92 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Near Hertford (section fi'om chalk-pit and pits in the brick-field). 

 PI. I. Diag. C, Loc. sect. 2. 



Feet. 



Mixed clay and gravel 1 



I. Basement-bed f b. Brown sandy clay laminated with tougher clay, con- 



of the London < taining casts of /'awojoffla, &c 6 



Clay, Q)\ feet. [a. Flint-pebbles in clay OJ 



fy. Light greenish sand 4 



Ie. White or ash-coloured sand 6 



<f. Light yellow sands 4 



Reading Series, ■{ c. Light-coloured mottled red and grey clays 10? 



52 feet. b. Yellow sand with patches of the Ostrea Bettovacina in 



places at its base 6? 



ji. Green-coated flints 1 



39-'- 

 Chalk 12'' 



At Seacombe and Collier's End, north of Hertford, mottled clays 

 seem altogether to replace the sands (PL I. Diag. C, Loc. sect. 1). 

 The section at the latter place is peculiar from the circumstance of 

 the flint-pebbles, which usually form, with the quartzose sand, the 

 shingle bed at the base of this series, being here enveloped in, and 

 forming part of, the mottled clays, which therefore come down in 

 actual contact with the chalk*. To the south of Hertford, on the 

 contrary, sands predominate, as at Northaw, which is noted for its 

 fine bed of the Ostrea Bellovacina (PI. I. Diag. C, Loc. sect. 3). 



The mass of lower tertiaries capping the chalk hills between Ware 

 and Bishop Stortford affords no good sections. Several small pits, 

 of which that at Patmore Heath is the best, show the prevalence of 

 mottled red clays with sands and pebble beds. 



Patmore Heath, three miles west of Manewden. 



Feet. 



Brown clay and gravel 1 



Mottled red, brown and grey sandy clay 2 



Ash-coloured sand with laminae of brown clay and a seam of flint-pebbles ... 2 3 



Fhnt-pebbles in light greenish grey clay 1^- 



The Chalk crops out at about 6 feet lower. 



I am doubtful whether the Thanet Sands range thus far north. If 

 they do, they must be represented by the bed of sand which is to be 

 seen reposing on the chalk in a few pits between Bishop Stortford and 

 Newport. The sections, however, are so far between and so mdistinct, 

 that throughout Essex I do not know of one satisfactory exhibition 

 of the Lower London Tertiaries ; still enough is shown to lead to the 

 belief that sands there prevail in this series almost exclusively. In 

 Suffolk there are a few sections in the neighbourhood of Hadleigh 

 and Ipswichf, where it appears that the space of 30 to 40 feet be- 

 tween the London clay and the chalk is occupied by sands only ; 

 but whether they belong to the Woolwich beds or to the Thanet 



* This is the only spot in which I have seen the mottled clay come directly 

 into contact with the chalk. Elsewhere it is always separated by a few feet of 

 sand, gi-een sand, or ferruginous clay. 



t For sections of these pits at Gestingthorpe, Hadleigh, Ipswich, and Kyson, see 

 ray former paper in Quart. Journ. Geol. Soc. vol. vi. pp. 271, 272. 



