1888 .] 
153 
[Wright. 
decomposed schists which characterize the locality. This is without 
question the Philadelphia Red Gravel and Brick Clay of Lewis 1 . 
The implement submitted to us was found near the bottom of 
this upper deposit, and eight feet below the surface. Not more 
than a mile from the same locality was a shelter-cave carefully 
explored by Mr. Cresson many years ago in which also palae- 
olithic implements were found in the bottom beneath large ac- 
cumulations of debris. The same railroad has cut through this 
also, and the continuity of the superficial deposit is manifest 
from one place to the other. As Mr. Cresson was on the ground 
when the implement was uncovered, and took it out with his own 
hands, there would seem to be no reasonable doubt that it was 
originally a part of the deposit, for Mr. Cresson is no novice in 
these matters, but has had unusual opportunities, both in this 
country and in the old world, to study the localities, where similar 
discoveries have heretofore been made. The absorbing question 
concerning the age of this deposit is therefore forced upon our at- 
tention as archaeologists, and to this we will direct our discussion. 
The determination of the age of these particular deposits at 
Claymont involves a discussion of the whole question of the Ice 
Age in North America, and especially that of the duality of the 
glacial epoch. At the meeting of this Society on Jan. 19, 1881, 
I discussed the age of the Trenton Gravel, in which Dr. Abbott 
has found so many palseoliths and was led also incidentally at the 
same time to discuss the relative age of what Professor Lewis called 
the Philadelphia Red Gravel. 2 I had at that time recently made re- 
peated trips to Trenton, and with Professor Lewis had been over 
considerable portions of the Delaware valley for the express pur- 
pose of determining these questions. The conclusions to which we, 
that is, Professor Lewis and myself, came were those expressed 
in the paper above referred to ; namely, that the Philadelphia Brick 
Clay and Red Gravel (which are essentially one formation) marked 
the period when the ice had its greatest extension, and when there 
was a considerable depression of the land in that vicinity ; perhaps, 
however, less than a hundred feet in the neighborhood of the mo- 
raine, though increasing towards the northwest. During this period 
of greatest ice-extension and depression, the Philadelphia Red 
T For Lewis’s Views see Abbott’s Primitive Industry, pp. 324, 335; “The Surface Geol- 
ogy of Philadelphia and Vicinity,” Proc. Acad. Nat. Sci. of Phil., Nov. 25, 1888 ; “Geology 
of Philadelphia,” Journal of Franklin Institute, June, 1883. 
2 See “Proceedings,” Vol.xxi, Jan. 19, 1881, pp. 137-145. 
