6

Works which may be consulted.

Dana's System of Mineralogy;' Percy's Metallurgy;' Phillips's ‘Elements of Metallurgy;' Kerl's Metallurgy,' translated, with additions, by Crookes and Röhrig; Wagner's Chemical Technology;' Knapp's "Chemical Technology;' Ure's 'Dictionary of Arts and Manufactures;' Watt's 'Dictionary of Chemistry,'

XIX.

GENERAL SUMMARY.

HAVING described the relations that subsist between geology and the arts and manufactures, it may be of use to present a summary of the various mineral and metallic substances derived from the respective rock-systems. In this way the student will perceive at a glance, not only the lithological nature of the products obtained, but the comparative industrial importance of each production. It is true the lithology of the systems may differ in different localities; but generally speaking, there is considerable similarity over pretty wide areas, and the study of this summary may lead to a search for similar substances within the limits of the same formation. At all events, the outline will indicate, better than any lengthened description, the character and value of the products derived from the several systems, and in particular as developed in the British Islands.

POST-TERTIARY SYSTEM-SUPERFICIAL ACCUMULATIONS.

Silicious sands, for mortar, metal-moulding, glass-making, tempering of pottery and brick clays, and kindred purposes.

Shell-sands and shelly debris from sea-beaches, for agricultural purposes, and occasionally as a substitute for lime.

Gravels and shingle, for footpaths, roadways, filter-beds, and the manufacture of concretes and artificial stones.

Shore and drift flints (calcined and ground), for pottery admix

tures.

Clays of various kinds, for the manufacture of bricks, tiles, drainpipes, earthenware, porcelain, tobacco-pipes, and other fictile objects; for agricultural admixtures, &c.

Clays and river-muds of a calcareo-ferruginous character, for the manufacture of hydraulic cements.

Silicious silts and microphytal earths, for bath-bricks and other polishing preparations; for giving body and consistency, under the name of kiesel-ghur, to dynamite.

Shell and clay marls from lakes and old lake-sites, for agricultural purposes, top-dressings, and manurial admixtures.

Peat, for fuel and preparations of artificial fuels; charred for metal-smelting and for purification of sewage; occasionally distilled for its bituminous products, and often employed, both in the raw and charred state, as a manurial admixture.

Bogwood from peat-mosses and morasses, for ornamental purposes.

Bituminous exudatious, as naphtha, petroleum, and asphalt, largely and variously used in the arts and manufactures-lighting, cements, solvents, lubricants-and in medicine.

Ambrite from the soil of old forest-growths of the Damnara Australis in New Zealand.

Copal from the soil of old forest-growths of the Plæocarpus, &c., in Mexico and the Zanzibar coast of Africa.

Coral and coral-stone; some varieties for ornamental objects; others for building-stone and the preparation of lime.

Saline incrustations, and deposits of common salt, nitrates of soda and potash, borax, borate of lime, sal-ammoniac, &c, from brinesprings, salt-lakes, and salinas. Extensively and variously employed in the arts and manufactures, in medicine, and as top-dressings and stimulating manures.

Sulphur and sulphur-earths, found among volcanic ejections and in the mud discharged by solfataras. Largely used in the arts and manufactures-gunpowder, sulphuric acid, vulcanite, medicines, &c.

Guano, the desiccated and semi-mineralised droppings of seabirds, found on islets in rainless regions, as Peru, and prized as one of the most energetic of manures.

Bone-breccias and osite, cemented masses of bones found in fissures and caverns, and occasionally as islets (Sombrero) or old upraised bone-shoals; employed in the preparation of phosphatic

manures.

Metalliferous stream-drifts of sand and gravel, containing gold, platinum, tinstone, gems, and precious stones. Extensively dug, washed, and sifted in various regions for their gems and metallic

treasures.

Bog-iron ore, a recent deposit in bogs and marshes, occasionally employed as a commercial source of the metal, and in the purification of gas.

Titanic iron-sand, found along many shores, and sometimes collected as an ore of iron.

TERTIARY SYSTEM.

Silicious sands, for mortar, metal-moulding, glass-making, and similar purposes.

Flint gravels, for walks, roadways, concretes, porcelain admixtures, &c.

Clays of various qualities, for the manufacture of bricks, tiles, pipes, pottery, porcelain, and other fictile purposes.

Limestones of various origins and qualities, for mortar, agricultural and other purposes.

Septaria, or argillo-calcareous nodules from the clay-beds, for the manufacture of hydraulic cements.

Gypsums of various qualities, for the manufacture of plaster-ofParis, stuccoes, cements, and the like; also for agricultural topdressings and admixtures.

Phosphatic nodules, or coprolites, collected, cleaned, crushed, and used in the preparation of phosphatic manures.

Burrstones, or calcareo-silicious deposits, extensively employed in the construction of the finest and most durable millstones.

Lignites, or wood-coals, of various qualities, and abundantly developed in some tertiary areas, used for fuel, for gas-making, and occasionally for the distilling of bituminous products.

Amber, a gum-resin occurring in some lignitic beds, and used in the fabrication of ornamental articles, and occasionally in the preparation of varnishes.

Clay ironstone in nodular masses, as in the Bracklesham beds of the south of England.

Magnetic iron-sand and pisolitic iron-ore, occasionally used for the production of the metal.

CRETACEOUS SYSTEM.

Chalk, for quicklime, mortar, cement-making, furnace-flux, whiting, agriculture, and indeed for all the purposes of ordinary limestone; also for the cheap production of carbonic acid.

Compact limestones (often indurated chalks), for building, furnace-fluxes, cements, and agricultural uses.

Septaria, or argillo-calcareous nodules, for the manufacture of hydraulic cements.

Flints, for road-material, rustic walls, gun-flints, and for glazes and admixtures in the manufacture of glass and porcelain.

Fuller's earth, for fulling woollen fabrics, and for other detergent purposes.

Phosphatic nodules, for the preparation of artificial manures. Firestones, or soft refractory sandstones, for ovens, kilns, and smelting-furnaces.

Calcareous freestones, or ragstones, for local building purposes. Malm-rock, a soft silicious sandstone, containing a large percentage of soluble silica, and used for the procuring of this sub

stance.

Lignites and bituminous coals, occurring chiefly in foreign countries, as in the Western States of North America.

WEALDEN FORMATION.

Sands, for mortar, metal-moulding, and glass-making.
Clays, for the manufacture of bricks, tiles, and drain-pipes.

Sandstones and flagstones of fair quality, for building and paving purposes.

Ironstones (clay carbonate), in bands and nodules-at one time worked as an ore of iron.

Shelly marbles (Paludina, Sussex, and Petworth marble), at one time, and still occasionally, used for ornamental purposes.

Gypsum, of compact, white, and pure quality, discovered in the sub-Wealden boring of 1873-74.

OOLITIC FORMATION.

Oolitic limestones, or calcareous freestones, for building, decoration, mortar, agriculture, and allied uses.

Shelly freestones (Forest marble), occasionally used for ornamental purposes.

Lithographic limestone, extensively and variously employed in the art of lithography.

Flagstones and tilestones, for paving and roofing.

Fuller's earth, at one time very extensively, and still occasionally, employed in the fulling or deterging of woollens.

Bituminous shales, occasionally used, but with indifferent success, as fuels, and for the distillation of mineral oils.

Bituminous coals of various qualities (Yorkshire and Brora),— the most important coal - fields occurring in foreign countries (India, Indian Archipelago, Virginia, and perhaps China and Japan).

Ironstone (clay carbonate) of average quality- the English rarely exceeding 30 per cent of metallic iron.

LIAS FORMATION.

Blue clays of Lower Lias, dug along their outcrops, for brickmaking.

Aluminous and pyritous shales, for the preparation of alum and copperas, and occasionally for the extraction of sulphur and sulphuric acid.

Argillaceous limestones, for the manufacture of hydraulic mortars and cements.

Jet, chiefly for the manufacture of personal ornaments.

Ironstones (clay carbonates), in thick beds like those of Cleveland, and yielding from 28 to 33 per cent of metallic iron.

TRIASSIC SYSTEM.

Sandstones, often of indifferent quality, for building and flagging purposes.

Shelly limestones (muschelkalks), for mortar, agriculture, and other purposes of ordinary limestone.

Gypsum and alabaster, the former for the manufacture of plasterof-Paris, agriculture, &c.—the latter for ornamental purposes.