296 PROCEEDINGS OF THE ACADEMY OF [1880. 



THE TRENTON GRAVEL AND ITS RELATION TO THE ANTIQUITY OF MAN. 



BY HENRY GARVIIiL LEWIS. 



In the course of an investigation of tlie Surface Geology of 

 Southeastern Pennsylvania, some facts have been developed in 

 connection with one of the gravels, which,, bearing directly upon 

 the Antiquity of Man in America, become of great interest.. 

 Among the many scientific problems now attracting attention^ 

 none perhaps holds a more prominent position than that of the 

 Antiquity of Man. It is a subject which, notwithstanding the 

 numerous facts gathered and the bulk of literature published, must 

 be regarded as still in an undecided condition. 



As the Delaware is in many respects a tj'^pical river, and as 

 therefore deductions made here will hold good for the valle3^s of 

 many other rivers of the Atlantic coast, it is thought that a record 

 of the investigation will be of more than mere local interest. The 

 subject will be approached from a purely geological standpoint. 

 The main difficult}^ in inquiries of this kind has been the absence 

 of exact geological data. Hasty conclusions have been drawn 

 from an inspection of relics found in a gravel, which a more 

 accurate knowledge of the age of that gravel would not have 

 sustained. 



The writer has shown in former papers ' that the gravels of the. 

 Delaware Valley belong to several distinct ages ; and if therefore 

 at any place the remains of man are shown to occur, it will be all 

 important to know to which of these gravels they should be 

 referred. 



The surface formations of Southeastern Pennsylvania may be 

 divided into five clays and four gravels. The following is believed 

 to be the succession in which the^- occur, beginning at the 

 oldest: (1) Jurasso-Cretaceous plastic clay; (2) Tertiary clays, 

 (" Brandon Period ") ; (3) Bryn Mawr gravel, (upper Tertiary); (4) 

 Branchtown clay; (5) Glassboro gravel, (Pliocene); (6) Phila- 

 delphia red gravel, (Champlain) ; (7) Philadelpiiia brick-clay, 

 (Champlain) ; (8) Trenton gravel, ("Eskimo period"; ; (9) Recent 

 alluvium. Of clays, the oldest is the Jurasso-Cretaceous plastic 

 clay exposed at Turkey Hill, Bucks Co. A similar plastic clay, 



1 "The Surface Geology of Phila. and vicinity." Proc. Min. and Geol. 

 Section, Acad. Nat. Sc. Phila., Nov. 1878. 



