1864.] ^"jg [Lesley. 



Silurian limestones and slates of II and III; but quartz pebbles from 

 the Middle Silurian (Llandovery) sandstone of IV, or the not much 

 more distant outcrops of the Upper Devonian and Carboniferous con- 

 glomerates of X and XII. 



The New Red is seen dipping northward against a country which 

 is lower than its own. The question is not one of a fault to produce 

 this dip : 1. Because a fault which should throw the New Red down, 

 must necessarily leave the Silurian dominating it from an elevation ; 

 2. Because the dip exists everywhere, along the estuary for 500 

 miles, where its northern coast is a mountain anticlinal of Azoic, 

 without trace of fault; 3. Because the north edge of the New Red, 

 at the place of section, is scalloped in such a form as no fault of any 

 magnitude could produce; 4. Because the exposures are good and 

 numerous, and yet there is nothing to show the existence of a fault, 

 upon the ground. 



The New Red is seen in the section dipping northward against or 

 toward a country, the surface of which is three hundred feet lower 

 than its own. There is no evidence of a wide extension of New Red 

 over that lower surface in the New Red age. On the contrary, not 

 a hillock or gravel patch of New Red is to be found throughout the 

 whole Palaeozoic country to the north or west of this, its present 

 absurdly constructed overhanging and outdipping margin. How is 

 this to be accounted for? 



There must have been some barrier to the New Red waters be- 

 tween the Schuylkill and the Susquehanna, to correspond with the 

 barrier which we see everywhere else between the Hudson and the 

 James. Otherwise the New Red waters would have overflowed, by 

 at least three hundred feet, the Silurian Valley in its rear, and pene- 

 trated to valleys still further back by means of the principal gaps in 

 the Kittatinny Mountains through which the Schuylkill, the Swatara, 

 and the Susquehanna rivers flow. What was this barrier ? 



I think none can be suggested but one composed of the originally 

 much more elevated surface of the Silurian Valley itself. Carry up 

 the whole mean level of the Palaeozoic area — the valley beds up to 

 the present height of the mountains, and the mountain crests to a 

 proportionately greater altitude, the gaps to correspond with both, 

 and the anticlinal and synclinal structure to determine the face of 

 the surface at any given stage of the process, — and we have the re- 

 quired barrier to the estuary of the New Red; the explanation of its 

 top Conglomerate ; a good reason why there are no New Red traces 



