Geography of Ohio 387 



course across a valley, in a very short time forms a dam that may 

 divert the drainage. This has never happened in Ohio. There 

 are still other minor and infrequent natural operations that tend 

 to produce irregular drainage history. 



It is impossible to reconstruct the drainage history of Ohio 

 from the time its area was first raised from the sea. Remote 

 phases are quite beyond interpretation, and there is not complete 

 agreement among students as to the details of more recent phases. 



Under the leadership of Prof. W. M. Davis/ much progress 

 has been made in the analysis of relief features, and in the knowl- 

 edge of the processes involved. He has given the literature 

 many terms that aid in the discussion of drainage evolution. 

 When a tract in the shallow part of the sea margin is added to the 

 continent, the first streams that form across it are called con- 

 sequent, that is, the water finds inequalities in the surface, along 

 which the flow is established to the sea. The streams of Florida 

 belong to this class. 



Remote Drainage of Ohio 



Early consequent streams. When, late in the Permian pej'iod, 

 the last portion of the Ohio area rose permanently above sea 

 level, consequent drainage w^as established in the southeastern 

 part of the state. The direction of these streams, and of the 

 rivers already existing in other parts of Ohio cannot be demon- 

 strated, biit it is felt by many geologists that our area previously 

 had been a portion of a great Mediterranean sea which for a long 

 geologic time had occupied the region of the Mississippi basin; 

 and that this sea only on rare occasions was connected with the 

 Atlantic ocean across the central and northern Appalachian 

 region. If this hypothesis is correct, it is probable that the orig- 

 inal consequent streams had a southern course, to the diminish- 

 ing inland sea, and later w^re tributary to a major stream which 

 flowed southwest through eastern Kentucky and Tennessee. 

 Possibly in the northwest part of the state, along the west flank 

 of the Cincinnati arch, the original consequent streams flowed 

 westward. 



The Atlantic coastal plain drainage and the theoretical conse- 

 quent drainage of part of Ohio in post-Permian times are not 



^Geographical Essays, Boston, 1909. 



