Q1 Q 



Stevenson.] '' l ^ [Aug. 15, 



freshness of the del rital covering on the bighest benches. .More than this 

 it' the time were long enough to admit of leveling the insignificanl areas by 

 ordinary erosion, it was nol too short to admit of leveling the larger areas 

 and of removing the mountains during the successive stages. Bui no such 

 leveling exists ; on the contrary the mountains and lulls still exist, and the 

 numerous benches are found on their sides. 



Had the phonomena been observed only on the west side of the Allegha- 

 nies, there might have been room for supposing thai the benches resulted 

 from the draining away of some great lake; but this hypothesis would he 

 useless, since one would have difficulty in finding a sufficient barrier at the 

 south or west for the retention of the water. For in those directions the 

 surface tails away so rapidly thai in the whole of south west Pennsylvania 

 and West, Virginia, west from the mountains, it rarely rises to even 1500 

 feet above mean tide. But there are distinct benches at 2400 feet above 

 tide. A temporary barrier, 1U00 feet high, is beyond the reach of even the 

 most indolent credulity. 



The conditions suggest that these benches were formed by ocean wear 

 between tides. Their horizontality and their excessively comminuted de- 

 posits go far toward supporting this supposition. The features closely re- 

 semble ancient sea beaches in other parts of the country. Such a supposi- 

 tion involves a submergence to a distance of more than 2500 feet above the 

 present line of mean tide ; and the submergence would have to be some- 

 what greater to account for the even crests of the Alleghanies and other 

 ridges west from the Blue Ridge. Horizontality of crest characterizes all 

 those ridges as far south, at least, as the New river of West Virginia, for 

 there they look, not like mountains as generally understood, but rather like 

 a succession of gigantic waves which have not approached near enough the 

 shore to show signs of breaking. 



To some, perhaps, the absence of marine fossils may he regarded as a 

 vital objection to this hypothesis. But not so. The detrital covering is 

 loose, not compact, and the occurrence of fossils would be cause for sur- 

 prise. Their absence is not. 



Immense deposits occur in the Rocky M axutain region which are un- 

 questionably of marine origin, yet over great areas they contain no traces 

 of fossils. The enormous red sandstone seen along the east face of the 

 Rocky Mountains in Colorado, is to all appearance devoid of fossils. Simi- 

 lar conditions exist in the sandstones of the Upper Cretaceous or Lignitic 

 series in by far the greater part of Colorado and New Mexico. They fre- 

 quently contain fucoids and remains of other plants, but animal remains 

 are absent from the loose rocks. But here and there calcareous or ferrugi- 

 nous materials have rendered the rocks compact, and in such cases animal 

 remains do occur. 



Of like character is an instance mentioned to me by Prof. Geikie. A 

 Lower Carboniferous sandstone in Scotland is celebrated a> a repository of 

 fossil trees; but though searched diligently at many localities dining a 

 whole generation, it failed to yield even a single relic of animal life until 



