tinguishable from those of other formations. The character of yellowish white calcareous freestone, generally mixed with a small quantity of siliceous sand, being common to all their varieties, and nearly all of them becoming occasionally oolitic. The varieties to be observed in the Upper series, or that of Aylesbury and Portland, are, a fine grained white oolite, a loose granular limestone of earthy aspect and of various shades of yellowish grey; and more rarely a compact cretaceous limestone having a conchoidal fracture. In Wiltshire and Dorsetshire, many of the beds contain layers of chert alternating with them like the flints in the chalk formation; the lower beds are very sandy, and often very abundant in green particles resembling those of the green sand. Nodular concretions of calcareo-siliceous grit occur in the sandy beds in Oxfordshire. (C.) The more oolitic varieties (principally quarried in the Isles of Purbeck and Portland) afford the great part of the stone used for architectural purposes in the vicinity of London. Mr. Webster gives the following account of the Portland quarries. The uppermost beds of the isle of Portland consist of an oolitic rock, and they are numerous. That which appears on the summit, and is called the Cap, is of a yellowish colour, and porcellanous character; it is only burnt for lime. The next bed is worked for sale, being the best building stone. Those below this bed contain numerous casts of shells that injure the stone, which is only used for coarser purposes; and with these beds alternate others censisting of chert. (W. p. 197.) * * A more detailed account of the several quarries in the Isle of Portland may be seen in the Monthly Magazine for Jan. 1813, p. 481, whence the two following Sections are copied. Section of Waycroft and other Quarries on the East side of Portland. 1. Vegetable mould, less than 2. Stone brash, a cream-coloured limestone. 5. The White bed, or the highest layer of marketable stone: two 6. The Middle bed of marketable stone, containing few marine 7. The third bed with few or no shells; this is the best stone, and it varies in thickness in the several quarries from . ... 7 to 14 43 (bb) Mineral contents. The beds at Portland and Tisbury contain beautiful yellow sulphate of barytes (sugar candy stone) and crystallized calcareous spar. (G. Notes.) In the next quarry, the third bed (7) is in two layers; the lower of these is free from shells, except about one foot of its top, and the upper one contains very few shells. We visited four other quarries on this side of the island; but as they do not differ materially from the above, it would be improper to repeat my observations. Under the foregoing marketable stone, many layers of flint and unserviceable stone, to the depth of about 50 feet. On the east side of Portland, the whole thickness of the stony strata, is about 93 feet, and beneath that is black blue shiver of great thickness. Sections of Quarries on the West side of Portland. In the first quarry we visited, I found the vegetable mould, the stone brash, and the beds of hard stone cap, similar to what they are on the cast side of the island. But in this place the marketable stone is about 11 feet thick, in one bed; whereof about 24 feet of the top is egg-shaped. In the adjoining quarry immediately under the Cap (4) is Roach (a mass of fragments of oyster shells compressed and cemented in a very hard stone) six feet thick, upon a bed of the best saleable stone nine feet thick. The third quarry is similar to the two former, down to the Roach, which in this case is five feet thick, and united to the best stone without any parting. In this quarry the Roach was cut into blocks and sent to Millbank, Westminster, for building the abutment of Vauxhall bridge. And many others of these blocks were prepared for the same purpose, but they remain in the quarry at this time. (Aug 1812.) In the fourth quarry the Roach is in the same state as in the third quarry, but reduced to three feet thick, and at this place the best stone is 11 feet." feet. In Gosling's quarry, the stone brash and two beds of the Cap, 20 6 5. White bed, a marketable stone, exclusive of the two feet of Roach which are united to it... 8 Many layers of flint and stony rubbish, including one bed of a white tender stone, which is not fit for great exposure 6. Two other beds of Roach in the place of the middle bed of saleable stone. 6 ...... 6 7. The Third bed (7) of saleable stone, contrary to the usual order, is not near such good stone as the White bed (5) in this quarry ..... The above marketable and other stone lies upon many layers about .... 6 .55 or 60 The whole of the stony strata in this place is about 112 And under that is black blue shiver several hundred feet thick, whereof there are about 100 feet above the level of the sea. Middleton, Mo. Mag. Jan. 1813, p. 481. (cc) Organic remains. * (The references to figures where not otherwise specified, are to Sowerby's Mineral conchology.) By the Rev. W. D. Conybeare. A section of a more descriptive character, drawn up by Miss Bennett from the quarries excavated in this formation at Chicksgrove, in the vale of Tisbury, Wilts, is printed in Sowerby's Mineral Conchology, vol 2. p 58; we here subjoin it, presuming that the beds here called chalk are the cretaceous limestones mentioned in the text. A Section of Chicksgrove Quarry, South of the village and of the river, in the parish of Tisbury, in Wiltshire. 1. Top of quarry. Rubble, fourteen feet. No shells in this bed. (Impure chalk.) 2. Stone not good, two feet. The lower part of this bed contains the same shells as the chalk below it. 3. Chalk, two feet. Trigonias three species; Pectens like those of Thame, Oxfordshire; Ostrea several species; a thick equivalve; bivalve which is common in the rubble beds of freestone; a small bivalve, perhaps Unio; two other small bivalves, and a Trochus like those of the flinty chalk. (Hard chalk.) 4. Flint, four inches. (Approaching chert.) 5. Chalk, eleven feet. A rubbly chalk without shells. (Hard chalk.) 6. Spangle bed, five feet six inches. Contains Ammonites, Oysters, and various other shells changed into the spar. (Limestone containing some white, but no green sand.) 7. Walling Rag, two feet six inches. Fragments of shells changed into spar. (Like No. 6, only coarser and harder.) 8. Devil's bed, two feet. Fragments of shells changed into spar, smaller shells than the Walling Rag. (Like No. 6.) 9. Great Rag, three feet. No shells, or only small fragments. (A compact sandy limestone, with minute grains of green sand.) 10. Brown bed, three feet. Contains Ammonites. (Less compact than the last, with more green sand, some parts of a loose texture.) 11. Trough stone, three feet four inches. Trigonias, the shell changed into spar, and Ammonites. (Similar to some parts of the last.) 12. White bed, two feet eight inches. Contains Ammonites. (Between 10 and 13.) 13. Hard bed, three feet six inches. Trigonias, the shell changed into spar, and Ammonites. This bed is very like No. 11. (Rather less green sand than No. 10.) 14. Fretting stone, two feet. A soft stone and no shells. (A loose sandy limestone with green sand) 15. Under bed, two feet. Fragments of shells changed into spar. (More compact and finer grained than the last, and holding less green sand.) 16. Under bed, two feet six inches. Contains Trigonias, the cast of the outside of the shell a soft stone. (Like the last, except that it contains no spar.) The whole depth of Chicksgrove Quarry to the bottom of the stone is 61 feet four inches, measured by John Montague, foreman of the quarry. The scales of fish, erroneously supposed to have been found in this We believe that remains of fish are occasionally met with in this formation as well as in the preceding. The shells which occur are principally the following: CHAMBERED UNIVALVES. Ammonites triplicatus, T. 92, fig. 2. giganteus. T. 126. Of these shells, the Ammonites triplicatus and Pecten lamellosus are most characteristic. In the section of Chicksgrove quarry (see page 175), other particulars concerning the shells of this formation will be found. No other Zoophytal remains are mentioned than those of a beautiful aggregated madrepore, specimens of which, imbedded in a semitransparent chert, occur at Tisbury in Wilts. Large fragments of wood are common. quarry, were from a tile-stone quarry on Lady-Down, in the parish of Tisbury, and about one mile north-west from Chicksgrove quarry. The above are the names by which the different beds are known by the people who work the quarry. Most of the stone contains calcareous spar, in the place of the fragments of shells dispersed through it, but No. 14 and 16 are without it; the spangle bed contains most. The rare stratum called by geologists White freestone,' and here called chalk, but from which it differs in its situation, occurs also at Brill in Buckinghamshire, and at Upway in Dorsetshire. The sections presented at Brill hill in Buckinghamshire exhibit a remarkable coincidence with the above. (dd) Range and extent. (ee) Height of hills. Referred to the general article at the end of this section. (ff) Thickness. According to Mr. Middleton's measurements, these beds, in the Isle of Purbeck, exhibit altogether a thickness of about 120 feet; and this appears the estimate on which the greatest reliance may be placed. (gg) Inclination. Referred to the general article at the end of this section. (hh) Agricultural character. A poor stone-brash soil. (i) Water. The water issues abundantly from the bottom of this rock, where it is thrown out by the subjacent Kimmeridge clay. (aaa) Chemical and external characters. These beds consist of a blue slaty or greyish yellow clay (the Oaktree clay of Smith,) containing selenite; but it sometimes contains beds of highly bituminous shale, as near Kimmeridge on the coast of the Isle of Purbeck, where these are used as fuel, whence they have obtained the name of Kimmeridge coal; and hence the name of Kimmeridge clay as applied to the whole formation. The beds are most instructively displayed (G. Map) near that place. They are also finely exposed (G. Notes) on the coast of the Isle of Portland. On the east of little Kimmeridge, where the cliffs are abrupt, they are composed of a slate-clay of a greyish yellow colour, finely slaty, containing both animal and vegetable impressions. The plates of which the rock is composed, become much more evident after it has undergone some decay; or, when sound, after it has been exposed to the fire. It divides spontaneously into large tabular masses. The fracture of the rock is earthy, with many small specks and nodules of indurated clay. The outside of the rock is covered by a thin layer of calcareous spar. The mass effervesces with acids, but the nodules of indurated clay do not. This rock passes gradually into a bituminous shale; but the first transition is into a slateclay of a lighter or darker colour, the joints of which are covered with iron pyrites. It burns with a yellowish flame, giving out a sulphureous smell, and becomes afterwards of a light grey colour. The second transition is to a bituminous shale called Stony Coal [Kimmeridge Coal *] the specific * Near Smedmore in the parish of Great Kimmeridge, is found what the country-people call' Coal-money', generally on the top of the cliffs, two or three feet below the surface, enclosed between two stones set edgeways |