Cresson.] 
146 
[Dec. 19, 
marks the innermost edge of the outcrop overhanging the hollow 
P Y 6r, a perpendicular line dropped to the intersection of the 
ground line 1 , would measure five and one-eighth feet, the height of 
the projection of the rock above the ground before the excavations 
were commenced. 
Twenty-two feet, eight inches, from the outcrop i£, measured from 
its inner face P, there is still another outcrop of Laurentian rock, 
marked G on the diagram. This marks the opposite side of the 
hollow, the profile outline of which is easily made out by the thick 
line running from G to Y. Carrying the eye upward to P, the an- 
gle of projection of the rock, over the depression P Y 6r, is readily 
understood. 
It is thus evident how admirably the place was adapted to the 
wants of the early hunters of the Delaware Valley, whether it be as 
a shelter, or as a place of defence against their enemies. 
Contenting ourselves with this hasty sketch of the shelter’s pro- 
file, and the suggestion that the hollow beneath the projecting 
rock was the result of erosion, let us consider for a moment the 
layers of earth, sand and gravel that filled it, these being inter- 
mingled with rude implements, broken bones, and charcoal, indi- 
cating that man at times had resorted to the spot. 
Layer C . — This was composed of schist, resting on the Lauren- 
tian ? bed rock ( T ) of the shelter. A layer of aqueous gravel of 
the same character as that underlying Philadelphia rested on the de- 
composed schist. The greatest depth of the red gravel layer was 
4 feet inches, measured from the layer of decomposed schist. 
Least depth of gravel observed, 1 foot, 3 inches. These measure- 
ments were verified by me at the final excavations made through 
the shelter by the Baltimore and Ohio railroad company in 1887. 
New geological specimens were also obtained of the different lay- 
ers, as some of those obtained in 1866 were lost during changes 
that have taken place in the household of the gentleman who pre- 
served the collection until the time of its presentation to the Pea- 
body Museum. 2 
Layer A . — This was a layer of grayish white brick-clay mixed 
with yellow clay similar to that underlying Philadelphia, on top of 
1 The point where the line P cuts the ground line G is here referred to. 
3 A portion of the specimens from the rock-shelter were accepted in 1884 as a consid- 
eration for my services rendered in superintending the excavations during the summers 
of 1866-7-8. At the earnest request of the curator they have been presented to the Pea- 
body Museum. 
