Lesley.] 192 [March. 



cones at the mouths of ravines, no plains of sand and clay, no deltas 

 at the embouchures of streams and heads of lakes, such as, in the 

 Auvergne, and in the Alps and Pyrenees, impress the traveller with 

 an instantaneous and irresistible conviction of slow wear and tear. On 

 the contrary, the walls of the valleys, high as they are, are vertical 

 bluffs, alternating with taluses of angular blocks fallen from them ; 

 the bottoms of the valleys are clean ; the lakes have steep shores, and 

 the plains are covered with the disintegration of their own rocks. 

 Everything one sees tells one story, and that the story of a cataclysm 

 which, at one sweep, accomplished valleys, plains, and lakes, leaving 

 next to nothing for all coming time to do, but to protect the surface 

 with vegetation, and to send an annual contribution of the meanest 

 value by the rivers to the sea. 



Two systems of valleys characterize the result, as we now study 

 it. One parallel with the coast, and produced by the sweeping away 

 of the tops of anticlinals from one to twenty miles wide and miles 

 in height; the other a transverse system of river bottoms, sunk some 

 few feet or yards below the longitudinal valley which they cross, and 

 of deep, clean, straight gaps through the bounding mountains. It 

 is demonstrable that these two systems are but two parts of one, and 

 owe their origin to the same agency, and at essentially the same 

 time. The peculiar relationship of the rivers to the gaps is sufficient 

 of itself to prove this. Not a foult has been demonstrated in any of 

 these gaps. One fault transverse to the Tussey Mountain occurs 

 near one gap, that of the Juniata, and as if, by its loneliness and ex- 

 centric position, for the express purpose of excepting to such a theory, 

 if at any time one should be presented. . It is not until the geologist 

 has passed through the whole region, and has reached its southeast- 

 ern limit, that he suspects a faulty gap. The Kittatinny or North 

 Mountain is said to be foulted at the Delaware Water Gap, and at the 

 Susquehanna; but so the Sharp Mountain was said to be faulted at 

 the Swatara Gap, until careful in.strumental work proved that the 

 coal-beds on each side of the gap were not a hair's breadth out of 

 line. A fault at the Susquehanna is evidently absent, for the very 

 outcrops of the different sandrocks can be traced, at low water, 

 from side to side. And the foult at the Delaware Water Gap is, I 

 believe, nothing but an effect of perspective upon the eye, produced 

 by the inclined lines of cliff, unsymmetrically wrought out on the 

 two sides of the gap, because the cutting force worked in a curve, 

 produced by the presence of the expiring lied Hill anticlinal on its 

 northern slope. 



