64 NEW YORK STATE MUSEUM 



course had a uniform elevation while forming, are no longer of uni- 

 form hight above sealevel, but rise progressively toward the north- 

 east. This slow rising of the land caused a gradual canting of the 

 basins, which brought with it a relative fall of the waters along the 

 northeastern shores and a corresponding relative rise of the waters 

 along the southwestern shores. Such a progressive change event- 

 ually carried the Nipissing and Balsam lake outlets above the level 

 of the outlet at Port Huron, and the present drainage was reestab- 

 lished. As the canting affected the Erie basin as well as the others, 

 it caused a progressive elongation of that lake toward the south- 

 west, thus finally giving it its present size and shape. This same 

 canting also resulted in the farther separation of the upper lakes into 

 their present divisions. 



While this general outline of the lake history is held by many 

 geologists, others, notably Upham, combat it strongly. Mr Upham 

 holds that the elevation of the land in the northeast had progressed 

 to such an extent by the time the ice had uncovered the northern 

 outlets of Lakes Algonquin and Nipissing, that these passes had 

 been raised above the altitude of the outlet at Port Huron, and that 

 hence these passes never, or but for a brief period of time, served 

 as outlets for the waters of the upper lakes. If this is the case, 

 Niagara always carried the drainage of the upper great lakes as well 

 as Lake Erie, and its volume was approximately uniform throughout 

 its history. The strong erosion features, however, which are found 

 hi the Mattawa valley indicate that a large stream discharged here for 

 a considerable period of time; and, if such was the case, it is highly 

 probable that the present Port Huron outlet was not then utilized, 

 and that consequently the Niagara was robbed of the discharge of 

 the upper lake area. The influence on the erosion of the gorge by 

 such a withdrawal of the water must have been a pronounced one, 

 and we shall see later that certain portions of the gorge may well be 

 explained by this hypothesis. During the time of the overflow of 

 the upper waters by way of the Nipissing-Mattawa river it is not 

 improbable that, as held by Taylor and others, the sea had access 

 to the St Lawrence and Ontario basins and possibly to the basins of 

 the upper lakes. This would account for the occurrence of marine 

 types of organisms in the deeper portions of some of the present 



