286 Dr. FiTTON on the Strata below the Chalk. 



Ft. I. 

 8. Whitish beds of nearly uniform aspect. 



a. Soft fissile marl or limestone in about six beds ; the divisions, however,! 



ft. to/^ ° 



seem to be the effect of decomposition 3 



b. Uniform hard grit or sandstone, consisting of quartzose sand in a cal- I ^ ^ 



careous cement J 5 



9. Stony concretions, in greenish very fissile sandy clay ; — 3 to 5 beds ; passing into, and! ^ ^^ 



continuous with 10 ....J 



10. Fissile sandy matter ; and grey, sandy clay, passing into 11 1 C 



11. Fissile, tough, yellowish, sandy clay, containing much calcareous matter, and including 1 

 Cypris, Mytili, and Modiolae / 



{^Portland Stone.l 



12. Beds of good stone ; grey without, blue within. 



a. " Capping," full of shells ; like the " Roche " of Portland 8 in. to 9 



b. Solid stone, the best 



c. Soft stone, bluish, full of remains of shells; Ammonites giganteus; Exogyra 

 nana ; Ostrea, two species ; Plicatula 



Bottom of the Quarry 



The proportion of sand to the stone, in these quarries, is much greater than in those of the 

 coast, the Portland stone here appearing generally in the form of concretions in the sand : and this 

 is the case also in the Boulonnois. Near Dinton Castle the stone assumes the form of insulated, 

 subglobular, or potatoe-shaped concretions, containing great numbers of Oysters, with otlier 

 fossils. 



(151.) One of the most prominent circumstances in the upper part of the 

 preceding" sections, is the contrast between the arrangement of the sands and 

 Fuller's earth, or ochreous clay^ and that of the beds which represent the 

 Purbeck formation immediately below ; the upper surface of the latter being 

 commonly indented or eroded into cavities and inequalities, from a few inches 

 to four or five feet in depth, which are generally coated with a thin stratum 

 of clay, and then filled up with sand and gravel. These appearances, which 

 are perfectly analogous to that represented at p. 276, in the cut of the "Gulls" 

 of Great Hazeley, and to the discordance of the two sands at Swindon, p. 265, 

 are observable in all the pits of this country. They clearly show that an 

 interval must have elapsed between the deposition of the Purbeck strata and 

 that of the Lower green-sand, during which the surface of the former was 

 disturbed, by the operation no doubt of water. 



(152.) The tough clays, near the junction of the incumbent strata with 

 the Portland beds, are well seen in many of the pits of the lower country, 

 as at Bishopstone and Southwarp, and in the heights about Whitchurch and 

 Quainton. It is difficult or impossible, in some cases, to determine whether 

 they are to be referred to the Fuller's earth of the Lower green-sand, — to 

 some of the beds subordinate to the Weald-clay and Hastings-sand, or to the 

 Purbeck series. But it may be remarked that, although these clays alternate 

 with thin slaty limestone, which contain Cypris and other freshwater fossils. 



