158 PROCEEDINGS OF THE ACADEMY OF 



and the Cretaceous at Maidstone, England. The Hadrosaurus clays, belonging 

 to the upper Cretaceous, as indicated by the presence of many molluscs of the 

 Ripley Group of Mississippi, appear indeed to be separated from the clays in 

 question by a great lapse of time. The age is therefore probably truly Wealden 

 or Neocomian. 



These facts indicate the existence of a barrier to the eastward of their present 

 position, which for a long period prevented the access of salt water. This 

 barrier was no doubt an anticlinal of the Appallachian series, outside of that 

 which walled in the Triassic fresh-water area, and, like it, parallel with the 

 general series of anticlinals of the present Allegheny range. That it was, like 

 the latter, at one time submarine, and, gradually rising, finally enclosed the 

 area in question, the waters of which soon became fresh, from the numerous 

 rivers which flowed into it. 



On the gradual elevation of this fresh-water valley, with its included beds 

 of clays, etc., the Delaware river cut its way through the latter nearly to the 

 south-eastern rise, and was then deflected along the base of these first eleva- 

 tions of the bounding anticlinal, in a south-west direction. Thus is accounted 

 for the apparently singular phenomenon of the great bend of the Delaware 

 River, near Bordentown. For after penetrating the high ranges of the Blue 

 Mountains, it remains to be turned, apparently, in a level country of sands 

 and clays. 



We must suppose the coast line to have been not far from the south-eastern 

 base of this anticlinal, and that a subsequent submergence brought the marine 

 deposits near to the margin of the fresh, and gave the latter the south-east dip 

 visible at the section at. the Pea Shore. I have not yet been able to ascertain 

 the relative position of the margins of these beds, nor the nature of those that 

 conceal the supposed anticlinal. A system of borings at a distance of two or 

 three miles from and parallel to the Delaware, would do much towards ex- 

 plaining this point. It is to be hoped that this may be undertaken by the 

 present State Survey, under Prof. Cook. 



At the present time, the cities of Alexandria, Washington, and Baltimore 

 stand upon its deposits, and Philadelphia is probably underlaid by its margin, 

 as well as the adjoining margin of the Gneiss. Indeed, the location of the 

 prominent cities of the Atlantic States appears to have been determined by the 

 fine sites and water-powers offered by the junction of the high rolling country 

 of the Gneiss formation, and the lower and more level regions of the supposed 

 Neocomian, Cretaceous and Tertiary. Where the Gneiss strikes the ocean, is 

 situated our greatest seaport. New York. Trenton, Philadelphia, Wilming- 

 ton, Baltimore, Washington, Alexandria, Richmond, Raleigh, Columbia, and 

 Milledgeville, Georgia, are all on this line of junction. The elevated Gneiss 

 hills furnish healthy and beautiful residences, the fall furnishes water-power, 

 and the lower level, water communication, and a light soil most suitable for 

 gardening and the production of provisions for these centres of population. 



The succession of strata is rather more complete in New Jersey than has 

 been generally supposed. At the basis of the series occurs the present fresh- 

 water period. Then the marine Hadrosaurus or Ripley clays, and lower Green- 

 sand bed. This deposit my friend John Smock, first assistant of the State 

 Survey of New Jersey, informed me had not found to contain Chelonians. On 

 examination of my own collections and explorations, and those of the Academy, 

 I find this to be true up to the present time. The Chelonians, then, have so 

 far been found in the middle bed of green sand only. Third, the sands, greea 

 sand, and limestone pertaining to the middle bed. Lastly, the upper green 

 sand bed, which appeared to approximate closely the London clay, or lower 

 Eocene, in the character of its fauna, in its molluscs, according to Conrad, and 

 especially in the genus of serpents, Palaeophis of Owen. 



[June, 



