Dr. FiTTON on the Strata below the Chalk. 223 



altogether a very strong resemblance to the Travertine of Italy, The top is sometimes penetrated 

 by conical and nearly vertical cavities, encrusted with a yellowish stalaginitic coating. In the 

 Isle of Portland it is compact and continuous at the bottom ; but in other places the lower part, 

 and in some cases the whole, is resolved by decomposition into slaty strata. 



At Upway, on the north of Weymouth, the lower portion of the Cap consists of a series of 

 thin beds of limestone alternating with very thin courses of clay. In Portland, even where 

 most compact, it contains a few casts of a small species of Cypris ; and these seem to be 

 more frequent (perhaps because more easily detected) in the more fissile representatives of the 

 bed at Upway and Bacon-hall. In one or two instances I found in it obscure traces of small 

 univalves like those of Garsington and Combe Wood near Wheatley in Oxfordshire. 



In a nook or recess, called by the boatmen Bacon-hall*, upon the coast about a mile east 



of Lul worth Cove, the section of this part of the series was as follows: 



a. "5/acA: Z)«V<" of Portland. 



6. Cap, consisting of: 



i. Slaty limestone, divided by dark lines of stratification ; which at the lower part become more 

 distinct, and at last take the form of ii. 



ii. Dark grey indurated slaty clay ; one bed of which is nearly 2 inches thick. — Beneath it is 



iii. A thin flake of soft whitish limestone. 



c. Dirt. An indurated bed, of a light brown colour, 4 to 5 inches thick ; composed of argil- 

 laceous (and carbonaceous) matter, and including small fragments of stone. 



d. {Skull-cap ?) Limestone, somewhat botryoidal ; the more compact portions having a flat con- 

 choidal fracture ; 2 to 6 inches thick. 



e. Portland stone, abounding in the characteristic fossils, and including, about 6 feet from the top, 

 a band of flint, in detached masses, about 4 inches thick. 



10. ^^ Dirt" below the Cap. Immediately below the Cap in the Portland quarries, and conse- 

 quently separated from the "Black Dirt" by a thickness of about 8 feet, is another bed, also 

 called " Dirt " by the quarry-men, from 2 to 6 inches thick, but more uniform in its texture than 

 the former, resembling coarse silt or indurated loam, and containing in some places small frag- 

 ments of stone, but never such large masses as the " Black Dirt". This lower bed deserves especial 

 notice, from its affording specimens of Cycadeae, in an upright position, and partially immersed in 

 it, as if they had grown there. Of these I myself saw two in their original place at a quarry 

 called " the Wheat-croft ", on the east of the " Traveller's-rest " ; one of them about six inches 

 high, surrounded with the Cap, into the lower part of which it projected above the Dirt for about 

 half its thickness, so that it was necessary to cut away the stone to take it out ; and from the 

 existence of many other specimens in the debris of the same quarry, which the workmen assured 

 me had all come out of this bed, I believe them to be of frequent occurrence. Among the latter 

 was one of unusual size, larger indeed in its horizontal dimensions than any other specimen I have 

 seen, either from this bed or the Dirt above the Cap'|-. This, from its flatter form, may possibly 



* Notwithstanding the apparent firmness of this rocky coast, great changes are constantly in 

 progress there. An old boatman who conducted me, without having been asked a question, 

 expressed in very strong terms his surprise at the alterations produced, to his own knowledge, 

 within the last thirty years. 



f The specimen is now in the museum of the Geological Society. It is of an irregular figure 

 approaching to an oval, and measures 20 inches by 19 in its horizontal diameters, the vertical 

 thickness varying from 6^ to 9 inches. Another less perfect specimen which I saw in the same 

 quarry, was about 9 inches thick, and its diameters not less than 34 and 30 inches. Of the Cy- 

 cadeae from the Upper Dirt-bed very few exceed 10 inches, in height and horizontal diameter. 

 The largest I have seen is nearly 10 inches high, and about 12 in diameter near the bottom. 



VOL. IV. SECOND SERIES. 2 G 



