96 Association of American Geologists and Naturalists. 



(B.) Causes of transportation and deposition, and on the origin of the 



materials. 



Dynamical causes of the sedimentary rocks of the globe : 



1. Earth a cooling body. 



2. Cooling bodies diminish in volume. 



3. Bodies revolving on axis if diminished in volume increase in an- 

 gular velocity. 



Application of these principles to the earth : 



Equatorial and polar currents restore the equilibrium disturbed by 

 varied angular velocity, and resulting from inertia and centrifugal force. 



Influence of the sun upon the ocean and on the atmosphere, is to aid 

 the flow of the polar and equatorial currents. 



Reasons of the circular flow of the currents of the atmosphere and 

 ocean. 



Directions of these currents in the northern and southern hemisphei'es. 



Causes of these currents permanent as the ocean and atmosphere. 



Primary ranges of this continent the same in general position inform- 

 er times as at present. 



Efiiects of these upon the directions of the great equilibrating currents 

 of the ocean over the territory of the United States before its emer- 

 gence above the level of the ocean. 



Deposition of the materials in suspension and solution in this great 

 eddy. 



Connexion of this deposite with that of the eastern British provinces, 

 and in New England, in North America. 



Evidences that even this great area of deposition of Silurian and other 

 rocks is but a limited view of the great circular flow, and of the depo- 

 sition of the sedimentary rocks of the northern hemisphere. 



Various classes of facts have led from one generalization to another, 

 until the causes of these rocks were found to require the consideration 

 of causes affecting the entire earth. 



Classes of facts mentioned as connected with such causes. 



All harmonize with the effects necessarily produced by the flow of 4 

 the polar and equatorial currents over such areas as they must have 

 flowed over in times past. 



Deduction that the materials of the sedimentary rocks of the United 

 States were transported and deposited by such currents. 



(C.) Original sources of the materials of these rocks. 

 Evidence during and subsequent to the drift epoch satisfactory. 

 Evidence preceding the drift epoch often obscure and imperfect. 



