290 GEOLOGY OF OHIO. 



Each of these narrow terraces is represented in Huron county by broad 

 expanses of level land, showing that they are old water plains, diversi- 

 fied by sand dunes and remains of old lake beaches, and by the various 

 channels excavated by the present streams. In the eastern and south- 

 ern parts of the county the surface rises to a level, geologically and topo- 

 graphically, above the summit at Berlin Heights, and is marked by irreg- 

 gular undulating hills of the clay Drift. , 



The topography is also modified by the valleys of the Vermillion and 

 Huron rivers and their tributaries ; the valleys showing old flood plains, 

 in places from one-half to three-fourths of a mile wide, with blufls from 

 fifty to sixty feet in height. Vermillion Kiver has its source in Savan- 

 hah Lake, Ashland county, where it connects with streams which are 

 tributary to the Ohio ; the valleys uniting at the divide in a continuous 

 channel, now deeply filled with Drift, indicating that the drainage of 

 both valleys was formerly southward. The connection of the head- waters 

 of Huron River with the streams running south is not so distinctly 

 marked, yet it can easily be traced between them and two valleys, one to 

 the east and one to the west of Mansfield, in Richland county, where the 

 drainage is also to the south. This is indeed a general characteristic of 

 the streams in this part of the State, which have their origin near the 

 divide, between the waters of the Lake and the Ohio River. They are 

 not separated by a water-shed, and fed by springs flowing from opposite 

 sides of it, but take their common origin in valleys having a northerly 

 and southerly direction, and usually commence in marshes or small 

 lakes, now occupying the summit of the pass. Here they receive the 

 surface drainage from the higher lands on each side, which accumulates 

 in the pond or marsh, and gives rise to streams flowing in opposite direc- 

 tions. The valleys of these streams are filled with alluvium, resting 

 upon Drift deposits ; and they have rocky beds only in places where ob- 

 structions have diverted the stream into new channels. 



SURFACE DEPOSITS. 



The surface deposits of Huron county afford a good illustration of the 

 influence of recent geological changes in preparing a soil fitted for the 

 work of the agriculturist. The underlying rocks are sandstone, argilla- 

 ceous and bituminous shales, with a strip of lime rock in the north- 

 western border of the county. The disintegration of these rocks in place 

 would have formed a narrow belt of calcareous soil on the western mar- 

 gin, next a broad, irrregular surface of tenacious clay, and over the rest 

 of the county a soil of comparatively barren sand. These rocks have 

 been broken up and pulverized by Nature's vast ice-plow; the finely 



