80 On the Sand-Pit at High Ongar, Essex.
system of "arcs"; and by hypothetical lines of diagram
section drawn as radii from the respective centres at Canter-
bury and in the west of the Isle of Wight, through the
concentric "arcs" of each of these two series, I showed the
flexure which ought to occur at each concentric "arc."
I also gave other diagram sections to show the way in which
I conceived the denudation had taken place near these
flexures, and in consequence of them; though here again
I fell into error respecting the connection of the Glacial Beds
with these flexures, which my subsequent researches on
these beds dissipated,5 such flexures having been formed
long anterior to those beds. The displacements caused by
the rectilinear disturbances are not flexures, but upthrusts,
as the Figures II. to V. of the Newer Pliocene paper show.
In a paper in the 'Geological Magazine' for 1866 (p. 348),
"On the Structure of the Valleys of the Blackwater and the
Crouch," having occasion to show the Glacial Beds in
relation to the ridge on which Wickham Bishop stands (and
which forms a most conspicuous portion of one of the "arcs"
of the Canterbury series), I gave a section through the
trigonometrical station at that place, and passing through
the actual spot where the boring was afterwards made by the
Committee of the County Asylum; and I therein described
this ridge as originating in the way mentioned in the 'Philo-
sophical Magazine,' and by dotted lines in the section through
Wickham Bishop thus given (Fig. 9 of the Plate at p. 348
of the 'Geological Magazine' for 1866), showed the flexure
or roll over which I conceived must be concealed in it.
At that time no boring had been made to disclose this
structure, or, if there had, nothing was known to me of
such ; and I was led thus to depict what the unfortunate
boring afterwards disclosed by no other evidence whatever
than the hypothetical one of the case made out by the
paper in the 'Philosophical Magazine.' The section, however,
given by Mr. Dalton in the 'Transactions' of the Club for
5 In referring the flexure at Wickham Bishop to a movement beneath
the Glacial Sea, Mr. Dalton has, in his communication to the Club in
1881 ("The Blackwater Valley," Trans. Essex F. Club, vol. ii., p. 15),
fallen into the same error that I fell into.