858 : Buffalo and Chicago, or [ October, 
flat and raised only a feet feet above the water. Now Lake 
Michigan is only ten feet above Lake Erie, and the land behind 
Chicago is not more than twelve feet above Lake Michigan on 
the water-shed between it and the Mississippi basin. This low 
place on the river is therefore less than twenty-five feet above the 
water level at Black rock. It follows then that a dam of that 
height across the river at Buffalo would stop its flow and throw 
the stream over the low ridge at Chicago into the Des Plaines 
and the Mississippi. In like manner a cut sufficiently large 
through this ridge would drain off the water and leave Niagara 
dry. Chicago would then be the outlet and Buffalo would lie at 
the head of lake-navigation. Such is the delicacy of the natural 
' adjustment that has determined the relation of the two cities. 
: We may liken the lakes to a fountain-basin having two notches in 
` its rim of about the same depth. The slightest tilt may suffice 
to throw all the waste water over either of these notches and 
leave the other dry. 
_ But a dam of the size imagined would bea task of vast mag- 
nitude. This is true if regarded as a work of human engineer- 
ing. But we all know that at no distant date, geologically speak- 
ae ing, the whole region in question and much more of the northern 
=e i part of the country was covered with a sheet of ice, and that this 
= — ice moved immense quantities of earth, sand and stone from 
_ place to place, depositing them far from their previous resting 
spots. — Sometimes this great transporting agent dropped its load 
of wreckage in long lines across the country, as may be seen 1? 
~ the great terminal moraine recently traced from Long island 
Chamberlin, Upham and others. In other places these moraines 
even more, and in breadth from a few. yards to several miles. 
one of these moraine lines across the course of the pres- 
e realized. Had one of the ridges so common in 
Ohio been formed at Black rock, the Niagara river me 
by Chicago. 
nearly to the Rocky mountains by the labor of Wright, Lewis, > 
are less extensive and bulky, though equally evident. They vay 
in height from ten or twenty feet to three or four hundred feet, oF 
3 Now let us in imagination suppose that the retreating ice had i 
t] liagara river, near the place of its outflow from Lake Enge 
ped them in many other places. The possibility might 
n in North- 
ht not 
begun to flow, and the ultimate outflow of the lakes mi ae 
