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dull, with a greasy feel, and an earthy fracture. It yields to the nail, and affords a shining streak. It scarcely adheres to the tongue; becomes translucent when placed in water, and falls into a pulpy impalpable powder, without forming a paste with it. The blue Fuller's Earth is frequently of as good a quality as the yellow, for particular purposes, as in fulling coarse cloths, but the yellow is usually esteemed the better.
The general thickness of the veins is from 18 inches to 3 feet. If good, a vein 18 inches in thickness could be worked with profit, but not if of less thickness. Sometimes the vein stops suddenly; at others it gradually thins out.
Shafts were formerly sunk in the Fuller's Earth south of Bath to a depth of 20 or 30 feet, with levels. It was then much used in fulling at the cloth mills at Bradford-on-Avon, Frome, and in Gloucestershire. It is now, however, rarely if ever worked in the district.
The total thickness of the Fuller's Earth in Somersetshire is from 120 to 150 feet. Nodules of indurated marl sometimes occur in the lower beds.
The Fuller's Earth is largely developed in Dorsetshire (400 feet), but entirely disappears when traced beyond Gloucestershire; it does not extend beyond Burford on the borders of Oxfordshire. In Gloucestershire it has a thickness of 128 feet at Wotton Underedge, 70 feet at Stroud and Sapperton Tunnel, and occurs as a thin band at Cheltenham. The upper layers are frequently interstratified with beds similar to Great Oolite. (See fig. 15, p. 176.)
Amongst the fossils of the Fuller's Earth may be mentioned Ostrea acuminata, O. rugulosa, Avicula echinata, Pecten vagans, P. lens, Pholadomya truncata, Goniomya literata, Homomya Vezelayi, Isocardia concentrica, Ceromya plicata, Terebratula globata, T. perovalis, T. ornithocephala, and Rhynchonella media (varians).
Mr. R. Tate has estimated the number of species at 93; he regards the deposit as the uppermost zone of the Inferior Oolite.
The Fuller's Earth throws out copious springs, and causes numerous slips on the declivities of the hills around Bath.
The Stonesfield Slate comprises shelly oolites, gritty limestones, and laminated calcareous sandstones or flags, which, splitting readily along the planes of bedding, produce the so-called slates of Stonesfield. In some places the Stonesfield Slate passes into an oolitic freestone, as near Burford and Windrush. False-bedding is often met with.
The formation is rich in fossil Plants, Corals, Echinoderms, Molluscs, Fishes, Reptiles, and Mammals.
The Mammals include the Amphitherium, Phascolotherium, and Stereognathus; the Reptiles include Megalosaurus, Teleosaurus, and Testudo; the Fishes include Pholidophorus, Lepidotus, Pycnodus, Ganodus, Hybodus, Nemacanthus, Ceratodus, &c. Amongst the Mollusca are Rhynchonella concinna, Trigonia impressa, Gervillia acuta, Ostrea acuminata, &c. The plant-remains include Algæ,
Ferns, Cycads, and Conifers.
The flaggy beds are quarried in the Evenlode Valley, at Sarsden, Woodstock, on Sevenhampton Common, Eyeford, &c.; and the freestone beds at Burford and Windrush. Thus, as Mr. Hull remarks, in some places the beds yield 'slates' for roofing-purposes, in others blocks of stone for building.
The deposit worked for slates is sometimes only a foot in thickness, but it generally consists of two fissile beds of a buff-coloured or grey oolitic limestone called pendle, each about two feet thick, separated by a bed of loose calcareosiliceous sandstone called race, about the same thickness.
Concretions are frequent in the latter, and are called whimstones or pot-lids; they are partially oolitic, sometimes blue in the centre, and vary from six inches to two feet in diameter; their form is generally that of a flattened sphere; they do not break concentrically, but into parallel planes; and they often contain shells. The pendle, after being quarried, is suffered to lie exposed to the action of a winter's frosts, and the blocks being then struck on their edge with a mallet, freely separate into slates sufficiently thin to afford a light material for roofing. The quarries are principally situated in the valley immediately to the south of Stonesfield village, which branches off eastwards from that of the Evenlode. The mode of working is by driving horizontal galleries about six feet high into the side of the hill, and then extracting the two strata of pendle laterally, piling up the refuse masses of the intermediate bed of race, so as to support the roof: deep perpendicular shafts communicate with these galleries. These workings have been carried on from remote times to a considerable extent, so that both sides of the valley are completely honey-combed by them. Beautiful plumose stalactites are often found in the fissures of the rock, and are called by the workmen, from an obvious though coarse analogy, tallow. (Conybeare and Phillips.)
Upper Estuarine Series.
Above the Lincolnshire Oolite is a series of blue and grey laminated marls, clays, and shales, 15 to 30 feet in thickness, containing wood and other plant remains, and species of marine and freshwater mollusca. This has been termed by Mr. Judd the Upper Estuarine series. At the base is a ferruginous band rich in fossils.
Mr. Sharp observes that the Upper and Lower Estuarine series occur together in vertical juxtaposition throughout a
large part of Northamptonshire and in Oxfordshire. Oxfordshire he observes that the Upper Estuarine series is traceable to the Stonesfield Slate, and the difficulty of separating the two Estuarine series led formerly to the Northampton sand (Lower Estuarine) being regarded as the equivalent of the Stonesfield Slate. Among the fossils are species of Pholadomya, Modiola, Ostrea, Cyrena, Unio, &c.; remains of Cetiosaurus also occur in the beds.
All the characters presented by the Upper Estuarine series, according to Mr. Judd, point to the conclusion that they were accumulated under an alternation of marine and freshwater conditions, such as occurs in the estuaries of rivers.
In the north-western part of Lincolnshire the Rev. J. E. Cross has described clayey beds about 40 feet in thickness as resting upon the Lincolnshire limestone. They contain Ostrea subrugulosa, &c.; also fish-remains.
The Clays in this series are worked for brick-making. The soil is comparatively barren.
The Great or Bath Oolite consists of a series of shelly limestones (rags) and fine oolites or freestones, often exhibiting much false-bedding, and generally of a yellowishwhite colour.
The Great Oolite is rich in univalve mollusca, such as Alaria, Cylindrites, Nerinaa Voltzii, Nerita, Patella rugosa, Purpuroidea Morrisii; amongst the bivalves are Ceromya, Cypricardia, Gervillia, Trigonia costata, Pholadomya, Tancredia brevis, Astarte excavata, Arca, Ostrea gregarea, Pecten lens, Lima cardiiformis, and Opis lunulatus. Cephalopoda are not abundant. Amongst the
Brachiopoda are Rhynchonella concinna, Terebratula perovalis, T. digona, &c. The Coral, Eunomia radiata, is common near Bath.
The Great Oolite series in the neighbourhood of Bath was thus divided by Lonsdale :—
(1. Coarse, shelly limestones
Upper Rags. 2. Tolerably fine oolites
3. Tough, brown, argillaceous limestone
Fine freestones .
Lower rags, Coarse, shelly limestones
The Bath stone, as is well known, hardens on exposure after it has been quarried. In its natural bed it is soft and moist, and Professor Ansted states that a cubic foot of Bath stone will absorb one gallon of water. According to E. Owen, who wrote in 1754, there is no stone that differs so much in its bed, and after it has been wrought and exposed to the air, as the Bath free-stone. While it is in the ground, it is soft, moist, yellowish, and almost crumbly; and it seems very little more than congealed sand, and that not well concreted together. But when it has been some time exposed to the air, and is thoroughly dry'd, it becomes white, hard, firm, and an excellent stone.'
The beds are largely quarried, or mined, near Bath (on Combe, Bath Hampton, and Farleigh Downs), at Box and Corsham.
Some of the beds, called Weather Stones (brown shelly oolitic limestones), are specially valuable for plinths, cornices, &c.; the Scallet is of superior quality, being of very fine The absence of fossils renders the rock more valu
able as a freestone.
At Minchinhampton there are extensive quarries (Hampton stone), showing 30 to 40 feet of rock. The beds are also worked at Chalford, Brimscombe, Burley, &c. The soil is a loose stone-brash.