THE TERTIARY HISTORY OF THE GRAND CANON 
DISTRICT. 
BT CLARENCE E. DUTTON. 
ABSTRACT OF THE MONOGRAPH. 
This work is chiefly devoted to a description of the methods and 
results of eeosion upon a grand scale. Since erosion depends for its effi- 
ciency 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 physi- 
cal geology takes account. I have endeavored to show in what manner 
and to what extent the most important of these events and groujjs 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. 
Chapter I gives a brief and summary account of the geography of 
the Grand Canon district and of the distribution both of its topographical 
and of its principal geological featui’es. It is situated chiefly in north- 
westeim Arizona, with an extension northward into Utah. Its length 
from northwest to southeast may be taken arbitrarily at about 180 miles, 
and its width from northeast to southwest at about 125 miles. As no nat- 
ural boundary can be fixed for its southern portion, its area may be placed 
