82 On the Sand-Pit at High Ongar, Essex.
the level of which base, where not covered by the chalky clay
(as it is covered at Norton Heath), ranges between 240 and
260 feet above Ordnance datum, and is to be found uncovered
by that clay near Frierning, Kelvedon, Hatch Common,
Shenfield, Brentwood, South Weald, Havering, and Lam-
bourne End on the east, and Epping and High Beach on the
west of the Roding.
Fig. 2.—References to beds the same as in Memoir on the Newer
Pliocene Period in England, viz.:—V. London Clay. VI. The Lower
Bagshot. VIII. Pebble-beds of uncertain age—probably Diestian (oldest
Pliocene), and if not so, of Bagshot age. e. Gravel of the Glacial
emergence, d. The Chalky Clay. N.B.—There is some gravel also in the
Roding Valley-bottom, but it is intermittent and Post-Glacial.
Appendix.
Note on Mr. W. H. Dalton's Paper on the "Blackwater
Valley, Essex."
[Mr. Wood kindly presented to the Library of the Club a
copy of his paper in the 'Philosophical Magazine' for March,
1864 (vol. xxvii. (Ser. 4), page 180), entitled "On the Forma-
tion of the River and other Valleys of the East of England,"
adding thereto in MS. the following remarks (dated December,
1883) upon Mr. Dalton's paper (Trans. Essex F. Club, vol. ii.
(1881), p. 15). As these observations appear to be very
pertinent to the subjects treated of in the paper on the Ongar
Sand-pit, we print them here, with a few verbal alterations,
by permission of the author.—Ed.]
considerable variation in our respective delineations of the Lower
Bagshot beds in Essex. The alternations of the sand with the brick-
earth (or loam) layers in these passage beds are so inconstant that no
other line than that which the lowest sand-bed anywhere gives will, in
my opinion, serve for a division-line between the London Clay and the
Bagshot Sands, the one being merely a continuation of the other by the
shoaling of the sea-bottom.