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is well suited for orchards and teazels. It was formerly largely used for marling ground: hence the number of old marl pits.
Alabaster or gypsum (hydrous sulphate of lime) occurs in abundance in some localities in the Red Marl or Gypseous marls of the Isle of Axholme, Newark and Orston, Nottinghamshire; Chellaston and Aston, Derbyshire; near Tutbury, Staffordshire; near Whitehaven, Cumberland; Syston, in Leicestershire; and at Watchet, in Somersetsbire.
The purer and variegated kinds are manufactured into ornamental articles, the common sort (but that most largely worked) is converted by burning into Plaster of Paris, which being largely used in forming moulds for the Staffordshire potters, the alabaster is known as Potter's Stone. The very coarse kinds are used as top-dressing for soils.
Celestine, or “Salt-stone' (Sulphate of Strontian), is found in some abundance in the Red Marl of Gloucestershire and Somersetshire.
Pseudomorphous crystals of rock salt occur abundantly in the Keuper sandstones and marls.
Fullers' earth is raised from the marl beds at Raddle Pits near Braithweel, north-east of Rotherham, also at Renton in Yorkshire; and at Taschbrook, one mile from Warwick, a substance probably of the same nature, as it was intended as a substitute for soap, was raised by the Earl of Warwick.
In Cheshire and Worcestershire beds of Rock-Salt occur, interstratified with the lower beds of the Keuper Marl. In Cheshire, Prof. Hull considers that the Marl has a thickness little short of 3,000 feet. Our culinary salt is largely manufactured from the brine springs. Hence the term • Saliferous' is sometimes applied to the Upper Keuper strata.
Among the localities are Droitwich and Stoke, in Worcestershire; Northwich, Sandbach, Anderton, Middlewich,
1 Cony beare and Phillips.
Lawton, Dirtwich, and Nantwich in Cheshire ; and Shirleywich in Staffordshire. Prof. Hull states that at Droitwich the salt has been extracted from the brine for upwards of 1,000 years.
The Rock-salt occurs at some places in a massive or granular form, at others in large cubical crystals ; Gypsum is often found with it. It is usually of a dull red tint, and associated with red and pale green marls. When lighted up with numerous candles, the vast subterranean halls that have been excavated during the working of Rock-salt, present an appearance which richly repays any trouble that may have been incurred in visiting them.?
In Nantwich and other places in Cheshire where the salt is worked, the beds containing it are reached at a depth of from 50 to 150 yards below the surface. The number of saliferous beds in the district is five, and they vary in thickness from six inches to nearly forty feet; a considerable quantity of salt is also mixed with the marls associated with the purer beds.
The descent to the mines is by a shaft, used for the general purposes of drainage, ventilation, &c. The roof, which is about 20 feet above the floor, is supported by pillars about 15 feet in thickness. The Wilton mine, one of
lò the largest, has been worked 330 feet below the surface, and from it, and adjacent mines, upwards of 60,000 tons of Rock-salt were annually obtained; a part of which was exported, and the rest dissolved in water, and afterwards reduced to a crystalline state by evaporating the solution.
The mines, however, are not the only sources from which salt has been obtained, and it is only since the year 1670, when the beds were discovered during an unsuccessful sink
1 The houses in which salt is manufactured are called Wych-houses.
2 For these and the following remarks I am indebted to Prof. Ansted's Geology (1814).
ing for coal, that the actual Rock-salt, as a mineral, has been dug out from the mine. Before that time the chief supply was obtained from the brine springs of Droitwich, near Worcester. (Ansted.)
In the Marston mine, near Northwich, there are two thick beds of Rock-salt; the upper 84 to 90 feet, the lower 150 feet in thickness, and they are separated by 30 feet of indurated red clay containing strings of salt.
The Red marl is not a fresh water-bearing stratum. It is necessary to penetrate it before an abundant supply of water is reached ; and this is generally met with in underlying sandstones.
Mr. James Plant has given the following general section of the Upper Keuper Beds at Leicester :d. Upper Keuper Marls, containing beds of gypsum and
several thin bands of green marly sandstone, on which were found numerous pseudomorphous salt
crystals. 80 to 120 feet. b. Thin sandy shales, with “way-boards' of green marl.
25 to 30 feet.
20 to 30 feet.
The total thickness of the Keuper series near Leicester is from 700 to 1,000 feet. The water-stones are worked for building purposes.
The Red Marls are largely worked for brick-making near Nottingham.
It is needless to indicate the particular geographical distribution of the Triassic rocks, as they can best be seen by
1 The 'Red Clay of Tuxford' belongs to the series.
reference to a geological map. They form part of the plain of York, and stretch through Nottinghamshire, Leicestershire, Derbyshire, Cheshire, Staffordshire, Warwickshire, Worcestershire, and Gloucestershire, and there is an outlying mass near Carlisle, consisting, according to the Rev. P. B. Brodie, of red marls and water-stones.
TRIASSIC ROCKS OF SOUTH WALES AND THE
SOUTH-WEST OF ENGLAND.
In Glamorganshire, Gloucestershire, and in the neighbourhood of the Mendip Hills the Red Rocks consist of Dolomitic Conglomerate, Dolomitic Limestone, Sandstone (generally very calcareous), and Marl.
The Dolomitic Conglomerate, sometimes called Millstone' or · Millgrit rock,' is an old beach deposit of Keuper age, derived chiefly from the Mountain Limestone. It rarely contains pebbles from the Old Red Sandstone, Millstone Grit, or Coal-measure Sandstones, partly because they are not so extensively exposed along the old margins, and partly because most of the sandstones would be of too friable a nature long to resist the friction to which they were subjected.
The included fragments are sometimes well-rounded, but often so slightly worn as to constitute, in fact, a breccia rather than a conglomerate. They vary in size, from that of a pea to boulders two or three feet in diameter; but stones about the size of a hen's egg constitute by far the larger proportion of fragments in the conglomerate. These cemented together by the Carbonates of Lime and Magnesia, whence the name Dolomitic or Magnesian Conglomerate. Very frequently the cementing material is simply Carbonate of Lime, sometimes it is marl or ferruginous sand; the matrix is usually mnch coloured by peroxide of iron.
The thickness of the Conglomerate is subject to much variation : it is rarely more than 30 feet.
The Dolomitic Conglomerate is sometimes burnt for lime. It is also used for building and ornamental purposes. The Draycot stone dug near Axbridge is well known in the district.
The Dolomitic Conglomerate usually occurs at the base of the Red Marl, and vet at the same time it occurs at all horizons along the margin of that deposit, where the beds dovetail one into the other, proving that its formation continued throughout the entire series. (See Fig. 8, p. 84.)
Sandstones occur near Brislington, Chew Magna, and Yatton (Claverham or Clarham stone).
At East Harptree beds of chert are associated with the marls and conglomerates.
The remarkably even manner in which the Mountain Limestone has been denuded is well shown at Wallcombe, near Wells, where the Keuper beds rest on the basset edges of this rock. This even line is also very conspicuous in the vales near Frome.
The road to Wookey Hole on the one side of Wells, and that leading to Dulcot on the other, show in places in the Red Marl a bed called the Wonder Stone,' described by Messrs. Buckland and Conybeare as a beautiful breccia, consisting of yellow transparent crystals of carbonate of lime, disseminated through a dark red earthy dolomite.'
Beds of Dolomitic or Magnesian Limestone are conspicuous near Clevedon, and on the Glamorganshire coast.
Red and brown oxides of iron are not uncommon in the Dolomitic conglomerates, and they have been worked in many places, as at Llantrissant in Glamorganshire, on the Mendip Hills, &c. Reddle has been largely dug near Winford.
In the Dolomitic Conglomerate of Durdham Down, near