Vlll 
PEEFAGE. 
another field season. Both are entitled to high praise for the skill and 
ability which they have proven by their results. 
In the summer of 1880 I revisited the district for the purpose of 
making a study of the Uinkaret, and as much of other portions as possible. 
The geological problems proposed were purely physical. With questions 
of mere stratigraphy, paleontology, or lithology, I resolved to have no 
more to do than was essential to an elucidation of the physical questions. 
The latter are remarkable, and in some respects unique. To present them 
most clearly and sharply it seemed necessary to disencumber them as much 
as possible of all subsidiary questions not absolutely essential to their 
conqjrehension. Nor did it seem at all satisfactory to gather up disjointed 
facts merely to swell the aggregate, already vast, of unreduced and uncor- 
related observations. It is not enough to know the facts; their meaning is 
of much greater concern. I have striven, therefore, to group them in their 
natural order and relations, in order that they may yield testimony as to 
the causes and processes which have made this region what it is. 
I have in many places departed from the severe ascetic style which 
has become conventional in scientific monographs. Perhaps no apology is 
called for. Under ordinaiy circumstances the ascetic discipline is necessary. 
Give the imagination an inch and it is apt to take an ell, and the funda- 
mental requirement of scientific method — accuracy of statement — is im- 
periled. But in the Grand Canon district there is no such danger. The 
stimulants which are demoralizing elsewhere are necessary here to exalt 
the mind sufficiently to comprehend the sublimity of the subjects. Their 
sublimity has in fact been hitherto underrated. Great as is the fame of 
the Grand Canon of the Colorado, the half remains to be told. 
During the summer of 1880 I was so fortunate as to have the com- 
panionship and assistance of Mr. Holmes. His reputation as a field- 
geologist is already established by his work in connection with Dr. 
Hayden’s Survey. But besides rendering valuable assistance in working 
out geological details he made many sketches which he has reproduced in 
the pictures of the text and in the panoramas of the Atlas. To praise such 
work would be superfluous. But I must call attention to a merit which 
