BUFFALO SOCIETY OF NATURAE SCIENCES 83 



and is cut through Portage shales to a point four miles west of 

 Hamburg where it joins the new, narrow channel of the east 

 branch which begins above Hamburg. 



Buffalo creek and Cazenovia creek seem to have continued 

 their course practically in their ancient valleys. These had been 

 dammed by the glacier and long finger lakes had formed in the 

 upper courses. These had drained in various ways but after the 

 melting away of the glacier the streams resumed their old 

 courses. 



The great lakes which characterized the topography of Erie 

 county during the recession of the ice sheet disappeared when 

 the tremendous supply of water derived from the melting ice 

 ceased. Our present Lake Erie is their shallow successor. It 

 occupies an ancient preglacial depression. It is held as a lake 

 only by the ledges of Onondaga limestone and Niagara limestone 

 which form the lowest point in its rim. This lake may persist 

 until the Niagara river has worn back its canon to a point where 

 the Onondaga limestone dips beneath the lake bottom. At the 

 present rate of tilting at the north this may never happen. The 

 future of Lake Erie depends upon the relation in time between 

 the rate of erosion of Niagara river and the rising of the 

 Onondaga limestone across it by this uplifting process. This 

 is further complicated by the result of this tilting upon the 

 upper Great Lakes. These supply the water which is the main 

 erosive agent of Niagara river. A continued tilting of the 

 northern ends of the upper lakes must result in the abandonment 

 of the Detroit river as an outlet and the resumption of the glacial 

 channel across the low lying divide at Chicago. The abandon- 

 ment of Detroit river will cut off the main water supply of Lake 

 Erie and so reduce the erosive force of its outlet as to lengthen 

 its life indefinitely. 



The Fossil Content of the Rock Formations of Erie County. 



Although the fossils of a few of the formations of Erie 

 county have been subjected to detailed study by several observers 

 many have received practically no attention from palaeontologists 

 and there is a great opportunity for special students along this 

 line. 



