THE ESSEX FIELD CLUB.
267
Mr. W. Cole's absence.—The President alluded to the absence of the
Hon. Secretary, owing to illness. He believed that this was the first time that
Mr. W. Cole had missed an Ordinary Meeting since the foundation of the Club
in January, 1880.
Ennomos autumnaria in Essex.—The Assistant Secretary, Mr. B. G.
Cole, exhibited a specimen of a rare British moth, Ennomos autumnaria
(alniaria), presented by Mr. Whittle, being one of three specimens taken at
light at Southend, The moth had certainly not occurred many times in Essex.
Pied Blackbird.—Mr. A. F. Hogg, M.A., Principal of the Institute,
exhibited a mounted skin of a Pied Blackbird. The bird had been kept in
confinement for five years. After the first and second moults the plumage was
quite normal, but at the third moult it became pied, and the white marks were
quite symmetrical.
Mr. J. M. Wood said that he had known several specimens of pied blackbirds,
but not one was symmetrical in the white markings.
Mr. Miller Christy also made some remarks on the specimen, which he
thought of much interest, as tending to throw light on the causes of albinism,
partial or complete, in birds. It was, he thought, of interest from two special
points of view. First, there was the fact that the bird was pied absolutely
symmetrically on both sides. Secondly, there was the fact that it was not pied
from birth, but became so (through some unknown cause) on its third moult.
The change might possibly be accounted for by some peculiarity in the food on
which it was fed ; but it was hard to account, on this supposition, for its having
become pied symmetrically on each side. Mr. Christy added that he could
recall no similar recorded instance.
Remarks upon Quartzite Pebbles from Cheshunt.—Mr. John French
exhibited three quartzite pebbles, and remarked on them as follows :—
These pebbles were obtained from Lea-valley gravels at Theobalds Park,
Cheshunt, at an elevation of perhaps 50 to 60 feet above the present stream.
The enquiry is, whence they came and how they reached that place.
Going back about a century, we find that Professor Buckland traced the
origin of similar quartzites to an immense bed of Triassic age in which they occur
in their rounded and polished state. This bed is exposed near the towns of
Birmingham, Stafford, and Bridgworth. He found that the pebbles had been
carried down the ancient Midland valleys of the Evenlode and the Cherwell, and
at Oxford they occurred in immense quantities. Proceeding along the Thames,
they were distributed in diminishing quantities until Essex was reached. But
inasmuch as these are also distributed almost all over Essex and Herts, and even
into Suffolk, that explanation of Buckland's was insufficient.
Many years afterwards Professor Prestwich took up the subject and found
there was evidence of a southern drift, and he attributed the origin of these
quartzites, in common with other components of the gravel, to a drift originating
in France and travelling over the Wealden anticline in a northerly direction ; he
traced it as far as Westleton, in Suffolk ; and as the gravel occurred there in
great and characteristic quantities, he gave it the name of the Westleton-bed. This
bed he traced from that place not only in a southerly direction, but south-
westward as far as Heading or thereabouts.
Quite recently Dr. Salter has taken up the subject and gone very minutely
into detail. He found that what evidence remained of a southern drift was quite