460 FRANK BURSLEY TAYLOR 
and extending over into Ohio. At the sixth and fifth moraines 
the ice-front began to push slightly forward down the Miami 
valley, but the lobe did not become distinct until the fourth 
moraine. From that to the first moraine the Miami lobe devel- 
oped more and more individuality. The first four moraines mark 
the fully developed lobe and the circumstances under which they 
were made probably accounts for the smallness of two of their 
intervals —eight and twelve miles between the second and third 
and the third and fourth respectively. The Miami was the 
smallest and narrowest of the four valleys and hence its ice-lobe 
was more cramped than the others. Besides, there was no such 
concentration of advance in the Miami valley as there had been 
before in the Maumee. The pressure was relieved by the other 
three lobes, while from Detroit and Cleveland to Fort Wayne 
the large Erie-Huron lobe was cramped by highlands on its sides 
and hence pushed forward in a comparatively long, sharp point. 
In this discussion of the intervals we have followed the ice in 
its advancing phase. We have only to reverse the order of 
events to see that the influence of topography was substantially 
the same during the retreat. 
This, as it seems to me, is the true explanation of the varia- 
tions of the intermorainic interval, and it indicates that the nar- 
row intervals which prevail from the first to the ninth moraines 
are not out of harmony with the wider intervals from the ninth 
to the thirteenth. The shorter intervals of these moraines do 
not indicate, as might be supposed, a radical difference in cli- 
matic conditions, nor of amplitude of oscillation, nor, possibly, 
of the rate of the general retreat, but mainly the influence of 
topography. 
If the moraines showed nothing further it would seem clear 
that the rate of the main retreat had been perfectly uniform, or 
at least very nearly so. But if we turn to northern Michigan 
and compare the intervals of four moraines there with the four 
south of Fort Wayne, an increase of the interval northward 
seems to be suggested. South and southwest of Fort Wayne 
four parallel moraines (the sixth to the ninth) lie within a space 
