614 GLACIAL FORMATIONS OF ERIE AND OHIO BASINS. 



TOPOGRAPHY. 



From Findlay eastward to the west fork of Rocky River this is a nearly 

 plane tract with a decided northward slant, the only prominent exceptions 

 being a small area in northwestern Lorain and eastern Erie counties, cover- 

 ing two to three townships, where occasional sandstone hills rise above the 

 general level. From Rocky River eastward it embraces a hilly district 

 with only a narrow fringe of plane country next to the beach line along its 

 north border. 



In the district lying west of Rocky River there is some vaiiety in the 

 surface contours, although no part is decidedly morainic. The district 

 between Rocky and Black rivers is exceedingly flat, and so is the narrow 

 tract east of Rocky River between the beach line and the hilly districts, 

 there being scarcely any knolls so much as 5 feet in height. From Black 

 River westward there are many low swells 3 to 5 feet, and a few 10 feet, 

 in height. They are somewhat irregularly distributed, some sections being 

 thickly dotted with them, while others carry scarcely any. The most 

 conspicuous drift features noted in this district are an esker in Hartland 

 Township, Huron County (described below), and a knoll in the southwest 

 part of the same township, which rises abruptly about 30 feet above the 

 bordering country. There is also a small district south of the Lake Shore 

 and Michigan Southern Railway, in eastern Huron County, where the 

 surface is somewhat uneven, there being valley-like depressions surround- 

 ing island-like knolls whose height is but little above that of the bordering 

 plain. The valleys widen and contract after the fashion of those included 

 among the knolls of the moraine. In the hilly districts the drift is seldom 

 aggregated in knolls, there being only an occasional knoll so much as 10 

 feet in height. 



THICKNESS OF THE DRIFT. 



The thickness of the drift, aside from buried valleys, probably averagea 

 no more than 30 feet and may possibly average but 20 feet. In the buried 

 valleys its thickness is much greater, as the rock floor of the larger valleys 

 was probably cut down below the level of Lake Erie, if we may judge 

 from data at Cleveland cited above (p. 595). Remai'kably few borings were 

 found which penetrate deeply into the old valleys. Attention has already 

 been called to a line leading from New London northeastward throusrh 



