172
NOTES ON THE GEOLOGY OF
summer and winter, so that our brooks have the advantage, not pos-
sessed by some, of never failing, even in the driest weather. The
new waterworks at Rainsford End will obtain its water supply from
this source.
At a pit near "Chignal Hall," but situated in Roxwell parish, great
masses of conglomerate occur, some of them so large as to be
immovable by ordinary means, and so compact as to defy any effort
to break them. They have no doubt been formed by some chemical
action after the gravel was deposited, since the masses are quite
undistinguishable from the surrounding gravel in colour and compo-
sition, and it is only when struck by the pickaxe that their true
character is revealed. Several large blocks, 4 to 5 feet in diameter
and to 2 to 3 feet thick, have been removed at different times to
form rockeries, &c. After being exposed to the weather for some
years the masses become harder; a statement which equally applies
to all the gravel dug. for mending roads, but the fact is often over-
looked by those whose business it is to supply gravel for this pur-
pose. But a single year's exposure to the air greatly increases the
hardness and durability of the flint pebbles, and if this were borne in
mind our roads would perhaps be in a better state than they are now.
As far as I know, no fossils except those derived from other forma-
tions have been found in these beds, or in those next to be described,
which fact may in all probability be ascribed to the extreme cold
existing at the time of their deposition.
We now come to the principal formation of the district, viz., the
Boulder Clay. This, from its uniform appearance and from the
paucity of sections, has been little studied here by geologists, and
perhaps would hardly repay investigation except by those living in
the neighbourhood and able to avail themselves of new exposures,
such as deep drains, well-sections, gravel and clay-pits, &c. But to
one living, as I do, on the Boulder Clay, having all my capital buried
in it, and having no more interesting strata to study, many points
occur which I think will repay investigation.
The Boulder Clay, as exhibited all over the central parts of Essex,
more especially in that part known as the "Roothings," consists of
from 20 to 60 feet of stiff clay, containing worn and rounded lumps
of chalk, together with flints more or less worn, and chalk fossils of
many kinds.
At intervals, too, are imbedded boulders varying in weight from
1 lb. to 25 cwt. or more, belonging to many different formations,