34 THE AMERICAN NATURALIST. [Vor. XXXIV. 
The whole section for a distance of twenty feet in the com- 
paratively soft shale exhibits the sides worn very smooth, almost 
to a polish. At the point of contraction the pot-hole dips into a 
stratum of black slate which is quite highly polished. The shale 
belongs to the Hudson River Series, and the slate to the Utica 
Slate. 
The upper portion of the pot-hole was filled with shale débris 
which had evidently fallen from the cliff. This was followed by 
.. +. Shale from Cliff 
. Drift Gravel 
Hudson River Shales .... 
Slate Pebbles and Bowlders 
vus Gravel 
. Black Slaty Paste 
Utica Slates . . 
. Polished Slate Pebbles 
a stratum of five feet of gravel, similar to ordinary drift gravel, 
containing pebbles and well-rounded bowlders, varying from one 
inch to two feet in diameter. This was followed by a thick 
stratum of slate pebbles, while the lower portion of the bowl 
was filled with the black paste left from the wearing of the slate 
and containing a few perfectly rounded pebbles. There were no 
crevices to account for the carrying off of the stream of water 
which must have produced this pot-hole, and its depth indicates 
that it was formed in the bed of a powerful stream. 
At the top of the pot-hole the face of the cliff ascends sharply, 
