THE N 1 IM S S 1 N C. C, R 1 A 1 I. A K l- S 



lake, but it marks the end of Ali;onquin, the last of the glacial 

 lakes (Iii;ure 15), and was a transition to a new lake, tor the 

 waters tell to a lower level when the ice had completely with- 

 drawn from the basin of the Cireat I akes. 



Thi: Nipissing Great Lakes 



When the ice was no longer a barrier the lakes were drawn 

 down almost to their present levels in the five separate basins. 

 The three upper lakes which occupied the Superior, Michigan, 

 and Huron-Georgian Bay basins are known as the Nipissing 

 Great Lakes. (Figure 16.) The beaches are strongest near 

 the present Lake Nipissing, in Ontario near the North Bay 

 outlet, hence the name. The col at North Bay was the low- 

 est along the Nipissing shore, so the outlet was developed 

 through it down the Mattawa River into the Ottawa — from 

 which the sea had withdrawn. By the time the Mattawa- 

 Ottawa River outlet was well established the land had risen 

 so that the sea retreated eastward to the limits of a narrow 

 estuary reaching up the St. Lawrence and Ottawa valleys to 

 a short distance west of Ottawa. The Champlain-Hudson 

 valley remained filled with marine waters. The old North 

 Bay outlet at the present time is marked by lakes and swamps, 

 with ct)nnecting dry valleys which show the marks of scour 

 of a great river. It is the route by which Marquette, Allouez, 

 Mesnard and other early Jesuit missionary explorers reached 

 Georgian Bay and Lake Superior. 



In the early stages the Nipissing lakes built beaches which 

 have been nearh' obliterated except in a small area near the 

 northeast corner of Lake Superior. The strong beach we 

 know as the Nipissing beach was made when the lake was 

 rising, its waters being spilled on its southern shores as the 

 continent continued to uptilt to the north. That the tilting 

 was rather rapid is shown b\ the "greedine«>s" with which this 

 lake bit into the old Algonquin beaches where they had been 

 cut as cliffs. In the area where the beaches are horizontal the 



69 



