etc. 



3. Ccntrospheric — purely under the influence of gravi- 



tation. 



4. Biospheric — by man, and more rarely other ani- 



mals. 

 II. Chemical: In solution. 



1. Atmospheric — dissolved in air, as water-vapor, 



gases, etc. 



2. Hydrospheric — dissolved in water, c. g., salt. 



3. Pyrospheric — in igneous solution. 



4. Biospheric — as body constituents, etc. 



DEPOSITION. 



A. Mechanical. 



1. Atmospheric — by wind, etc. Atmoclastic and ane- 



moclastic deposits. 



2. Hydrospheric — by water. Hydroclastic deposits. 



3. Pyrospheric — by igneous action. Pyroclastic de- 



posits. 



4. Biospheric — by animals, including man. Bioclastic 



deposits. 



B. Chemical. 



1. Atmospheric — atmogenic deposits — snow, etc. 



2. Hydrospheric — hydrogenic deposits, salt, gypsum, 



etc. 



3. Pyrospheric — pyrogenic or igneous deposits. 



4. Biospheric — biogenic deposits (coral rock), etc. 



DEFINITION AND SUBDIVISIONS OF GEOLOGY. 



Geology is the science of the entire earth. The common im- 

 pression of the layman, that geology is the study of the lithosphere 

 alone, is a misconception, based on the fact that the geologist con- 

 cerns himself largely with the crust of the earth, since here he finds 

 the record of the history he seeks to read. According to the division 

 of the earth as a whole into a series of spheres, as already set forth, 

 we may divide the science of geology as a whole into the following 

 branches : 



