674 



THE ICE AGE IN NORTH AMERICA. 



tery and human bones and charcoal, were found nearer the 

 surface. The total depth of the deposit was about fifteen feet. 



Fig. 185.— Argillite implement, found by H. T. Cresson, 1887, in Baltimore and Ohio RaiF- 

 road cut, one mile from Claymont, Delaware, in Columbia gravel, eight to nine feet 

 below the overlying clay bed. a, face view ; b, side view. (No. 45.72(5.) (Putnam.) 



The progress of the race from the Palaeolithic to the Neo- 

 lithic age here suggested corresponds in part to that indicated 

 by Dr. Abbott's discoveries at Trenton, where the transition 

 from the palaeolithic type of implement to the more modern 

 types, though sudden at the top of the gravel itself, is gradual 

 from the top of the gravel to the surface of the soil. For, 

 according to him,* argillite implements occur in greatest 



* " Proceedings of the American Association for the Advancement of Sci- 

 ence," vol. xxxvii. 



