408 PLEISTOCENE OF INDIANA AND MICHIGAN. 



cutting of the barrier at St. Clair by some small stream, the small opening thus made being later 

 appropriated and enlarged by the great river. If the great river did not break through the bar- 

 rier at the first fall of the waters to Lake Lundy and succeeding early stages of Lake Algonquin, 

 it could not have broken through later by its own action at all, because in the later lake stages 

 the ice did not again close the northwestward connection with Lake Chicago. The lake level at 

 Port Huron did not again rise above 607 feet, because the overflow passed out partly by way of 

 Chicago and prevented any further rise of the water level at Port Huron. The distributaries at 

 St. Clair show plainly that in order to overtop the barrier the waters at Port Huron would have 

 had to rise to 630 or 635 feet altitude. But this would have been impossible with the Chicago 

 outlet open and freely connected with the waters in the Huron basin. 



Hence, although from present knowledge of the moraines it seems hard to believe that at 

 so late a stage of the ice retreat the ice was still barring the passage to Lake Chicago west of 

 Alpena and to the Lake Simcoe basin east of Owen Sound, yet the character and relations of 

 the distributaries at St. Clair seem to leave no other alternative." It is therefore concluded, 

 provisionally, that Lake Algonquin developed directly from the Lundy stage of Lake Lundy 

 and had an early stage during which its whole discharge passed southward to the Lake Erie 

 basin, the passages to Lake Chicago and the Lake Simcoe basin being still closed. 



