"WATFORD XATUEAL niSTOr.Y SOCIETY. XX VU 



the Upper Chalk, the bed forming the basement of the Tertiary- 

 Series. Another interesting point connected with the chalk here 

 was that it contained very little silex, for it had segregated in the 

 form of flints ; while, in the Lower Chalk, or chalk without flints, 

 the silex was probably distributed through the mass. Mr. Lines, 

 who here Joined the party, stated that in the bed of green-coated 

 flints, sharks' teeth and oyster shells {Ostrea Bellovacina) were 

 frequently found. 



Various sections exposed in the brickfields were then examined, 

 the Professor explaining the relative position of the different beds, 

 and their relations to each other, and to beds elsewhez'e which are 

 here wanting.* In this district we had, he said, the lowest portion 

 of the Tertiary Series seen north of London, but not the lowest 

 known in the London area, for while the Tliauet Sands were being 

 deposited south of the Thames, the Chalk here was nearer the 

 surface, not allowing of their deposition. The Woolwich and 

 Reading Beds also were only partially represented. They con- 

 sisted here of alternations of sands and clays, and showed a very 

 different set of conditions to that on the south of London, where 

 there were thirty or forty feet of ash- coloured sands. Here also, 

 there were no freshwater shells, though these beds were contem- 

 poraneous with the freshwater beds found at Lewisham, etc., 

 which contained a great number of shells ; for, while south of 

 London there were freshwater and estuarine conditions, in the 

 north and west of the London Tertiary Basin the deposits were 

 entirely marine. 



Other beds, which form a passage between the Woolwich and 

 Reading Series and the London Clay, were next examined, and 

 Professor Morris stated that they represented an important change 

 of conditions.' Their black flint-pebbles were interesting as being 

 derived from unworn flints perfectly rolled on some sea-shore, 

 and, after being rounded, spread over the surface where they 

 were now found. These higher beds, forming the basement-bed 

 of the London Clay, evidenced a great depression of a very large 

 area, extending between Marlborough, Hungerford, and Harwich. 



From the brickfields the route lay across the fields to the hamlet 

 of Hertford Heath, the highest point visited during the day, where 

 excavations are being carried on under the direction of Messrs. 

 Smith & Austin, of Hertford, for a reservoir to supply the 

 village with water. Here the Professor continued his lecture on 

 the geology of the neighbourhood. Few districts were, he said, so 

 interesting geologically as this, which had been partly worked out 

 by Professor Hughes. f Other heights of the same level were seen 

 around, and these elevations were the remnants of a surtiice of 

 uniform height which had been cut into deeply by denudation, the 



* A detailed account of the entire section exposed in these brickfields will be 

 found in the lecture by Professor Morris, on '-The Physical Structure of the 

 London Basin," in the ' Transactions,' Vol. I, p. 99. 



t See ' Quart. Journ. Geol. Soc.,' vol. xxiv, p. 283. 



