78 On the Sand-Pit at High Ongar, Essex.
I therefore still believe the sand in question to be what I
represented it; and as I suspect that its low position is due
to a state of things not yet realised by geologists, though
brought to their attention by rue nearly twenty years ago,
I venture to bring the subject to the attention of the Essex
Field Club; because, if my view of the case be correct, the
position of the water-bearing sands beneath the London Clay
in the neighbourhood of Ongar must be affected by it; and
because the case is, I think, probably a part of the same
problem which has received so important an illustration by
the features disclosed in the boring at Wickham Bishop,
which are described by Mr. Dalton in the 'Transactions' of
the Club for 1881; the (to all but myself) unexpected results
of which boring have caused the waste of a large sum of
money by the county ratepayers of Essex.
In a paper in the 'Philosophical Magazine' for the year
1864,4 I endeavoured to show that the entire system of hill
and vale, over that part of England which lies east of a line
drawn from the Bristol Channel to Flamborough Head, has
arisen from a horizontal displacement of the formations
ranging from the Jurassic to the Eocene inclusive, which
was caused by two groups of movements; one of which,
being the earliest, produced curvilinear contours spreading
outwards from three centres where the elastic force giving
rise to the feature rose from beneath; and the other of
which, being the later, produced rectilinear upthrows from
east to west, but was confined to the South of England.
The centres from which, by a radiating lateral thrust, these
curvilinear contours originated lie—one near Canterbury,
another near the western extremity of the Isle of Wight, and
the third in what is now the North Sea; and in the map to
the paper I showed how the two latter meeting each other
from opposite directions produced contours which crossed
those emanating from the Canterbury centre, the result of
this crossing being the valley system of Bast Anglia ; and in
illustration of the effect of this crossing I pointed out that
certain angles in the stream of the Thames thus caused were
4 'Philosophical Magazine,' ser. 4, vol. xxvii., p. 180 (March, 1864).