742 JOURNAL OF GEOLOGY. 



to leave a surface of only moderate inequality; by no means of such 

 inequality as would gather snow fields on its higher levels, and shed 

 long glaciers down its valleys into the Piedmont seas. 



The prevailing red color of the Newark strata is also adduced by 

 Russell as indicative of a relatively warm climate, as contrasted to a 

 glacial climate. To this might be added that the slow subaerial decay, 

 from which red soils and sediments seem to be derived, is inconsistent 

 with the conditions of decay on lofty mountains, from which the 

 detritus is shed rapidly, leaving a relatively large surface of bare rocks ; 

 while it is accordant with the idea of a well denuded region, from 

 which further denudation carries material slowly. 



In examining the structural relations of the igneous rocks, it is 

 noticeable that little success has as yet attended the efforts of observers 

 southwest of the Delaware to distinguish between the intrusive and 

 extrusive origin of their trap sheets. It would seem from this that the 

 scouring of the decayed surface of the Newark belts by Pleistocene 

 glacial action has been an advantage to the geologist of to-day in New 

 Jersey, Connecticut and Massachusetts ; but an advantage that is fre- 

 quently offset by the sheets of drift which obscure or conceal so 

 many of the weaker strata in the Connecticut valley. I believe that 

 Connecticut alone has yielded a greater number of localities where the 

 contact of the sandstones on the trap sheets can be actually seen, and 

 from which good hand specimens can be secured, than all the areas 

 beyond the Hudson. It maybe noted that the map of the New York- 

 Virginia Newark area, compiled by Russell from such data as he could 

 gather together, does not give a correct impression of the crescentic trap 

 ridges of eastern Pennsylvania. I have onlv examined a small part of 

 that district, but from what was seen and from the topographic maps 

 of the Perkiomen drainage area, surveyed by the Philadelphia water 

 commissioners for a proposed new water supply, I think that an accu- 

 rate geological map of the district will disclose a more systematic 

 arrangement of forms than now appears. 1 



The deformation of the Newark areas has been a subject for much 

 discussion already, and it will doubtless furnish as much more in the 

 future. Before it can be successfully deciphered, the stratigraphic suc- 

 cession of the system must be made out ; and that has not been gener- 

 ally done, as may be seen from Russell's chapter on lithology and 



1 Since writing the above, I have seen the new geological map of Pennsylvania, 

 on which the curved trap sheets are clearly shown. 



