102 ON THE NATURE OF GRAVEL PATCHES IN ESSEX.
Brentwood and the Westleton Beds, but more analogous to the
former." Of the patches of Westleton Beds in the counties west and
south-west of Essex the space at my disposal will not allow me to
speak.
Granting the identification of these various gravel-patches as
Westleton Beds, it becomes evident that they gradually increase in
height as we trace them further and further inland, being seen on the
coast at the sea-level and rising to heights of 500 and 600 feet in the
west. Then as regards their relation to the Glacial Beds. This is
excellently illustrated by a section drawn by Prof. Prestwich from the
valley of the Thames below Wallingford, through Stanmoor, Tot-
teridge, High Beach, Ongar, Braintree and Hadleigh to Southwold.
Near the coast the Westleton Beds are seen to underlie the deposits
of Glacial age. At Braintree the Westleton Beds "stand up through
the Boulder Clay and gravel which wrap round their base and partly
surmount them. They have there been disturbed and faulted before
the intrusion of the Glacial Beds, which have deeply eroded them."
While on the hills near Epping they cap the London Clay, and the
Boulder Clay lies from 80 to 100 feet lower down the slope.
Our author is of opinion that from the uniform character and
marine origin of the Westleton Shingle it must originally have been
formed on a nearly level sea-floor. The area in which it had been
deposited then became so unequally elevated that while the Westleton
Beds remained at nearly their original level towards their eastern
margin they became gradually raised to higher and higher levels
towards their western. The overlying Glacial Beds were thus
deposited directly above them at and near the coast, while on the
western border even of Essex the Westleton Beds are found, as we
have seen, on much higher ground than that on which the Glacial
Deposits appear.
A map accompanying the paper shows the distribution of the
Westleton Beds and of the other pre-glacial drifts, the Brentwood and
Southern Drifts. Of course in a brief notice of this kind, many
points of interest must necessarily be omitted. But enough has
already been said to mark the importance of Prof. Prestwich's latest
contribution to our knowledge of the newer rocks of south-eastern
England, and to show that—apart from his theoretical conclusions—
his paper is of especial value to all students of the geology of Essex.
T. V. Holmes.