GEOLOGY 



135 



throughout the whole of the earth's history, both its period 

 of growth, as well as that of decay. 



As a result of the interpretation made possible by the 

 doctrine of uniformitarianism, the processes, by which the 

 beds of sedimentary and igneous rocks which make up the 

 visible earth's crust are formed, are readily interpreted and 

 understood through the action of processes that we see going 

 on at the present time around us. We need no other doctrine 

 to account for them. Processes of rock decay, transportation, 

 and redeposition on the sea bottom, lake bottoms, and certain 

 parts of the land surface may be observed in operation. These 

 are processes that operate on the earth's surface and are open 

 to direct observation. 



This is not the case, however, with certain processes that 

 deform the beds of rock after they have been formed. The 

 processes of deformation cannot be observed partly because 

 of the extremely slow rate at which they operate and partly 

 because they operate below the surface where they are not 

 open to direct observation. The fact of deformation may be 

 observed, but to explain the processes by which it was effected 

 requires the formulation of a theory. This I shall call the 

 Doctrine of a Constantly Shortening Earth Radius. 



The shortening of the radius produces stresses in the 

 outer crust of the earth. This produces compression in some 

 localities and tension in others, and has resulted in greatly 

 deforming the crust. Rock beds have been bent from their 

 original position of approximate horizontality into great flex- 

 ures as well as a great many small folds and crumples of many 

 kinds. 



The most striking features of earth relief have been pro- 

 duced in this way. In fact, the reading of the geological 

 record, which is chiefly one of deposition, has been made pos- 

 sible by repeated upward and downward movements of the 

 earth's crust due to stresses. 



In localities where tension, rather than compression, has 



