shire, where is the well-known cavern called the "Blue John Mine."

Alum, a sulphate of alumina and potash, is largely obtained from the Upper Lias of Whitby, but is not confined either to that locality or to Liassic strata, for in Scotland it is procured from Carboniferous rocks. The Alum Shales of Whitby, which contain iron pyrites, are either exposed to weathering action or roasted, when the pyrites is decomposed and sulphate of alumina formed. The mass is then digested with water and the liquid treated with chloride of potassium, after which, with evaporation, crystals of alum are freely obtained.

One of the geological formations well developed in Somersetshire is named "The Fuller's Earth" from being largely made up of that mineral substance. Fuller's earth is, however, more commonly obtained from other strata that yield it in finer quality. The most important bed is, perhaps, that at Nutfield, in Surrey, where it occurs in Lower Greensand or Neocomian rocks, and whence it is sent in large quantities to the woollen manufacturing districts, where it is so much required for the dressing of cloth. In England, besides Somersetshire and Surrey, this valuable material is found in Kent, Bedfordshire, and Nottinghamshire, and may, like the finest terra-cotta clay and other valuable minerals, be met with in localities where now the only industry is agriculture.

The mineral produce of the United Kingdom is vast, but were landed proprietors more fully acquainted with the geological structure of their estates, the aggregate annual money value of the minerals obtained from British rocks would be greatly increased. From what has now been said, it will be seen that the mineral treasures of these islands are not confined to a few

localities, or restricted to one or two rock formations. Indeed, it is not too much to say that there is no part of the United Kingdom where minerals of economic value may not be found, and on many estates, in purely agricultural districts that were only expected by their proprietors to yield the produce of their surface soils, mineral substances of great value have been discovered by a knowledge of the underlying rocks.

J. LOGAN LOBLEY.

CHAPTER LXXXIII.

LAND AND STONE.

BY PROFESSOR J. LOGAN LOBLEY, F.G.S.,

Professor of Physiography and Astronomy, City of London College; Lecturer on
Geology, Crystal Palace School of Engineering; Vice-President of the City of London
College of Science Society; Member of the General Committee of the British Association;
Member of the Geologists' Association; Hon. Member Hamp. F. C.; etc.
Author
of "The Study of Geology," "Geology for All,” "Mount Vesuvius," "Hampstead
Hill," "The Inter-relations of the Field Naturalist's Knowledge," "The Cretaceous
Rocks of England," ""The Causes of Volcanic Action,"
""The Origin of Gold," etc.

FACILITIES for the conveyance of building stone from remote rural districts have been so greatly increased by the development of our network of railways, that many estates have been rendered thereby of greater potential value. Very much agricultural land is over rocks containing beds of excellent building stone, that could now be without difficulty taken to large and growing towns where good stone is in constant demand.

In olden times the building materials furnished by a district were almost exclusively used for the edifices erected there. Thus in a chalk country the old churches are of the harder beds of the chalk or of chalk flints, in a sandstone country of sandstone, and in a limestone district of limestone. The ancient buildings of the south-east of Yorkshire and the north of Nottinghamshire are of magnesian-limestone, and the older colleges of Oxford are built of the Coral Rag from the neighbouring Headington Hill. The extensive use of Purbeck marble

for the churches and cathedrals of the Early English period was an exception to the rule, for this stone was so highly valued by the mediæval ecclesiastical builders that great expense was incurred in obtaining it, and hence it was taken so far north as Lincoln, where it is conspicuously seen in the glorious minster of that city.

Building materials are now brought from long distances, and so there is a greater variety of stone seen in modern buildings, especially in London, but still there is much less variety than there might be, for sandstone as a building material is little known in the south of England, and limestone for building purposes is not used in the north.

The handsome buildings of Edinburgh and Glasgow, of Newcastle-on-Tyne, of Leeds, Bradford, and other towns of Yorkshire, as well as the houses generally, are built of the fine light-coloured SANDSTONE of the Carboniferous rocks. At Craigleith, in Mid-Lothian, this stone has been worked very largely, the New Town of Edinburgh being almost entirely built of it. Carboniferous sandstones are also extensively quarried in Yorkshire and Derbyshire, and from them in the former county are obtained, besides the free-stones, the flag-stones so much used for pavements, landings, etc., called "Yorkshire Flags."

Of sandstones, next to the Carboniferous, perhaps the Triassic are the most used. In south-west Lancashire, in Cheshire, and in Staffordshire, Shropshire and Warwickshire, the Triassic, or New Red, sandstone is very largely quarried for building stone. Most of the public buildings of Liverpool are of this stone, which is in some places red, in some yellow, but in many localities white. At Stourton in Cheshire, at Grinsill near Shrewsbury, and at other large quarries, it is a thick-bedded white rock,

at Liverpool chiefly red, but often yellow and sometimes variegated. At Chester it is red, as the cathedral and ancient city walls conspicuously show.

There are sandstones in the Devonian and Silurian rocks quarried for building stones as the Old Red of Scotland and the Downton sandstone of Shropshire, but they are of less importance than the Carboniferous and Triassic stones.

A fine-grained pink sandstone of Permian age, from near Penrith, has recently been favoured by architects and used in London, in conjunction with white stone and brickwork, with pleasing effect.

The LIMESTONES suitable for building purposes are very numerous, including several that are so handsome when polished that they are used for internal decoration.

Portland Stone may perhaps be mentioned first amongst the limestones, as most of the large national buildings of London are of this material, as well as the majority of the minor stone edifices of the metropolis. The Portlandian, or Upper, Oolites having a considerable extension in the south of England, Portland Stone is by no means confined to the Isle of Portland. At Old Swindon and Chilmark in Wilts, and at Brill and Stone in Bucks, this well-known limestone is largely worked, though the quarries at Portland are the most extensive and the most famous. The Chilmark quarries supplied stone for Salisbury Cathedral and those at Portland gave to Sir Christopher Wren the material for St. Paul's. The beds worked for building stone are compact white politic limestones, but that called the "Roach Bed" is highly fossiliferous and vesicular. The "roach" has, however, been advantageously used in the construction of the great Breakwater at Portland.