FROM MALDON TO CHELMSFORD, AUGUST 8th, 1891. 201
of any important fault which points in this direction. The only one,
indeed, shown on the Geological Map which may possibly continue
to exist in this locality is that which throws down the Chalk on its
northern side to a depth of about 40 yards at the Royal Naval
College, Greenwich. But even in the case of faults of much greater
size, it is in the highest degree rash to prolong them in any direction
without evidence of their existence. To illustrate this point I have
brought with me a map of a portion of the Yorkshire Coalfield, which
gives a fair notion of the average state of things there. It becomes
at once evident on glancing at this Yorkshire map that where faults
exist others range more or less parallel with them, and are crossed
by a second series having an average direction nearly at right angles
to that of the first-named group. The evidence afforded by a map
like this is of special value on account of the absence of drift, the
greater facility of tracing faults at the. surface (as compared with
Essex), owing to the interstratification of hard and soft beds, and to
the information obtainable from colliery plans. Yet it shows how
few faults preserve an independent existence for a distance of even
six or seven miles, most of them being stopped off by others crossing
them in a much shorter distance. And—to return to Essex—we
have no evidence of the continued existence of the Greenwich fault
north of the Thames, while the distance between Greenwich and
Danbury is about thirty miles, in a straight line.
If, however, we turn our attention from faults to those folds in
the strata which Mr. Dalton has so thoroughly worked out in his
paper on "The Undulations of the Chalk in Essex" (Essex Nat., vol.
v., pp. 113-117), we may obtain, I think, some explanation of the
unusual height of Danbury and Tiptree Heath for this part of Essex.
It is well known that where beds are thrown into synclinal folds they
are usually better preserved than where they form anticlinal curves.
Outlying hills are, therefore, usually found where the strata lie in a
trough or basin, and consequently dip towards the centre of the hill,
not away from it. Now, if we draw a straight line along the axis of
Tiptree Heath, across Danbury, and prolong it in a south-westerly
direction, we find that it passes through, or close to, the equally
lofty Bagshot outliers of Stock, Billericay and Warley, each attaining
a height of more than 300 feet. Beyond Warley we soon reach the
broad flat of old river-gravel and alluvium which covers so much
ground north of the Thames. But if we prolong our line southward
of the Thames we find ourselves at Shooters' Hill (420 feet), the
O