MORAINES OF RECESSION 461 
of forty-five miles. They were formed at the broad apex of the 
Maumee lobe expanding ona nearly level plain. In the north 
there are four parallel moraines (the twelfth to the fifteenth) 
also in a space of forty-five miles on a line running southwest 
from Rogers City past Gaylord. These moraines are banked up 
against the northeast face of the highlands and mark a great 
reéntrant angle of the ice-front. The fifteenth is 800 or goo feet 
lower than the twelfth, while the ninth near Fort Wayne (on 
a line running southwest from Paulding, Ohio) is only about 100 
feet below the sixth. At present we have no measure of the 
intervals in the north except on this steep slope. It seems plain, 
however, that if these four moraines had been laid down ona 
level plain without being banked up against the highlands the 
normal interval would have been considerably greater than it is. 
On the other hand, near Fort Wayne it seems clear that if the 
highlands of northeastern Ohio and western Pennsylvania and 
New York had been absent and a level plain there instead, so 
that the expansion could have been distributed evenly along the 
edge, the normal interval would have been somewhat less than 
it is. 
These facts seem to show that while the oscillations were 
going on, probably at a substantially regular rate, the main 
climatic amelioration and its resulting glacial retreat was also 
going on, not uniformly, but at a progressively increasing rate. 
From the first (or second) moraine near Cincinnati, where the 
great advance of this epoch had stopped and the great retreat 
begun, the ice-front retreated at first very slowly, but faster and 
faster as the front receded northward. Here again the character 
of the simple harmonic motion seems to be revealed as the 
probable manner of the varying rate of retreat. And this gives 
a decidedly astronomical quality to the cause. Whether the 
cause was due to some greater variation like precession, or to 
some slow orbital change, either of eccentricity or of magnitude 
affecting the distance of the earth from the sun independently 
of eccentricity, it may at least be said that any variation of cli- 
mate that can be so represented must spring from a cause which 
