120 
of Spirorbis limestone, all more or less rounded and mixed 
with a reddish-coloured sand. The thickness of it was 
2 feet 6 inches, and it rested on an under surface of upper 
coal measures and lower soft sandstone, which bore con- 
clusive evidence of erosion and long exposure to aqueous 
and atmospheric agencies. In the sandstone was a singular 
excavation, of a basin shape, about 2 feet deep and 2 feet 
10 inches' in diameter, and marked b' in the wood cut, filled 
with rounded pebbles and sand. One of the former was 
larger than the rest, and composed of Spirorbis limestone 
found in the neighbouring upper coal measures, and was of 
a pointed form, somewhat like the cutter of a planing 
machine, and rounded, polished, or striated on all sides but 
one. Its weight was sixteen pounds, and its form is shewn 
in the accompanying wood cut, about sVth the size of the 
original : — 
The surfaces of rocks under the drift is generally 
interesting to geologists, and is now attracting "considerable 
attention. How the hole above described was formed it is 
very difficult to say. It might have been made by an eddy 
of water carrying the stones round, and thus excavating 
the rock, but in that case we should have expected to find 
all the pebbles very nearly of a similar shape and well 
rounded, which is not the fact. The form of the stone 
herein figured, as previously stated, reminds us of a cutter, 
and if it were fixed at the bottom of a mass of ice moving 
