Tost Glacial Geology of Ann Arbor — Wooldridge. 35 
cannot always adopt them at their first publication. Though 
the rigid processes of their science admit of little or no dispute 
yet the final results are dependent on the data and on the form 
in which those data are supplied. And in the present problem 
some of these data are so uncertain that considerable doubt must 
attach to the final outcome from the mathematical mill. And 
when as in the case now in hand the conclusions are or seem to 
be at variance with accepted and apparently solid doctrines in 
the science, the geologist may be excused for hesitating before 
he accepts the mathematical deduction. 
We will not now follow Mr. Davison into that part of his 
paper in which he treats of the elevation of mountains by the 
contraction of the cooling globe — a topic in which he is in di- 
rect opposition to Mr. Fisher — but at some future time we may 
return to the subject and state the arguments of the mathema- 
tician on this point. 
THE POST-GLACIAL GEOLOGY OF ANN ARBOR, MICH. 
BY C. W. WOOLDRIDGE. 
Many students in the University of Michigan must have 
noticed how different is the character of the ground on which 
the city of Ann Arbor is built from that of the surrounding 
country, either upland or lowland. 
The greater part of the city is built on a low hill with a 
flattened convexity of contour. The Huron river entering from 
the northwest crosses the city in a deep and picturesque valley. 
On the east side, between the city and the observatory hill, ex- 
tending from the river half a mile or more to the southward, is, 
or was, a typical Kame formation, some of the best marked 
features of which, unfortunately, have recently been destroyed 
by grading. The western part of the city is crossed by a brook 
flowing northward to the river, which is formed by the union 
of two branches, one flowing from the southwest, the other 
from the southeast. 
From the valley of this brook, the southwestern and southern 
border of the hill, on which the greater part of Ann Arbor is 
