Thomas Webster

“ These horizontal beds have no agreement with any of those beneath the chalk, nor indeed with any others yet observed in Great Britain; their mineralogical characters, and their fossils, are peculiar and distinctive. The calcareous beds contain numerous petrifactions [errata 4] of freshwater shells, and in others are found marine fossils agreeing with those described by Lamarck in the strata of the Paris basin. But fortunately, the inspection of specimens from the basin of Paris enabled me no longer to depend upon conjecture only as to the similarity of these formations. ”

“ The inclined strata A, B, C, D, E, compose a range of hills that divides the island into two parts, extending from the Needles at the west end of the island to the Culver cliff at the east: at which places may be seen vertical sections at right angles to the direction of the range.
The stratum marked A, is chalk with flints, [2] which at the north side is in nearly vertical layers, the inclination becoming gradually less and less towards the south side, where they dip about 60°. ”

“ The several beds of these chalk strata, which vary in thickness from a few inches to several feet, are frequently separated from each other not only by layers of flint nodules but frequently also by a marl containing a considerable proportion of clay, and this substance also sometimes fills up the diagonal fissures which cross the strata. The workmen take advantage of this circumstance in quarrying the chalk. ”

“ For it is not only extremely improbable that beds of such materials should have been formed [errata 2] in any other manner, but a circumstance which I noticed in Alum bay renders certain the original position of the sand and clay strata. In one of the vertical beds, consisting of loose sand, are several layers of flints, extending from the bottom to the top of the cliff; these flints have been rounded by attrition; are from one inch to eight inches in diameter, and appear to have belonged to the chalk. ”

“ In England every part of our chalk is completely covered by vegetable soil, which although very thin on many parts of our downs or smooth hills, yet affords support to peculiar grasses and other vegetables, on which are pastured vast quantities of sheep. The chalk of Franco is said to contain 11 per cent. of magnesia, to which the barrenness may be owing. ↑ On the authority of Mr. Parkinson I notice that the supposition of having discovered a specimen of Trigonia in chalk is erroneous. This belongs only to inferior strata. ”

“ Such of them as have been recognised are found to belong to species now growing only in the torrid zone; thus adding to the evidence afforded by the animal remains of the great change that must have taken place in the climate. ”

“ They are abundant at Gurnet Point. ↑ Since the reading of this paper I have been favoured by the Rev. William Buckland, Prof. of Mineralogy, Oxford, with specimens of freshwater shells which he has collected at Hordwell cliff. They consist of the lymneus, planorbis, cyclostoma, and a bivalve resembling a freshwater mytilus. From the state of the fossils, and the nature of the stratum in which they were imbedded, they would appear to belong to the lower freshwater formation. ”

“ But having considered the cerithia as marine shells, he thought it proper, on finding a species among the freshwater shells, to regard this as of a distinct genus; founding the distinction not on any difference in its form, but on the difference of the water in which it had lived. ↑ The Egyptian pebbles are said to occur in a similar situation. ↑ A very fine example of one occurs in a specimen in the museum of the Geological Society, presented by Leonard Horner, Esq. ”

“ Chalk.Plastic clay.Coarse limestone and sandstone.Silicious limestone.Gypsum and marl, containing bones of animals, forming the lower freshwater formation.Marles of marine origin.Sand and sandstone without shells.The superior marine sandstone.Buhr or millstone formation without shells, and argillaceous sand.The upper freshwater formation, comprehending marles and buhrs with freshwater shells.Alluvium or earth of transportation, both ancient and modern, analogous to our gravel, &c. ”

“ This includes the firestone of Ryegate, and Kentish rag.Blueish black marl.Sand and sandstone, highly ferruginous, containing subordinate beds of clay, fullers earth, shale, bituminous wood, and limestone. This stratum forms the wealds of Kent and Sussex.A series of strata of shelly limestone, known by the name of the Purbeck stone, alternating with shale and marle. Some of the fossils of these strata strongly resemble freshwater shells: they appear to be the Cyclostoma, Planorbis, &c.Clay with gypsum.Portland oolite.
Clay with limestone and bituminous shale, containing the Kimeridge coal. ”