lxvi 
PROCEEDINGS OF THE 
first section visited Hertford Castle, examining the old ruins and 
the “ Castle Mound” by the side of the River Lea. The present 
building is of comparatively recent date, but the original castle is 
supposed to have been erected in the time of Alfred the Great or of 
Edward the Elder. It was much strengthened at the time of the 
Conquest, and considerable portions of the boundary-walls still 
standing probably date from that time. 
On leaving the Castle the route taken was through the chestnut 
avenue in All Saints’ churchyard, and from there through Ralls 
Park (by permission of Mr. Eaudel Phillips) to Mr. Lines’s brick¬ 
fields near Rush Green. The second section came direct here by 
the London Road, the united party numbering between 30 and 40. 
The beds exposed at these brickfields and in an old chalk-pit near 
them consist of a small portion of the TJpper Chalk, with a very 
irregular surface due to its unequal chemical dissolution ; the usual 
layer of flints with some flint-pebbles in sand ; a very variable series 
of sands and clays representing the Woolwich and Reading beds; 
the basement-bed of the London Clay with part of the London Clay 
itself; and above these stratified deposits an irregular bed of pebble- 
gravel filling up depressions in the London Clay. 
From a point where all these beds except the Chalk and its 
surface-layer of flints could be seen, the Director gave a brief 
description of them, prefacing his remarks with some general obser¬ 
vations on the London Tertiary Basin. 
It may, he said, be well to explain that the term “ basin ” is here 
used as a convenient expression for a series of beds originally de¬ 
posited horizontally and subsequently let down in the centre by 
the sinking of the subjacent strata. The London Basin, therefore, 
is not a hollow in the Chalk in which the Tertiaries were deposited, 
in which event the surface of the Chalk would be curved and the 
Tertiaries would be horizontal, but it is a series of strata the 
members of which are conformable to, or parallel with, each other, 
and have only a very slight curvature caused by a folding or waving 
of the strata, which occurred after, and probably soon after, the 
deposition of the Eocene or Lower Tertiary beds. The same move¬ 
ment which caused a slight sinking of the Chalk and Tertiaries 
under London probably caused the slight elevation of the Wealden 
dome in the Kentish area, or that may have been of earlier date, 
taking place during instead of after the Eocene period. It must 
not however be inferred that the Chalk, after its quiet deposition 
by organic agencies in an ocean-bed, remained submerged through¬ 
out its extent until the lowest Tertiary beds, the Thanet sands, 
were deposited upon it, for a considerable area of it at least was 
probably for some time dry land, rising from the bed of the 
ocean and being subjected to denuding agencies, such as rain and 
rivers, similar to those now existing. In this neighbourhood there 
is evidence of a large amount of chalk having been washed away, 
and of the flints having been washed out of it, broken up, rolled 
into pebbles, and dispersed over wide areas, before it sank alto¬ 
gether beneath the ocean. The Thanet sands are absent here, but 
