62 Report of the State Geologist. 



ingly gradual. Farther eastward they are sharply d emarcated by 

 the Helderberg escarpment, of which the western extremity may 

 be conceived as reaching to Union Springs, Cayuga county. In 

 Seneca county the change occurs by a slow and equal rise of 

 about 400 feet along li miles of nearly plain country between 

 Seneca Falls and Ovid. The first great rise occurs at Ovid vil- 

 lage, where the Portage rock forms an escarpment of 150 feet, 

 without cliffs, but sloping steeply to the north and west. 



The country may also be considered as a section of the Finger- 

 lake region (fig. 1). This name is applied to that portion of the 

 plateau which extends from Lake Conesus on the west to Lake 

 Otisco on the east, and is bounded southward by the divide 

 between the St. Lawrence and the Susquehanna watersheds. 

 The divide is marked more or less continuously by masses of 

 moraine material, filling the valleys in places to the depth of 

 many hundreds of feet, but becoming inconspicuous on higher 

 ground. The moraine, as a whole, has been considered by some 

 as corresponding to a " second glacial period." 



The region thus indicated is deeply cut by a series of ancient 

 (pre-glacial) river- valleys, roughly parallel and converging to 

 some northern point. Seaeca county lies between the deepest' of 

 these, Seneca and Cayuga lakes. It occupies the middle or 

 axial part of the Finger- lake region, which is also the lowest. 

 Its outlines appear to indicate great erosion during the Ice Age, 

 with general flattening, which has probably removed all distinc- 

 tions of relief and depression north of the outcrop of the Cor- 

 niferous limestone, though a few hills remain, greatly flattened, 

 on the south. 



The mean depth of Seneca lake valley, measured from the 

 Lodi plateau, is 1,000 feet, of which one-half is below the water 

 of the lake. 



The distinction between plateau and valley is striking when 

 one stands on high ground. From the surface of the lakes the 

 valley alone is visible ; this is especially true of Seneca lake. 



Hills. 

 The trough-like appearance of the lake- valleys of this region 

 has often been remarked. They appear destitute of side-hills; 

 or rather this feature does not come in sight except by close 

 study. 



