Tertiary history of the Grand Canon District, with atlas

This work is chiefly devoted to a description of the methods and results of EROSION upon a grand scale. Since erosion depends for its efficiency principally upon the progressive elevation of a region, and upon its climatal conditions, these collateral subjects are also discussed in their relations to the principal theme. And in general such an erosion influences and is in turn influenced by the whole train of phenomena of which physical geology takes account. I have endeavored to show in what manner and to what extent the most important of these events and groups of events are correlated. In the analysis and synthesis of these processes may be found the materials for reconstructing the history of the evolution of the physical features of the region. This history is indeed but an outline, but in it appear many things which would not readily be discerned without such a comparison.