39
"ON THE SUBSIDENCE AT LEXDEN, NEAR
COLCHESTER, IN 1862."
By Rev. O. FISHER, M.A., F.G.S.
Mr. Holmes has kindly sent me his paper in the last number
of the Essex Naturalist, on the subsidence at Lexden, a notice
of which was published by me in the "Geological Magazine" for
March, 1865. His explanation of the phenomenon differs from
mine. I shall feel obliged to the Editor of the Essex Naturalist
to allow me to state what I actually observed; and I think this will
be best done by giving verbatim what I wrote in my note book as I
stood on the brink of the pit, Oct. 29, 1863—the correct date of
my visit.
" May, 1861.—Occurred a subsidence in a field on the Malting Farm, Lexden.
It is on a slightly rising ground of Valley gravel, about 50 yards south of the
river, 5 or 6 feet above the surface of the river bed when full. When it fell in,
it was 20 feet to the bottom of the depression." (I must have learned this from
the farm labourer who led me to the spot. The estimate marked on my diagram
was by the eye.) "It is about 25 yards round, elliptical in form. The sides are
nearly verticil, but slightly leaning inwards at the bottom. They show the strata
undisturbed."
There is added a sketch section of the hole as I saw it.
Mr. Holmes seems to have proved that I made a mistake in
writing "1861" instead of "1862;" but it is odd that Mr. Rutley
should have repeated the error. Mr. Holmes says that the hole had
been long filled up when he visited the spot in 1884 ; and he goes
on to suggest that it may have been occasioned by a landslip. I
have seen many landslips, and I cannot connect this event with such
a cause. There was no disturbance of the surface around the hole;
it was evidently a clean-cut, cylindrical subsidence. The layers of
gravel were not broken, as they would have been if the hole had
occurred in the course of a longitudinal chasm, such as a landslip
would produce, and such a chasm would, according to the account
quoted from the "Essex Standard," have needed to have been six-
teen feet wide at this spot! Moreover, landslips on slight inclines
move slowly, but this pit suddenly appeared during the labourer's
dinner hour.
I would implore Mr. Holmes and others who are interested in
these subsidences, to visit the multitude of pits on Piddletown and
Affpiddle heaths in Dorsetshire, which I described in the "Quarterly
Journal of the Geological Society," Vol. XV., p. 187. It would form