SESSION 1897-98. xxix 



Mr. Hopkinson then drew attention to the remarkably straiglit 

 line formed by the outliers on the north, by means of a strip of 

 paper twelve times as long as it was wide, on which he had drawn 

 nearly all the outliers which extend from Wargrave beyond 

 Maidenhead on the south-west, to Albury near Bishop's Stortford 

 on the north-east, a distance of fifty miles. They are almost 

 exactly in the line of strike of the Chalk, and he referred to the 

 theory tliat they mark a slight synclinal deflection in the dip of 

 the underlying strata. This line of Tertiarj' beds now forms the 

 liigliest land, so it was strange if it owed its preservation from 

 denudation at an early period, as was supposed, to having lain in 

 a hollow in the Chalk. At any rate, tlie existing outliers were 

 ])robably fragments of a once more-continuous band, and owe their 

 indiviihial preservation at a later period, and onwards to the 

 present time, to the greater resistance to subaerial denudation 

 ofPered by the gravel by which they are mostly capped than by the 

 Chalk by which they are surrounded. Most of the outliers east 

 of Datchworth he stated were of the Heading Beds only; the 

 ])atchworth outlier, not far from here, and others in a westerly 

 direction had upon these beds the London Clay, though sometimes 

 no more of it than its basement-bed. Here the Reading Beds consist 

 of sands with numerous clayey partings. The Chalk below is piped, 

 and the Tertiary beds above have been irregularly let down, giving 

 them quite a contorted appearance on the north side of the brickfield, 

 while on the south they are overlain by the London Clay, and, 

 althouiih not here seen, he thought it might be inferred that this 

 clay had so far prevented the percolation of water into the Chalk 

 that pipes are absent and the Heading Beds are but little disturbed. 



In the basement-bed of the London Clay, teeth of several species 

 of shark and casts of bivalve shells are sometimes to be obtained, 

 but the bed of flint-pebbles in which these occur was neaily all 

 covered up by debris. This is the lowest layer of the basement- 

 bed, but there is another layer of flint-pebbles near the top in 

 which oyster-shells are occasionally found. 



Drift gravels, wliich in one part are very similar in composition 

 to Westleton Shingle, were seen to cover the Tertiary beds, and to 

 h:ive boulder-clay resting upon them ; and in Griggs' Wood, 

 a little to the north and on the highest ground in the immediate 

 neighbourhood, a characteristic section of Westleton Shingle was 

 seen, and Mr. Salter pointed out the simple character of its con- 

 stituents and their similarity to those forming the gravels at South 

 Mimms, High Barnet, and other places on the main mass of the 

 London Clay. 



On leaving the brickfield Sherrards Park Wood was entered. 

 The trees were looking their best with the fresh verdui-e of spring, 

 and the walk of three miles through the wood to the pits near 

 Hatfield Hyde was much enjoyed. Here there is a very large 

 excavation by the side of the Great jS^orthera Railway, exposing 

 a depth of about 42 feet of Glacial deposits, consisting of an upper 

 bed of boulder-clay 12 feet in thickness with much chalk in its lower 



