The Rivers and Valleys of Pennsylvania. 251 



two pairs of Pocono and Pottsville outcrops at the west end of 

 the Wyoming syncline, and the three gaps where the Little 

 Schuylkill crosses the coal basin at Tamaqua ; the opposite gaps 

 in pairs at Tyrone and Bedford have already been sufficiently 

 explained. The location of the upper North Branch of the Sus- 

 quehanna is also unrelated to processes of adjustment as far as I 

 can see them, and the great area of plateau drainage that is now 

 possessed by the West Branch is certainly difficult to understand 

 as the result of conquest. The two independent gaps in Tussey's 

 mountain, maintained by the Juniata and its Frankstown branch 

 below Tyrone are curious, especially in view of the apparent 

 diversion of the branch to the main stream on the upper side of 

 Warrior's ridge (Oriskauy), just east of Tussey's mountain. 



43. Complicated history of our actual rivers. — If this theory 

 of the history of our rivers is correct, it follows that any one 

 river as it now exists is of so complicated an origin that its 

 development cannot become a matter of general study and must 

 unhappily remain only a subject for special investigation for 

 some time to come. It was my hope on beginning this essay to 

 find some teachable sequence of facts that would serve to relieve 

 the usual routine of statistical and descriptive geography, but 

 this is not the result that has been attained. The history of the 

 Susquehanna, the Juniata, or the Schuylkill, is too involved with 

 complex changes, if not enshrouded in mystery, to become intel- 

 ligible to any but advanced students ; only the simplest cases of 

 river development can be introduced into the narrow limits of 

 ordinary instruction. The single course of an ancient stream is 

 now broken into several independent parts ; witness the disjoint- 

 ing and diversion of the original Juniata, which, as I hav^e sup- 

 posed, once extended from Broad Top lake to the Catawissa basin. 

 Now the upper part of the stream, representing the early Broad 

 Top outlet, is reduced to small volume in Aughwick creek ; the 

 continuation of the stream to Lewistown is first set to one side of 

 its original axial location and is then diverted to another syncline ; 

 the beheaded portion now represented by Middle creek is diverted 

 from its course to the Catawissa basin by the Susquehanna ; 

 perhaps the Catawissa of the present day represents the reversed 

 course of the lower Juniata where it joined the Anthracite. 

 This unserviceably complicated statement is not much simplified 

 if instead of beginning with an original stream and searching out 

 its present disjointed parts, we ti-ace the composition of a single 



