The Parallel Drift-Hilh of Western Xetv Fori: .^ol 



we come to the Upper Uelderberg grou]). Like the upper mem- 

 ber of the Niagara group, the Upper Heklerberg is composed of 

 comjiact, heavj-bedded limestone, and, like the Niagara, also, 

 it forms the dividing line between much softer rocks — the Sali- 

 na below and the Hamilton shales above. The position which 

 it occupies is delineated on the map with, certainl}', an approxi- 

 mation to aceurac}'. 



Passing westward from Onondaga Valley, we find it, or should 

 find it, if not concealed by drift, presenting a continuous escarp- 

 ment as far as Cayuga Lake. West of Cayuga it reappears, and 

 continues to Seneca Lake ; and west of Seneca Lake it is con- 

 tinuous to the Genesee Eiver. "We observe, however, that the 

 line of this escarpment is not straight. It bends several miles 

 to the south when approaching Cayuga Lake, turns to the north 

 a like distance after passing Seneca Lake, and then continues 

 on a nearly straight line to the west. At its first exposure on 

 the line running north from Seneca Lake, it presents a steep 

 escarpment facing the east. 



Above the Upper Heklerberg rise the shales of the Ham- 

 ilton group, estimated by Professor Hall to be 1,000 feet thick 

 on Seneca Lake. To these succeed the Tully limestone, Gene- 

 see slate, Portage and Chemung groups, which form the great 

 mountain ridge between the Catskill Mountains and Lake Erie. 



In the Hamilton shales are excavated the greater part of the 

 rock basins occupied by Skaneateles, Otisco, Owasco, Cayuga, 

 Seneca and Canandaigua lakes. The only lake of the series, 

 Ij'ing above the horizon of the Hamilton group, is Crooked 

 Lake ; its basin is excavated in the Genesee slate and Portage 

 group. 



Having thus briefly reviewed the surface rocks of this region, 

 we Avill now consider the drift which covers them. 



As already remarked, this is arranged in parallel hills. Though 

 these hills attain their most characteristic development in the 

 region between Cayuga and Seneca lakes on the south, and Lake 

 Ontario on the north, the same peculiar arrangement of the 

 drift is noticeable eastward as far as the Oswego River, and even 

 beyond that point ; Avestward, it is not particularly noticeable 

 beyond the western boundary of Wayne County. 



The individual hills vary greatly in length, in breadth, in 



