J. W. Powell's Survey of the Rocky Mountain Region. 853 
district in plaster, exhibiting the forms due to upheaval as they 
would appear if unmodified by degradation. He prepared also 
a topographic model, exhibiting the same forms as actually 
modified; and the two models will be reproduced by photo- 
graphy to illustrate the report.. The treatment of the second 
element of structure is of a thorough character and includes a 
discussion of the general principles which control the sculpture 
of the land surfaces of the earth by rains and rivers. The vol- 
ume is ready for the binder. 
Geological work by Captain Dution—Captain Dutton resumed 
his exploration of the same field which he has been studying 
for three years, having recognized in it a certain unity which 
renders it eminently adapted to an important monograph. The 
region explored by him is centrally situated in the territory of 
Utah, extending from Nebo in the Wasatch nearly southward 
a distance of about 180 miles and having a maximum breadth 
of about 60 miles. It possesses certain features which serve to 
distinguish it both topographically and geologically, and he 
roposes to call it the District of the High Plateaus of Utah. 
It consists of a group of uplifts now standing at altitudes be- 
tween 9,000 and 11,500 feet above sea-level, while the general 
platform of the country is from 5,000 to 7,000 feet high. The 
plateaus have been carved out of this platform by great faults, 
and the general structure corresponds closely to that escribed 
by Professor Powell under the name of the Kaibab structure 
and illustrated by*him in his section of the region travers 
the Grand Caiion of the Colorado. The relations of this belt 
of high plateaus to the regions adjoining are of special interest. 
At the close of the Cretaceous, the country lying to the east- 
ward of it by gradation from an oceanic to a lacustrine 
condition, the intermediate stage presenting doubtless a strict 
analogy to the condition of the Baltic. This Kocene lake area 
Colorado River. During Cretaceous and Eocene time the area 
now occupied by the Great Basin was dry land, and its dennda- 
tion must have furnished a large part of the sediments which 
were spread over the bottom of the great lake. The movements, 
which took place during the Eocene, at last resulted in the 
desiccation of the lake, and though a strict chronological correla- 
tion to European and other divisions of time cannot be made 
with certainty, it may be provisionally inferred that this desicca- 
tion was completed before the commencement of the Miocene. 
It was brought about by the more rapid uplifting of the lake 
area than that of the Great Basin until at last the former area 
became the loftier of the two, thus reversing their relative alti- 
tudes. The lake area is now a portion of the so-called Plateau 
Country and since the commencement of the Miocene (para-Mio- 
