GLACIAL EPOCH UPON THE EARLY HISTORY OP MANKIND. 57 
whole period between 1842 and 1905 is 5'3 feet. The Horse 
Shoe Fall has receded since Sir Charles’ visit 338 feet. There 
can be no question, therefore, that at the beginning of the 
Christian era the edge of the cataract was If miles lower down 
than now, and that at the time of the Trojan War it was at the 
head of the whirlpool rapids, nearly three miles below, and 
that at that more distant period of human history, marked by 
recent discoveries in Egypt and Babylonia, this marvellous 
cataract was just beginning its work of erosion while Canada 
was still as well within the grasp of the Glacial Epoch as 
Greenland is to-day. 
Professor N. H. Winchell’s investigations into the age of the 
Falls of St. Anthony at Minneapolis lead to almost identical 
results, results which are confirmed by the general appearance 
of almost all the waterfalls of the glaciated region of North 
America. 
2nd. There are innumerable river valleys, large and small, 
within the glaciated region whose limited depth and width 
bear indubitable testimony to the shortness of time during 
which the streams have been active in erosion. Through some 
public works in Oberlin, Ohio, I have had unusual opportunities 
the last few years to make definite observations upon the 
extent of the erosion of a small post-glacial stream and upon 
the rate of its activity. 
As soon as the glacial ice had retreated north of the water- 
shed separating the Mississippi valley from the Great Lakes, 
and up to the time when the ice had melted off from the 
Mohawk V alley, permitting the Falls of Niagara to begin their 
work, a temporary body of water occupied the Lake Erie basin 
with its outlet into the Mississippi Valley. The shore lines of 
this temporary lake are easily followed for hundreds of miles. 
Plum Creek, from which this new evidence comes, is in the 
village of Oberlin, Lorain County, Ohio, 12 miles back from 
the present lake and 5 miles back from the old shore line. 
This old shore line is 200 feet above the present lake, and 
Plum Creek is 250 feet above the lake, or 50 feet above the 
level of the shore line of the glacial lake. The creek, therefore, 
has been at work eroding its present trough ever since the ice 
retreated from the southern watershed far enough to permit 
the water of the glacial lake to settle down to the level of the 
200 foot shore line. It is well known that this level was 
determined by the elevation of the coll at Fort Wayne, Indiana, 
leading into the Mississippi Valley through the head waters of 
the Wabash Paver. Plum Creek, therefore, is as much older 
