66
NOTES—ORIGINAL AND SELECTED.
End, visited during our excursion to Writtle. There are also some
fine pits in it near the water-tower south of the town.
These constituents of the Glacial Drift hereabouts, the Sand and
Gravel Beds and the Boulder Clay, vary very considerably in thick-
ness. We may also discover that in one place Boulder Clay lies
directly on London Clay, while in another the Sand and Gravel has
but a few small patches of Boulder Clay resting upon it. But a
glance at the map of the Geological Survey shows the close associa-
tion of the two formations, and makes it evident that they both
belong to the same geological period, though there may be nothing
in any sections to stamp the Sand and Gravel series as Glacial, in
the sense in which the Boulder Clay is rightly so termed. As
regards the variations in thickness of these constituents of the
Glacial Drift, I learn from the Geological Survey Memoir, on Sheet
47, that "in wells at Scravels, near Broomfield, there are 12 feet of
gravel, and at Broomfield School 18 feet, covered respectively by 3
and 7 feet of Boulder Clay." And near Great Waltham Church the
gravel is more than 24 feet thick; at Great Leigh's Parsonage, 20
feet; and 5 furlongs east of it, 30 feet of gravel were found under a
like thickness of Boulder Clay. At Troys Hall, Fairsted, there were
60 feet of Boulder Clay above but 11/2 foot of gravel.
Formerly the Chalky Boulder Clay was much used for marling
the land, and the old marl pits continue to furnish sections, though
they have become disused as sources of manure. Inspection of
some of them will show how much the uppermost two or three
feet have been deprived of the Chalk they once contained through
the action of the weather. The depth to which the Chalk has been
dissolved away is variable, as it depends on the greater or less per-
meability of the Boulder Clay at any given spot.
NOTES—ORIGINAL AND SELECTED.
Capture of Otters near Chelmsford.—"The Essex County Chronicle'' of
May 12th, records that on "Monday afternoon, May 8th, a man named Abbott,
in the employment of Mr. G. B. Ling, caught a young otter in the head-water at
Springfield Mill, Chelmsford. The animal, which is about three months old, is
being kept alive. The same afternoon, also, some pupils at the Arc Works
caught a small otter in the river at Chelmsford."
Uncommon Birds near Birchanger.—Mr. A. P. Church, in a letter
recently received, says : "It may interest you to know that we have a pair of
Green Woodpeckers breeding within a very few yards of our house at