236 National Geographic Magazine. 



whether it was quantitatively sufficient is another matter. In the 

 absence of any means of testing its sufficiency, may the result not 

 be taken as the test ? Is not the correspondence between deduc- 

 tion and fact close enough to prove the correctness of the deduc- 

 tion ? 



33. Present outward drainage of the Anthracite basins. — The 

 Lehigh, like the Susquehanna, made an attempt to capture the 

 headwaters of adjacent streams, but failed to acquire much terri- 

 tory from the Anthracite because the Carboniferous sandstones 

 spread out between the two in a broad plateau of hai'd rocks, 

 across which the divide made little movement. The plateau area 

 that its upper branches drain is, I think, the conquest of a later 

 cycle of growth. The Delaware had little success, except as 

 against certain eastern synclinal branches of the Anthracite, for 

 the same reason. The ancestor of the Swatara of to-day made 

 little progress in extending its headwaters because its point of 

 attack was against the repeated Carboniferous sandstones in 

 the Swatara synclinal. One early stream alone found a favorable 

 opportunity for conquest, and thus grew to be the master river — 

 the Susquehanna of to-day. The head of the Anthracite was 

 carried away by this captor, and its beheaded lower portion 

 remains in our Schuylkill. The Anthracite coal basins, formerly 

 drained by the single master stream, have since been apportioned 

 to the surrounding rivers. As the Siluro-Devonian lowlands were 

 opened around the coal-basins, especially on the north and west, 

 the streams that formerly flowed into the basins were gradually 

 inverted and flowed out of them, as they still do. The extent of 

 the inversion seems to be in a general way proportionate to its 

 opportunity. The most considerable conquests were made in the 

 upper basins, where the Catawissa and Nescopec streams of to- 

 day drain many square miles of wide valleys opened on the 

 Mauch Chunk red shale between the Pocono and Pottsville. sand- 

 stone ridges ; the ancient middle waters of the Anthracite here 

 being inverted to the Susquehanna tributaries, because the 

 northern coal basins were degraded very slowly after the upper 

 Anthracite had been diverted. The Schuylkill as the modern 

 representative of the Anthracite retains only certain streams 

 south of a medial divide between Nescopec and Blue mountains. 

 The only considerable part of the old Anthracite river that still re- 

 tains a course along the axis of a synclinal trough seems to be that 

 part which follows the Wyoming basin ; none of the many other 



