324 The American Geologist. November, 1897 
the part of the author and will be of advantage to the student who is 
already somewhat acquainted with the elements of geology. But the 
reviewer questions the advisability of presenting so much df^tail to the 
student who is totally unfamiliar with elementary geology, and who has 
only a brief period, possibly one or two terms, to devote to this subject. 
But at the same time to the teacher who must present the subject thus 
briefly and to the som^jwhat advanced student this character of the syl- 
labus will appeal favorably. u. s. g 
The Glacial Lake Agassiz. By Wakren Upham. Monograph xxv, 
U. S. Geological Survey: 4°, xxiv, 658 pp. 38 pis. Washington, 1896. 
Geologists on both continents have awaited for some time the appear- 
ance of this elaborate monograph on the great glacial lake which once 
occupied central North America, whose features had been partially 
described in previous papers by Mr. U^jham aud touched upon by 
other observers. The several years devoted by Mr. Upham to the field 
work and elaboration of results bear excellent fruit in the carefully di- 
gested and admirably arranged discussion found in this volume which 
made its a^jpearance a few months ago. The work so well begun under 
the Minnesota Survey has been greatly increased in value by the ex- 
tension afforded by the United States and Canadian Surveys. 
After a general introduction outlining the lake area and early ob- 
servations, together with methods of study pursued by the author, the 
reader is made acquainted with the physical features of the area 
covered by the lake and of neighboring districts. The geologic forma- 
tions underlying the drift are then discussed and their relationship to 
the physical features briefly touched upon. These formations are dis- 
cussed both in the light of surface outcrops and of deep well records. 
The author concludes that the greater part of the area of lake Agassiz 
was once covered by Cretaceous dexx)sits and that the main physical 
features have been produced in post-Cretaceous time by processes of 
denudation following a widespread or epeirogenic uplift. A broad 
plain or base leveled region was formed far below the uplifted Cre- 
taceous surface, whose reduction to base level is thought to have occu- 
pied not only the Eocene and Miocene periods but also most of the 
Pliocene. This base leveled region, stretching from the Rocky mount- 
ains eastward to the Archaean hills on the east border of lake Agassiz, 
and northwestward x^fist Hudson bay is thought to have been drained 
in Tertiary time into the Atlantic between Labrador and the southern 
point of Greenland. An uplift of this base leveled region followed in 
the late Pliocene, during which the trough of lake Agassiz is supposed 
to have been formed. The depression of Hudson bay beneath the sea 
is referred to the time of culmination and departure of the great ice 
sheet. The course of the pre-Glacial rivers flowing from the Creta- 
ceous area west of lake Agassiz after the late Pliocene uplift, was 
probably northeastward across the Hudson bay basin. The present 
channel of the Missouri riverj as shown by general Warren and profes- 
sor Todd, dates only from the Glacial period. The pre-Glacial drain- 
age of the upper Missouri watershed may have occupied the James 
