Geography of Ohio '• 395 



cut in the Erie and Ohio shales. Some of the smaller tributaries 

 of the Black river in Lorain county exhibit the directive influence 

 of the lake ridges. 



Vermilion river. This is also a short stream. It rises in Ash- 

 land county, and because of a difference in rock structure has a 

 flatter cross-section in the Huron county part of its course than 

 has the Rock}^ river; but in the northern part of Huron county 

 it cuts through the outcropping Berea sandstone into the underly- 

 ing shales; this part of its course is a rock channel, in some places 

 very beautiful. In the last two miles of its course the river is 

 sluggish. 



Huron river. The sources of this stream are in Seneca and 

 Huron counties. It has a general northward course, passing 

 Monroe ville and entering the lake at Huron. South of the cen- 

 tral part of Huron county its channel is cut in the Berea sand- 

 stone, locally forming beautiful scenery. Ncaring Monroevill the 

 underlying shale outcrops, and the stream has cut deeply into 

 this easily eroded horizon; at Milan the channel shows fifty feet 

 of shale bank. These cliffs gradually die out, and through the 

 last four miles of its course the river has a wide valley and is very 

 sluggish. Along the Huron, in the vicinity of Monroeville, the 

 shales contain numerous large concretions; many have fallen 

 from the banks and are so large that the stream does not at once 

 carry them away. 



Sandusky river. Of the rivers so far discussed, this has the 

 largest drainage basin. Its numerous headwater streams start 

 in Richmond, Marion and Hardin counties. Some of the trib- 

 utaries flow to the southwest before joining the major branches. 

 This direction of flow reflects the influence of moraine ridges on 

 drainage; the glacial map of the state shows how the moraines in 

 this part trend south of west. The Sandusky cuts into limestone 

 throughout nearly all of its course; only at a few places does shale 

 appear in the channel; the last few miles of its course, before 

 emptying into the Sandusky bay, are in the area of the Monroe 

 formation. 



Portage river. This short river rises in Hancock county. Its 

 basin includes nearly half of Wood county, a small portion of San- 

 dusky county and some of Ottawa. The Portage has not cut a 

 channel of much importance anywhere in its course; the rocks 

 disclosed by it are limestone. 



