1888 .] 
143 
[Cresson, 
Philadelphia, or is replaced by schists. Just above the yellow, is 
a layer of red ferruginous gravel, in which quartzite predominates 
with a less proportion of sandstone, chert, and hornstone. These 
materials, it is true, are found in the yellow gravel, but in the red 
gravel, at Philadelphia, we have another constituent which is never 
found in the former, and that is pebbles of red shale. 
In the brick clay already referred to, lying above the red gravel, 
will be found water-worn boulders of Cambrian quartzite, Silurian 
sand-rock, and shale from the Triassic formation, for whose origin 
we must look toward the north around the head-waters of the 
Delaware. The boulder clay and red gravel are confined to cer- 
tain limits on either side of the Delaware river, and its tributary 
the Lehigh. At Philadelphia, the two deposits extend back from 
the waters of the first named stream, an average distance of three 
or four miles ; the clay deposit , in some cases, mounting the slopes 
of a line of hills in the neighborhood of the city, to a distance of 
two hundred feet. 
Without going into any further description of the postglacial 
deposits underlying Philadelphia, deposited by great floods during 
the periodical meltings of the great ice sheet, allow me to add that 
the geologist will find the same deposit running along the Delaware’s 
banks from Philadelphia to Chester, and thence southward, far be- 
yond the point in which we are interested — that of Naaman’s 
Creek. Any one who will follow the numerous deep cuts of the 
Baltimore and Ohio railroad from Philadelphia to Wilmington, will 
be impressed with the truth of these statements, and be rewarded 
with rare opportunities for study. 
In considering the remains of early man that have been found 
near the head-waters of Naaman’s Creek, it will be well to refer to 
the first discovery that attracted attention to this neighborhood 
in 1866. It is now rather late to mention it, but, although at that 
time little was thought of the remains of the rock-shelter that I 
shall describe, at the present day the implements of its several lay- 
ers are of the greatest interest to the anthropologist. We now have 
means of comparison which we did not have twenty years ago, and 
experience has taught us to preserve the smallest flake or sherd, no 
matter how uncouth it be, for each contributes its mite towards the 
history of early man. 
The remains of the Naaman’s Creek Rock -shelter luckily fell into 
hands that have preserved them, and thanks to the Museum which 
