RELICS OF MAN IN THE GLACIAL PERIOD. 259 



implement occurred underneath the Columbia gravel. 

 The line of demarcation is here very sharp between that 



Fig. 75.— Argillite implement, found by H. T. Cresson, 1887, in Baltimore and 

 Ohio Eailroad 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. 45,726) (Putnam). 



gravel and the decomposed strata of underlying gneiss 

 rock, which appears in our illustration as a light band in 

 the middle of the section exposed. Some large boulders 

 which could have been moved only in connection with 

 floating ice are found in the overlying deposit near by. 

 This excavation is about one mile and a half west of the 



