On the Sand-Pit at High Ongar, Essex. 
81 
1881 (Plate I.), compiled from tlie evidence of borings, 
inclusive of that of the Asylum Committee, which he had 
collected in his official duty as Geological Surveyor of that 
part of Essex, shows that the flexure in which this ridge has 
originated is precisely what by these dotted lines I had 
hypothetically anticipated, though I of course could not tell 
at what depth from the surface this flexure would bring up 
the base of the London Clay. 
Now, since the line of the Eoding Biver from Woodford 
to Ongar follows that of the arc of the Canterbury series, of 
which the rolling ridge at Wickham Bishop is a part, and the 
angles made by that river in its course are due to the crossing 
of the arcs of that series by those of the Isle of Wight and 
North Sea centres in combination, as already mentioned, it 
appears to me that if the sand of the High Ongar Pit be the 
Bagshot, it must owe its low position to a similar flexure or 
roll to that giving rise to the Wickham Bishop ridge, and 
caused by the lateral displacement of the strata which resulted 
from the radiating thrusts in which the arc-configuration 
originated. 
With this the high inclination exhibited by the stratifi¬ 
cation of the High Ongar Sand corresponds ; and this 
inclination being from E.N.E. to W.S.W., it would show 
that it is to the thrust from the northern centre that the 
flexure or roll is due. Although the present case is one in 
soft strata, yet the diagram given in the plate to the paper in 
the ‘ Philosophical Magazine ’ to illustrate the removal of the 
folds by denudation in hard strata best illustrates it; and to 
afford the means of comparison I annex a line of section 
(Fig. 2), drawn from the Lower Bagshot of Norton Heath, 
through the High Ongar Pit, to the Boding, in which also 
the position of the Glacial Beds occurring there is shown. 
I do not know the precise elevation of the pit, but estimate 
its bottom as upwards of 100 feet below the base of the 
passage beds from the London Clay to the Bagshot Sand, 6 
6 In mapping geologically the Ordnance Sheet 1, I included these 
passage beds in the Bagshot; but the gentlemen of the Geological 
Survey prefer to include them with the London Clay, which causes a 
G 
