The Rivers and Yalleys of Pennsylvania. 187 



waves of the real ocean. The uniformity of these mountains, 

 though debarring us of an advantage in this respect, makes some 

 amends in another. They are very regular in their courses, and 

 confine the creeks and rivers that run between ; and if we know 

 where the gaps are that let through these streams, we are not at 



a loss to lay down their most considerable inflections 



" To the northwestward of the Endless mountains is a country 

 of vast extent, and in a manner as high as the mountains them- 

 selves. To look at the abrupt termination of it, near the sea 

 level, as is the case on the west side of Hudson's river below 

 Albany, it looks as a vast high mountain ; for the Kaats Kills, 

 though of more lofty stature than any other mountains in these 

 parts of America, are but the continuation of the Plains on the 

 top, and the cliffs of them in the front they present towards 

 Kinderhook. These Upper Plains are of extraordinary rich level 

 land, and extend from the Mohocks river through the country of 

 the Confederates.* Their termination northward is at a little 

 distance from Lake Ontario ; but what it is westward is not 

 known, for those most extensive plains of Ohio are part of them." 



These several districts recognized by Evans may be summar- 

 ized as the coastal plain, of nearly horizontal Cretaceous and 

 later beds, just entering the southeastern corner of Pennsylvania ; 

 the marginal upland of contorted schists of disputed age ; the 

 South Mountain belt of ancient and much disturbed crystalline 

 rocks, commonly called Archean ; a space between these two 

 traversed by the sandstone lowland of the Newark formation ;f 

 the great Appalachian valley of crowded Cambrian limestones 

 and slates ; the i-egion of the even-crested, linear Paleozoic 

 ridges, bounded by Kittatinny or Blue mountain on the south- 

 east and by Alleghany mountain on the northwest, this being the 

 area with which we are here most concerned ; and finally the 

 Alleghany plateau, consisting of nearly horizontal Devonian and 

 Carboniferous beds and embracing all the western part of the 

 state. The whole region presents the most emphatic expression 

 not only of its structure but also of the more recent cycles of 

 development through which it has passed. Fig. 1 represents the 

 stronger ridges and larger streams of the greater part of the cen- 

 tral district : it is reproduced from the expressive Topographic 

 Map of Pennsylvania (1871) by Lesley. The Susquehanna flows 

 down the middle, receiving the West Branch from Lock Haven 



* Eeferring to the league of Indian tribes, so-called. 



t Russell lias lately recommended the revival of this term, proposed 

 many years ago by Redfield, as a non-committal name for the "New 

 red sandstones " of our Atlantic slope, commonly called Triassic. 



