On the Sand-Pit at High Ongar, Essex. 83
The Committee of the Essex County Lunatic Asylum being
compelled to find further accommodation for their patients,
purchased a farm at Wickham Bishop, near Witham, exactly
upon the crest of one of the arcs from the Canterbury centre,
shown in the map to the above-mentioned paper in the
'Philosophical Magazine,' and sank a well for water. This
sinking proved to be a total failure, in consequence of the
bore passing through a fold in one of the flexures described
in my paper "On the Formation of the River and other
Valleys of the East of England," and shown as occurring at
every repetition of the arcs in the hypothetical diagram-
section, drawn through those spreading outwards from the
Canterbury centre, given in that paper.
A description of this bore, accompanied by a section in
illustration of it, by Mr. W. H. Dalton, F.G.S., appears in
the 'Transactions' of the Club for 1881 (loc. cit.).
The line of the diagram-section in the plate annexed to my
paper in the Phil. Mag. crosses the arc on which Wickham
Bishop is situated, about twelve miles W.S.W. of that place,
viz., at Galleywood.
In consequence of the very small linear extent of surface
occupied by them, these folds are mostly concealed ; and it is
only where an excavation, as at Barkway, near Royston,
chances to occur over them exactly, or a boring, as at
Wickham Bishop, happens to hit on one, that evidence of
their existence can be demonstrated; but the flexure, I
maintain, occurs continuously along every one of the arcs,
ex necessitate, as a result of the horizontal displacement
(caused by the radiating thrust) in which these arcs originated;
and it was with this conviction that, having occasion in the
'Geological Magazine' for 18677 to give in connection with
the Gravels of Essex a section through the ridge at Wickham
Bishop Trigonometrical Station, which forms one of the
Canterbury arcs, I explained its origin by reference to my
above-mentioned paper in Phil. Mag.; and in fig. 9 of the
7 ["On the Structure of the Valleys of the Blackwater and the Crouch,
and of East Essex Gravel, and on the Relations of this Gravel to the
Denudation of the Weald." Geol. Mag., vol. iii. (1866), pp. 348-351.—Ed.]