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, 6 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 Y. of the Newer Pliocene paper show. 
In a paper in the ‘ Geological Magazine ’ for 1866 (p. 848), 
“ 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. 848 
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 1 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. lo), 
fallen into the same error that I fell into. 
