44 



THE NAUTILDS. 



east, and in the first stage, as soon as the edge of the glacier had 

 passed the height of land north of the Mississippi and Ohio Valleys, 

 the waters were impounded, and in the southern end of the present 

 Lake Michigan and in the western ends of the present Lake Superior 

 and Lake Erie, but at a much higher level, were formed the first 

 post-glacial lakes. Lake Maumee, at that time bounded on the 

 north and east by the ice, found an outlet into the Ohio through the 

 present valley of the Maumee and the Wabash. Upon the further 

 retreat of the ice to such an extent that a way was opened for an 



FIG. 4. 



outlet towards the east, there were successively different systems 

 established. One of the earliest of these (Fig. 4) was that known as 

 the Trent outlet, which extended, as shown by the figure, from the 

 eastern end of Georgian Bay southeast across Ontario into Lake 

 Ontario. From the south side of Lake Ontario the water flowed 

 through the present Mohawk Valley into the Hudson. 



The opening of this new outlet to the east so lowered the water 

 that it was diverted from its former course through Lake Erie, and 

 the present area occupied by that lake became dry land, except for 

 such local drainage as might be necessarily incident to the region 



