348 ORTMANN— THE ALLEGHENIAN DIVIDE. [April i8, 



originally drained to the westward (see Plate XII.) The primitive 

 drainage features of this region have been worked out by Davis 

 (1889), and according to him this whole region was once drained 

 by the ancient Anthracite River, running in a northwesterly direc- 

 tion through what is now the anthracite basin, its sources being 

 situated well to the east, in -the Kittatinny highland. The upper 

 part of this river was first reversed, so that it discharged southeast- 

 ward (direction of present Schuylkill), and then the Susquehanna 

 encroached upon this system, becoming finally the master stream in 

 Central Pennsylvania during Jura-Cretaceous times. The final step 

 in the development of this drainage was the capturing of the plateau 

 drainage, but also this falls largely into Pretertiary times. That 

 the Susquehanna encroached also southwestward upon the drainage 

 of the Potomac has been mentioned above, and this probably is the 

 chief change of this system which belongs to the Tertiary time. 



D. History of the Western Drainage. 



At the present time all western streams are finally united into 

 one great system, that of the Ohio, which finally runs into the Mis- 

 sisssippi and the Gulf of Mexico. In the past this was different, 

 and we know now that the present system is of comparatively young 

 age, that the Ohio is a recent stream, and that the former drainage 

 features of this region were entirely different. According to the 

 investigations of a number of writers (for instance, Foshay, 1890; 

 White, 1896; Leverett, 1902; Tight, 1903), there was no Preglacial 

 Ohio River, but in its place there was a system of northward flowing 

 streams. In the region under consideration two of them are well 

 established : the Old Monongahela in western Pennsylvania and 

 northern West Virgina, and the Old Kanazvha in West Virginia (the 

 Big Sandy belonging to the latter). How the conditions were 

 farther down is somewhat doubtful, but there might have been a 

 third river of the same general character (Licking-Miami, or Cin- 

 cinnati River, see below). 



The advancing ice of the Glacial period shut off the outlet of 

 these rivers, dammed them up, converted them into lakes, and finally 

 the waters were forced to seek another outlet, and the general slope 



