WITH A LIST OF THE MOLLUSCA OCCURRING THEREIN. 3
is 40 feet deep.4 Boynton Hall stands on the same side of the brook
as the deposit, though at a distance of about three-quarters of a mile
Fig. 1. Ground Plan. A and B, outlets ; C and D, rabbit holes: E, spot where Cochliocopa.
tridens and Cyclostoma elegans were principally found.
N.W., and about 100 feet higher. It is said, however, that our well
at "Stevens" was not affected. Our house stands about 300 yards
from the deposit, but on the opposite side of the brook, and about
100 yards from it, at very nearly the same elevation. Chignal Hall
stands beyond our house on the same side of the brook, and about
the same distance from it, though rather higher; but here, it is
said, the well was lowered 4 or 5 feet.
The Cann Valley has been excavated out of the Boulder Clay,
and the Glacial gravels which overlie, and almost everywhere
conceal, the London Clay, throughout the district. The junction of
the Middle Glacial Beds with the Upper, or Chalky Boulder Clay, is
well seen in a gravel pit at Writtle, two miles to the S., figured in
Woodward's "Geology of England and Wales" (p. 314). Here the
transition is very sudden—" two or three inches taking one from
sands and gravels to the chalky clay, the latter resting on upturned
edges of false-bedding in the former, and receiving a reddish tinge
from the contained iron," as Mr. Clark remarks in the paper above
mentioned. Glacial gravels are abundant in the valley, and are freely
4 Boynton Hall well draws its supply, not from the gravels which outcrop in the bottom of
the valley, but from a thick seam of gravel in the Boulder Clay. Its being affected by the drain-
ing of the alluvium is very remarkable.—W. H. Dalton.
B 2