X=5^^ REESE LIBRARY OF THE . i UNIVERSITY OF CALIFORNIA. Class ECONOMIC GEOLOGY " THE EARTH is A GREAT STOREHOUSE OF WEALTH ; BUT IT REQUIRES KNOWLEDGE WHERE TO SEARCH, AND SKILL HOW TO SECURE IT." "THERE is NOTHING SUPERFLUOUS IN NATURE; NOTHING USELESS, IF MAN ONLY KNEW HOW TO TURN IT TO HIS ADVANTAGE." %& mstlVEBSITT '-- GRANITE QUARRY, DALBEATTIE (p. 134). ECONOMIC GEOLOGY OR GEOLOGY IN ITS RELATIONS TO THE ARTS AND MANUFACTURES BY DAVID PAGE, LL.D. F.G.S., &c. PROFESSOR OF GEOLOGY IN DURHAM UNIVERSITY COLLEGE OF PHYSICAL SCIENCE, NEWCASTLE-UPON-TYNE Author of Text-Books on Physical Geography and Geology ; 1 Handbook of Geological Terms ; ' ' Geology for General Readers,' Ac. &c. WILLIAM BLACKWOOD AND SONS EDINBURGH AND LONDON MDCCCLXXIV 1 fr 7 4 '-7 PREFACE. THERE are works on agricultural geology, on building and decorative stones, on mortars and cements, on coal-mining, on veins and lodes, and on ores and metallurgy ; but as far as the author knows there is no general treatise on geology in its numerous relations to the Arts and Manufactures. As a teacher in a busy centre of miscellaneous industry, he has experienced the want of such a work, and especially of one sufficiently brief and methodical to be used as a Text-book ; hence the origin of the present volume. While primarily intended for the student of Applied Geology, it may be useful to the agriculturist, builder, miner, civil engineer, manufactur- ing chemist, and others who have to deal with minerals and metals ; and at the same time may not be devoid of interest to the general reader. The field of industrial requirements is yearly extending, and there are few substances in the earth's crust which are now not turned to account in the multifarious industries of civilised life. A knowledge of these substances their nature, geolo- gical position, and abundance cannot fail to be of use to those who have to deal with them ; and some acquaintance with them, in a general way, can as little fail to be of inter- est to the intelligent observer of that scientific invention and industrial skill which labour so assiduously to convert every product of nature into objects of utility and ornament. It is impossible, within the limits of a single volume, to notice every substance and substances now lying waste and Vin PREFACE. worthless may, in a few months, be utilised, and become of importance ; but while not professing to notice every detail in Applied Geology, the author has endeavoured to present an intelligible outline of the subject, by grouping, under distinct heads, the various arts and manufactures in which mineral and metallic substances are employed. As it is chiefly with the raw materials their characters and modes of occurrence that the practical geologist has to deal, com- paratively little notice has been taken of the processes by which these are converted into the useful and ornamental. Such processes belong to technology, and come within the domain of the chemist, the metallurgist, and fabricator, requir- ing other knowledge and other lines of research than those that fall within the scope of the geologist. Where necessary, however, for the elucidation of the subject, the nature of these processes and appliances has been briefly indicated. Manipu- latory details must be sought for in technological treatises. Covering such a wide field, and condensing within the limits of a convenient Text-book, the author is sensible of imperfec- tions ; and would therefore solicit corrections and suggestions from those interested in the cause of education, and the pro- motion of needful and accurate knowledge. NEWCASTLE-ON-TYNE, October 1874. CONTENTS. I. INTRODUCTION, ' A i Aim and Object of Economic Geology. Illustrations of its Value and Importance. Acquisition of Geological Facts and Principles. II. THE ROCKY CRUST, . .8 1. ITS STRUCTURE AND COMPOSITION, . . 8 Stratified and Unstratified Rocks. Relative Positions of Rocks. Structure and Texture of Rocks. Hardness and Specific Gravity of Rocks. Composition of Rocks Chemical and Mineralogical. Mixed Rocks Classification and Description of. 2. CHRONOLOGICAL ARRANGEMENT OF ROCK - FORMA- TIONS, ..... 23 Methods of Determining their Relative Ages. Classification of Stratified Rocks. Classification of Unstratified Rocks. Use of Geological Maps and Sections. III. GEOLOGY AND AGRICULTURE, . . . 32 1. SOILS AND SUBSOILS, , . . . . 33 Soils of Disintegration. Soils of Transport. Fertile Admixture of Soils. Draining and Drainage. 2. MINERAL MANURES, .... 41 Carbonaceous Peat, Charcoal, Ashes, Soot, &c. Calcareous Marls, Chalk, Quicklime, Gypsum, &c. Saline Salts of Soda, Potash, Ammonia, &c. IV. GEOLOGY AND LAND-VALUATION, . . 50 1. SURFACE OR AGRICULTURAL VALUE, . 51 Modes of Estimating. The Landscape. Surface Amenity. 2. MINERAL OR GEOLOGICAL VALUE, . . 53 Modes of Determining. CONTENTS. V. GEOLOGY AND ARCHITECTURE PART I., 58 1. BUILDING-STONES, .... 59 Granites, Syenites, and Porphyries. Basalts, Greenstones, Felstones, &c. Slates, Schists, &c. Sandstones, Grits, Calcareous Freestones, &c. Limestones and Marbles. 2. 'STONES FOR DECORATION AND SCULPTURE, . 78 Granites, Porphyries, Syenites, Basalts. Slates and Serpentines. Limestones, Marbles, Alabasters. Rock-Crystal, Agates, Jaspers, Jade, &c. Malachites, Breccias, and Puddingstones. VI. GEOLOGY AND ARCHITECTURE PART II., 89 1. LIMES AND MORTARS, .... 89 Mortar Limestones, their Nature and Treatment. Hydraulic Limestones, their Nature and Treatment. 2. CEMENTS AND MASTICS, 95 Calcareous Water- Cements. Calcareous and other Oil- Cements. Bituminous Cements. 3. CONCRETES AND ARTIFICIAL STONES, . 98 Concretes for Foundations, Floors, Roadways, &c. Concretes for Building and Building-Blocks. Ransome's, Chance's, and other Artificial Stones. VII. GEOLOGY AND CIVIL ENGINEERING, . 105 1. ROAD-MAKING, . . .-"-.'. 106 Choice of Route and Gradients. Cuttings through different Rock-Formations. Embankments and Bridges. Materials for Highways, Streets, and Footpaths. 2. RAILWAY CONSTRUCTION, . . . in Choice of Route, Gradients, and Prospective Traffic. Cuttings and Tunnels through different Rock-For- mations. Embankments and Bridges. Water- Supply. 3. CONSTRUCTION OF CANALS, . v ,..,- . 115 Choice of Route, and Nature of Country. Cuttings and Tunnellings. Embankments and Aqueducts. Water- Supply Sites of Reservoirs. 4. CONSTRUCTION OF DOCKS AND HARBOURS, . 117 Choice of Site. Trial Borings and Excavations. Materials for Walls, Piers, and Breakwaters. 5. RIVER IMPROVEMENT, . . 119 Tidal Rivers Dredging and Deepening. Inland Streams Straightening and Embanking. CONTENTS. XI 6. WATER AND WATER-SUPPLY OF TOWNS, . 121 Springs and Surface-Wells. Deep Wells and Artesian Borings. Lakes and Reservoirs. Embankments, Tunnels, and Aqueducts. Waste Water Drains and Sewers. Till. GEOLOGY AND MINE ENGINEERING, . 130 1. QUARRYING OR OPEN-WORKING, . . 131 Stratified Quarries Modes of Working. Unstratified Quarries ,, 2. MINING IN STRATIFIED DEPOSITS, . . 136 Preliminary Surveys. Sinking or Shafting. Winning the Stratum Modes of. Obstacles and Obstructions to be overcome. 3. MINING IN VEINS, .... 145 Searching or Prospecting the Country. Working or Winning the Vein. General Phenomena of Metallic Veins. 4. STREAM OR PLACER WORKINGS, . . 151 Modes of Digging, Washing, and Sifting. Ij|. HEAT AND LIGHT PRODUCING MATERIALS, 156 1. FOSSIL FUELS, . . . . 156 Peat and Prepared Peat- Fuels. Lignites and Brown-Coals. Bituminous Coals Varieties of. Anthracites or Non-bituminous Coals. Petroleum, Crude Oils, Coal-Gas, &c. Artificial or Prepared Fuels. 2. LIGHT- PRODUCERS, . . . .169 Gas and Naphtha Springs. Petroleum Springs and Oil- Wells. Solid Bitumens Pitch, Asphalt, &c. Bituminous Shales Paraffin and Paraffin-Oils. Cannel-Coals Gas-Coals. X GEOLOGY AND THE FICTILE ARTS, . . 182 1. THE CLAYS WE FABRICATE, . . , 182 Kaolin, China, or Porcelain Clay. Pipe and Pottery Clays. Brick and Tile Clays. Fire-Clays, Terra Cottas. Infusorial Clays Floating Bricks. Meerschaum Plastic Magnesia. 2. THE SANDS WE VITRIFY, . . . 190 Glass and its Commercial Varieties. Materials employed in Glass-making. 3. GLAZES, ENAMELS, COLOURS, . . .192 Mineral and Metallic Bases of these. xii CONTENTS. XI. GRINDING, WHETTING, & POLISHING MATERIALS, 195 1. MILLSTONES, . ... . . 196 Sandstones, Gritstones, and Quartzites. Burrstones, Lavas, &c. 2. GRINDSTONES AND CUTTING WHEELS, 197 Sandstones and Grits. Solid (prepared) Emery Wheels. 3. CRUSHING AND PULPING WHEELS, . . 199 Sandstones and Grits. Quartzites, Granites, Lavas. 4. POLISHING AND CUTTING MATERIALS, . 199 Quartz- Sands Crushed Sandstones. Tripoli, Rotten-Stone, Bath-Brick, Polishing Pastes. Pumice, Emery, Garnet-Rock. Diamond-Dust^ and Diamond-Points. 5. WHETSTONES AND HONES, . . . 204 Batts or Silicious Sandstones. Hones and Oilstones. 6. BURNISHERS, ..... 2 o6 Agates, Bloodstones, Carnelians, Jaspers, &c. XII. REFRACTORY OR FIRE-RESISTING SUBSTANCES, 208 1. ARTIFICIAL PREPARATIONS, . . . 2 o8 Fire-Clay and Fire-Clay Manufactures. Infusorial Earths and Clay Admixtures. Graphite and Clay Admixtures. 2. NATURAL PRODUCTS, . . . . 213 Firestones or Quartzose Sandstones. Leckstones or Porous Trap-Tuffs. Potstone or Steatite. Asbestos. XIII. PIGMENTS, DYES, AND DETERGENTS, . 217 1. PIGMENTS, ...... 2I 7 Mineral Pigments from Earths and Ochres. Metallic Pigments prepared from Metals. Pastel Pigments, Coloured Pastes of Earths and Ochres. 2. DYES, . . . . . 223 Prepared from Minerals and Metallic Salts. 3. DETERGENTS, ;, '; . . '.; l . 223 Native or Mineral, as Fuller's Earth. Artificial or Chemically prepared. XIV. SALTS AND SALINE EARTHS, . . 226 i. SALTS OF SODA, . . . 226 Chlorides Rock-Salt, Bay-Salt. Carbonates Natron, Trona, &c. Nitrates Nitratine. Sulphates Glauber-Salt, Glauberite. Borates Borax. Fluorides Cryolite. CONTENTS. Xlll 2. SALTS OF POTASH, . . . .231 Nitrates Nitre, Saltpetre. 3. SALTS OF MAGNESIA, .... 232 Sulphates Epsom Salts, Epsomite. 4. SALTS OF AMMONIA, .... 233 Muriates Sal- Ammoniac. Carbonate of Ammonia. Sulphate of Ammonia. 5. SALTS OF ALUMINA, . . . . 233 Alum-Shales, Alum-Slates, Alum-Stone. Potash- Alum, Soda- Alum, Ammonia-Alum, &c. 6. METALLIC SALTS, .... 235 Sulphate of Iron, Copperas, Green Vitriol. Sulphate of Copper, Cyanose, Blue ,, Sulphate of Zinc, Goslarite, White ,, 7. BARYTES STRONTIA, .... 236 Carbonates and Sulphates of. 8. SULPHUR, SULPHUR EARTHS AND ORES, . 237 Sulphur, native and prepared. XV. MINERAL AND THERMAL SPRINGS, . . 240 THEIR NATURE, ORIGIN, AND CLASSIFICATION, . 240 Indifferent Springs. Earthy ,, Sulphur ,, Saline Alkaline Purgative Chalybeate Bituminous Mud XVI. MINERAL MEDICINES, .... 259 Arranged in alphabetical order, according to the earths and metals from which they are prepared. XVII. GEMS AND PRECIOUS STONES, . . 263 1. THE CARBON GROUP, . . . 264 Diamond, Bort, Carbonado. Amber, Ambrite. Jet, Bogwood, Cannel-Coal. 2. THE ALUMINA GROUP, . . . 268 Corundum. Ruby. Sapphire. Turquoise, Odontolite. 3. THE SILICA-ALUMINA GROUP, . .271 Topaz. Emerald, Beryl. Lapis Lazuli. Moonstone, Labradorite. Garnets, Pyrope, Almandine, Carbuncle. XIV CONTENTS. 4. THE SILICA GROUP, . -. '*.. . Rock-Crystal, Amethyst, Cairngorm, &c. Calcedony, Agate, Carnelian, Onyx, &c. Opal. Jasper, Jade, Menilite, &c. 5. MISCELLANEOUS GROUP, Malachite. 6. PASTES OR ARTIFICIAL GEMS, . 275 279 280 XVIII. THE METALS AND METALLIC ORES, . . 283 1. THE NATIVE METALS, .... 284 Gold. Platinum. Palladium. Silver. Mercury, Copper, Iron, Arsenic, Antimony, &c. 2. THE METALLIC ORES, .... 288 The metals in alphabetical order, with notices of their physical properties, principal ores, and applications in the arts and manufac- tures. XIX. GENERAL SUMMARY, 321 Post-Tertiary System and its Industrial Products. Tertiary System Cretaceous System Wealden Formation Oolitic Formation Liassic Formation Triassic System Permian System Carboniferous System Old Red and Devonian and their Silurian and Cambrian ,, Laurentian and Metamorphic Volcanic Rocks ,, Trappean Rocks t ? Granitic Rocks INDEX, ILLUSTRATIONS. GEOLOGICAL MAP OF THE BRITISH ISLANDS (In pocket.) GRANITE QUARRY, DALBEATTIE (Vignette.) EDINBURGH CASTLE ROCK ERUPTIVE AND STRATIFIED MASSES, ....... 9 DYKES, FAULTS, VEINS, ..... 10 CUTTING THROUGH BOULDER-CLAY, . . . .112 ARTESIAN WELLS IN SYNCLINAL STRATA, . . .124 DYKE AND DEEP- WELL BORINGS, . . . .126 BENCH OR STAGE WORKING, . . . . .132 POST-AND- STALL WORK, . . . . 139 LONG- WALL WORK, ...... 140 WASH-OUT, NIPS-OUT, NATURAL PITS, . . . 143 DYKE -FAULT, STEP -FAULTS, THROUGH -FAULT, REVERSED FAULT,' ....... 144 VARIOUS VEINS, ....... 146 FAULTED OR DISPLACED VEINS, .... 147 VEIN-MININGSHAFTS AND ADITS, . . . .149 HYDRAULIC PLACER-WORKING, . . . . 153 AMERICAN OIL-WELL (after Gesner), . ' . . . 173 BURRSTONE MILLSTONES, ' . . . . 197 GEM-GUTTINGROSE, BRILLIANT, EN CABOCHON, . . 265 ECONOMIC GEOLOGY. I. INTRODUCTION. THE study of Geology presents itself in two__great aspects one purely scientific^ and- appealing to the intellect; another mainly practical, and appealing to the industrial necessities of .life. ., In its scientific aim it examines, maps out, and arranges the rocks of the earth's crust into formations and life-systems according to their composition, relative positions, and fossil contents ; endeavouring to deduce therefrom a connected his- tory of our globe and its successive aspects from the earliest to the most recent times. In its practical effort it takes advantage of this chronological arrangement of rock-formations, and en- deavours to discover in each those minerals and metals their quality, quantity, and accessibility which bear so directly on the arts and industries of civilised existence. Though thus apparently separate, the scientific and the practical cannot in reality be disjoined. The more exact our knowledge of the position and sequence of rock -formations, the more certain our economic explorations become ; and the more successful our industrial adventures, the greater will be the impetus given to the extension and exactitude of scientific research. There can, indeed, be no antagonism between science and art, between theoretical knowledge and its economic applications. The practical expression of a truth can never be divorced from its theoretic conception. Apart from its utilities, Geology will ever be a theme of intellectual interest and research, the problems of time, change, and progression it involves being amongst the most attractive that can engage the educated mind. It is equally true, how- 2 INTRODUCTION. ever, that the science is pregnant with practical value, and will ever be so, so long as man has to draw from the earth the ma- terials for the fabrication of his tools and machinery, for his heating and lighting, and for the construction of his dwellings and their adornment. Though appealing more directly to the agriculturist, the land valuator, the architect, the civil engineer, the mining engineer, and the manufacturing chemist, this prac- tical aspect of Geology is of universal importance. Man cannot make progress in civilisation without drawing from the mineral and metallic stores of the earth's crust. He may lead a savage or a nomadic life, and subsist on roots and fruits, by hunting, by fishing, or on the produce of his herds and flocks ; but he cannot settle down in civilised communities, or combat success- fully with the forces of nature, till he has learned to arm himself with tools and implements. Personally he is weak weaker than many of his fellow-creatures; and it is not till he has furnished himself with implements and these, the best of them, drawn from the earth that he can till the soil, reap his harvests, hew the wood, fashion the stone, or reduce the ore. And the more numerous his civilised wants become, the more he draws from the earth rearing his cities, decorating his mansions, erecting bridges, piers, and harbours, creating new sources of heat and light, fabricating machinery, laying railways, building steam-ships, and stretching telegraphic cables, the raw materials of which he obtains, and obtains alone, from the rocky crust. In this way a knowledge of the composition and structure of the earth becomes more and more indispensable ; hence an acquaintance with Geology, if he would learn where this or that mineral is to be found, the abundance in which it occurs, and the facilities with which it can be obtained. The minerals and metals are not scattered broadcast through the earth. Were coal, copper, and iron, for example, of universal dis- semination, man would have only to dig and mine ; but each has its own place and mode of occurrence, and to determine these, to map and describe them for the information of others, is the function of the geological surveyor. Whoever, therefore, has to deal with the products of the earth in their economic or commercial aspects, cannot fail to be benefited by some scant- ling of geological knowledge, were it only to enable him to read with appreciation the discoveries and descriptions of others. Let us endeavour to make this clearer by a few illustrative examples. And first, the soils we cultivate depend for their fertility on their composition and texture. This composition and texture may be naturally unfertile, and yet may be capable of improve- INTRODUCTION. 3 ment by simple admixture of other soils, by drainage, or by mineral manuring. The agriculturist who knows the nature of his soils and subsoils, and of their underlying rocks, is surely, therefore, in a better position to correct their deficiencies by admixture, by draining, and by manuring, than one who cannot discriminate the nature of these soils or detect their deficiencies. The elements of fertile admixture may lie within the same farm ; the defects in composition may be corrected by the applica- tion of appropriate mineral manures ; but how can the farmer obtain this needed information save through a geological ac- quaintance with the nature of the materials he has to operate upon and apply? " Let him obtain it from the geologist," say some, "and apply it empirically." So far good ; but infinitely better that the agriculturist knew something of the matter him- self, and could separate the wheat from the chaif of his scien- tific advisers. There is no mystery in the relations of soils and subsoils, in their composition, or in their texture nothing which a man of average intelligence may not readily master without going deeply either into the study of theoretical geology or into the manipulations of chemical analysis. Secondly, as the worth of an estate depends not only on its agricultural, but also on its mineral value, the land valuator who is unable to determine the character of its soils and subsoils, and is ignorant of ibs mineral structure, can never do justice to his client. A knowledge of the geo- logical structure of an estate is not less necessary to fixing its real value than a knowledge of its various soils and climate, and it is often for want of this knowledge that estates are either sold under their value or bought at unre- munerative prices. At the present day, when farm produce meets so ready a market, and the minerals and metals bring such high prices, no estate should be bought or sold without a thorough survey alike of its surface capabilities and of its mineral stores, and this cannot be done with any degree of satisfaction without appealing to the mineral surveyor as well as to the mere agriculturist. No estate agent is worthy of the name who is incapable of appreciating this twofold aspect of the value of landed property. Again, take the case of the architect who has to deal with beauty and durability of structure without, and with elegance of decoration within. The beauty and durability of a building- stone, and the facility with which it can be obtained and dressed, is of prime importance in architecture. The stone which will keep its colour in the open country may not do so in the smoky city ; and the rock which will resist the action of 4 INTRODUCTION. the weather in its normal state may waste and crumble under the carbonated atmosphere of the manufacturing town. Nor is it structure and decoration alone that call for the assistance or suggestions of the geologist. The mortars, the cements, and concretes of the builder are yearly assuming a greater im- portance and receiving a wider application ; and as the com- ponent materials of these are all drawn directly from the earth, geology comes in with important information to the manufac- turer indicating the nature and abundance of the limestones, and sands, and gravels with which he has to operate. It is ignorance on this point which often causes the builder to bring from a distance materials which could be obtained of equal quality and at a cheaper rate in his own immediate locality. It is also a want of knowledge on this head that permits the artificial manufacture of hydraulic cements and concretes, while limestones of natural hydraulic energy lie unknown and ne- glected. In the next place, take the case of the civil engineer who has to plan and lay down roads and railways, to execute cuttings and tunnels, to excavate docks and harbours, to erect piers and breakwaters, to deepen and widen tidal rivers, and bring in water-supplies to towns. Not a step can be taken in any of these important operations without coming in contact with geological phenomena not a plan can he lay down which does not depend more or less on a knowledge of rocks and rock-formations. It is true he may obtain information from geological maps and from professional geologists ; but, even with this aid, his work will be executed with feebleness and uncertainty compared with that of one who can discriminate the geological structure of a country for himself. And it has simply been, and still is, for want of this geological knowledge that so many of our engineering works have been executed at so much cost and with so little pecuniary satisfaction to their proprietors. Once more, and we come to the mining engineer whether working among stratified rocks for such products as coal, iron- stone, limestone, and fireclay, or following veins and lodes in search of the metals and metallic ores. In either case some knowledge of geology is indispensable ; and though it is true that mining was largely followed ere geology had shaped itself into a science, yet the practical skill of the miner in dealing with successions of beds, with dykes and dislocations, and with kindred phenomena, is geology of a kind, requiring the noting of facts and the drawing of generalisations, not less real and serviceable than the deductions of the theoretical geologist. INTRODUCTION. 5 The wider, however, the geological knowledge of the mining engineer, the better will he be able to cope with the difficulties that present themselves in his arduous calling. His services may not always be restricted to the same district. His advice may be sought in other districts, where there are other rocks, other successions, other dislocations and appearances, and he will be but poorly prepared to deal with these unless he is in some measure acquainted with the general principles of geology. Besides, new substances are yearly being utilised, and it is the duty of the mining engineer to keep pace with this progress, and to see that nothing in his workings be left unnoticed or unused. While every region of the globe is being ransacked to supply the mineral and metallic requirements of Europe and America, the mining engineer may safely calculate upon a wider field for his services and these services can only be valuable and reliable in proportion to his scientific knowledge of the subjects with which he has to deal. Sinking shafts, driving drifts, pumping, and ventilation, are arts of prime im- portance ; but where to sink, the nature of the minerals sought, their mode of occurrence, and the dislocations to which they may have been subjected, are of equal importance, and can only be known through some acquaintance with the science of geology. But it is not alone to the farmer, the land agent, the builder, the civil engineer, or the mining engineer, that some acquaint- ance with geology is of importance. Its applications to the arts and manufactures are numerous and direct to the fictile arts of the potter and glassmaker, to the manufacturer of mineral pigments and dyes, to the metallurgist and chemist, to the lapidary and jeweller, and even to the mechanical engineer and machinist. The potter and glassmaker derive all their clays and sands from the earth ; all our mineral pigments are procured directly or indirectly from the same source ; so like- wise are all our metals, whether native or as ores ; and so also our fossil fuels and lights ; our millstones, grindstones, and whetstones ; our salts and saline earths ; our gems and precious stones. In fine, there are few of the arts and manufactures which do not less or more depend on the mineral and metallic treasures of the earth ; and surely some acquaintance with the composition and structure of that earth, so that the place of those minerals and metals may be known, their abundance ascertained, and the facility of obtaining them be determined, cannot fail to be of advantage to those who have to fashion and fabricate them into objects whether of utility or ornament. It is not required of practical men to go deeply into the 6 INTRODUCTION. theories of geology, for that is impossible, and useless even if it were possible ; but surely an intelligent acquaintance with the nature and origin of the materials they are daily manipulating cannot be otherwise than a gain, and a source of satisfaction even where the thought of pecuniary gain is altogether out of the question. Civilisation depends in a prime degree upon our mastery over the opposing forces of nature, and we cannot conquer any force or power save by the application of a superior one. Physically, man is weak and helpless ; armed with implements and machinery he becomes a Titan. Without tools and machinery, man has to succumb to the forces of nature ; equipped with these, they become his willing servants turning his wheels, raising his weights, wielding his hammers, lessening his labours, and carrying him over land and sea with unparalleled celerity. Our most important implements and machinery are derived from the mineral world ; the heat that sets them in motion is derived from the same exuberant source. How direct, then, our civilised dependence upon the earth and a knowledge of its mineral and metallic treasures ! How im- portant to every art and manufacture to learn something of the nature and character of the source from which they are pro- cured ! To obtain this information, in a general way, is by no means a difficult task. It is not required of the practical operator that he should be learned in geological theories, in mineral species, or in palseontological discriminations. Enough for his purpose to understand the chronological succession of the rock-formations, to know the general character of the strata of which they are respectively composed, the changes these strata may have undergone, the areas over which they are spread, and the facilities with which any of their products can be obtained. The study of any recent text-book, the power to read aright geological maps and sections, and a knowledge of the composi- tion of the peculiar products he has to deal with, are about all he requires for the prosecution of his task. Armed with this amount of knowledge, he will be enabled to conduct his opera- tions with greater certainty, and be less liable to be led into visionary speculations and experiments. Acquainted with the wide and varied field of geological products, he will cease to abide by local and restricted supplies, while cheaper and more easily manipulated substances can be obtained from other regions. To put the facts of Economic or Applied Geology plainly and methodically before the reader is the aim of the present treatise ; and though each department may be studied separ- INTRODUCTION. 7 ately, a better knowledge of the subject will be gained by going over the whole, and especially by carefully reading the introduc- tory chapters devoted to the general principles and classifications of the science. Understanding the chronological arrangement of the systems, and the general lithological character of the various formations, the practical operator will be in a much better position to understand the nature of the materials that come within the range of his own special department. Of course, it is only with the raw materials their nature, posi- tion, and abundance that the practical geologist has to deal. The moment they pass to the furnace, the retort, or the fac- tory, they come under the domain of the metallurgist, the chemist, and fabricator, whose processes and appliances re- quire other knowledge and other lines of research. It is true the geologist cannot be altogether indifferent to these pro- cesses and appliances ; but, at the same time, it must be re- membered that his special function is to discover the raw materials, to determine their positions and accompaniments, their abundance, and the facilities with which they may be procured; and generally, to arrange and classify them be they mineral or metallic so as to know their variety, their rarity, or their exuberance in the crust of the earth. Restricting himself to this function, the geologist can supply much valuable information, and this without at all infringing on the field of the technologist, whose methods are mainly of a chemical and mechanical nature. II. THE ROCKY CRUST. I. ITS STRUCTURE AND COMPOSITION. ALL the minerals and metals with which the arts and manu- factures have to deal being obtained from the earth's crust, some knowledge of its structure and composition is indispen- sable to the economic geologist. For this reason we devote the present chapter to a brief outline of Geology; more especially as regards the physical characters of rocks and minerals, their modes of occurrence, and their chronological arrangement. With due attention any intelligent reader may easily make himself acquainted with these peculiarities ; and the more intimate his knowledge, the better will he be enabled to understand the nature of the industrial products and pro- cesses that may come under review. Stratified and Unstratified Rocks. The exterior crust, which forms the theme of the geologist, is composed of rocks ; and under this term are included all its substances, whether hard or soft, superficial or deep-seated sands, sandstones, clays, shales, peats, coals, limestones, ironstones, lavas, basalts, granites. Whatever their mineral character, these rocks are found to occur in two main positions stratified or bedded, and unstratified or eruptive. Reason- ing from the manner in which rock-matter is deposited at the present day in lakes, estuaries, and seas, the stratified are re- garded as of sedimentary or aqueous origin that is, as having been formed through and by the agency of water. And rea- soning, in like manner, from the ejectments of volcanoes, the unstratified are regarded as of eruptive or igneous origin that is, as having been formed through and by the agency of fire. In the accompanying illustration, the " Castle Rock " of Edinburgh is a truly eruptive or unstratified mass breaking through the sedimentary or stratified sandstones and shales THE ROCKY CRUST : ITS STRUCTURE. 9 which are tilted up, and slope away from the centre of erup- tion. Wind-blown materials, as sand-dunes chemical de- posits, as calcareous tufa and organic growths, like peat-moss and shell-beds are usually classed with the stratified ; while showers of volcanic ashes, and other irregular ejectments, though arranged more or less in layers, are described merely as stratiform. Generally speaking, the sedimentary rocks are formed from the waste and debris of pre-existing rocks, are lam- Edinburgh Castle Rock : Basaltic Clinkstone passing through Lower Carboniferous Shales and Sandstones. inated or bedded in structure, comparatively soft and fragment- ary in texture, and frequently imbed the remains of plants and animals. The eruptive rocks, on the other hand, however originating, make their appearance from below, are amor- phous, or occasionally columnar, in structure, uniform and crystalline in texture, and rarely imbed any traces of organic remains. While the preceding are the general characteristics of the stratified and unstratified rocks, it must be borne in mind that there are many anomalous masses of conglomerate and breccia on the one hand, and curious sheet-like overflows and stratiform ash-beds on the other. At the present day, stratified rocks are being laid down in all lakes, estuaries, and seas, and unstratified ejected from all volcanic centres. And as the forces (meteoric, aqueous, or- ganic, chemical, and igneous) by which old rocks are wasted and new ones reconstructed from their debris, are as enduring as the planetary system from which they take their rise, the geologist is entitled to ascribe the formation of the rocky crust to the operation of similar agencies in former periods. In this 10 THE ROCKY CRUST: way, land and water are gradually but continually changing places the rock-matter formed during each terraqueous change being not only the record of these mutations, but an indication of the physical aspects of our globe at the succes- sive stages of its history. Relative Positions of Rocks. Laid down in water and assorted by water, the original position of the stratified rocks is that of horizontality ; but having been subsequently acted upon by the vulcanic or erup- tive forces, they usually occur, as may be seen in our sea-cliffs, ravines, and railway cuttings, in inclined, bent, and contorted positions, and more or less rent and fissured some portions being thrown up and others thrown down, or, in technical language, faulted and dislocated. These rents and fissures are occasionally filled up with rubbly matter washed in from above, and sometimes with molten matter injected from below ; and hence the occurrence of dykes, as they are termed " soft " in a Simple fissure ; b. Fault ; c Soft dyke ; d Hard dyke ; -w Veins. the former instance, and " hard " in the latter intersecting and interrupting the continuity of the sedimentary strata. Again, when these rents and fissures have been filled up by slow in- filtration of mineral and metallic matter, they constitute veins and lodes the veinstone or matrix consisting of calc-spar, fluor-spar, quartz, baryta, or other sparry material, while the accompanying metallic ores are in the state of oxides, sul- phides, carbonates, and other chemical combinations. The slope at which a stratum lies to the horizon constitutes, in geo- logical language, its dip or angle of inclination ; that portion of a stratum which comes to the surface its outcrop or basset-edge ; and a line at right angles to the dip its strike or stretch across the country this strike being always at right angles to the dip, and vice versa. Melted and erupted by vulcanic heat from below, the igne- ITS STRUCTURE AND COMPOSITION. II ous rocks, on the other hand, occur as unstratified or amor- phous masses, and as regards their relations to the strata through which they pass are spoken of as disrupting, or breaking through; overlying, having flowed over; inter stratified, having flowed over and been subsequently covered by other sediments ; and intrusive, when thrusting themselves, as it were, with some degree of parallelism, among and between the sedimentary beds. Structure and Texture of Rocks. The manner in which rocks are arranged or piled up in the crust constitutes their structure; and this structure is described by such terms as stratified, bedded, jointed, tabular, columnar, massive, amorphous, &c. The internal arrangement of their particles constitutes their texture, and this, as the case may be, is spoken of as earthy, granular, crystalline, fibrous, porous, compact, vitreous, &c. The columnar aspect of the basalt of the Giant's Causeway is its structure ; a chip from any of the columns exhibits its internal crystalline texture. The outward portion of a rock, exposed to and acted upon by the atmo- sphere, is spoken of as its weathered surface ; and the internal texture, laid open by the hammer, as its fresh-fracture. The fresh-fracture of a rock may give no indication how it will be affected by exposure to the weather ; the weathered surface, on the other hand, exhibits faithfully the effect of meteoric agency in discolouring and disintegrating, and is consequently of great use to the builder and architect. The fracture of rocks depends on their texture, and is described as even, flat, bladed, hackly or irregular, splintery, conchoidal and sub- conchoidal, according to the appearance it presents. Roof- ing-slate, for example, splits up with a flat or regular surface, calcareous spar cleaves with an even or smooth face, while a piece of flint or cannel-coal breaks up with a conchoidal or shell-like fracture. A knowledge of the manner in which a rock breaks and cleaves is often of great use, not only in faci- litating the operations of the quarryman and mason, but in preventing unnecessary waste of the material. A workman quarrier, paviour, or mason acquainted with the structure and texture of rocks, will not only turn out a larger amount of material with the same labour, but will, by his skilful mani- pulation, effect a saving of the material itself. Hardness and Specific Gravity of Rocks. The specific gravity of rocks is determined by the standard of distilled water at 60, which is regarded as i ; and their 12 THE ROCKY CRUST: relative hardness is determined by the following scale, invented by the German mineralogist Mohs : Talc, . Gypsum, . Calc-spar, . Fluor-spar, Apatite, Felspar, Rock-crystal, Topaz, Corundum, Diamond, . Thus, common haematite, or red oxide of iron G = 4.5 - 5.5 ; H = 5.5 - 6.5 means that its specific weight is from four and a half to five and a half times greater than that of water, and that in hardness it stands between five and a half and six and a half in the above scale. The determination of specific gravities is often a delicate and difficult operation ; but the relative hardness of rocks and minerals is readily approxi- mated. Thus, if a mineral scratches felspar, but is in turn scratched by rock-crystal, its hardness must be between 6 and 7, and may be indicated as 6.4 or 6.8, according as it seems to approach the felspar on the one hand, or the rock-crystal on the other. A knowledge of the relative hardness of rocks and minerals is often of essential importance in the arts and manufactures, and hence the value of their determination in practical Geology. The following table of Specific Gravities may also be of use for future reference : Agate, . . 2.590 Glass, green, . ,, flint, . 2.642 2.760 to 3.000 Amber, . . .. Amethyst, Common, , , Oriental, Amianthus, Arragonite, .' Asphalt, Azure-stone, . Baryjtes, Sulphate of, ,, Carbonate of, Basalt, . Beryl, . '.. -.'" 1.064 to i. loo . 2.750 . 3-391 0.315 to i. ooo . 2.900 0.905 tO I.22O . 2.850 4-550 . 4.600 2.421 to 3.000 3-549 Granite, Graphite, Gypsum, Compact, , , Crystallised, Heliotrope, Honeystone, Mellite, Hornblende, . Hornstone, Hyacinth, . . Ironstone, Jasper, . Jet, s . . 2.660 to 2.800 1.987 , 2.400 1.870 , 2.288 2.311 , 2.900 2.629 3-000 . 1.650 3.250103.830 2.555 . 2 - 8j O 4.000 , 4.780 3.000 , 3.575 2.358 , 2.820 Calcedony, .. ': . \ . 2.600 to 2.650 Limestone, Magnesia, Carbonate, 2.386 to 3.000 . 2. 240 Chalk, . Chrysolite, .. . Coals, . . i Coral, . Corundum, Diamond, Oriental, 2. 000 tO 2.255 , , . 3-400 1.025 to 1.350 2.500 ,, 2.800 . 3-710 q. C2I Malachite, Marble, . Melanite, METALS Antimony, . 3.572 to 3.994 2.500 ,, 2.700 3.600 ,,3.800 . ^- . 6.702 , , Coloured q.cco . . 9.880 , , Brazilian Dolomite, . 3.444 2.540 to 2.830 Brass, . 7.809 to 8.400 . 8.600 Emerald, Felspar . 2.600 ,, 2.770 2 4.^0 2 7OO Chromium, i Cobalt . 5.900 . 8.600 Galena, . Glass, crown, . 6.565 7-786 . 2. S20 Columbium, Copper, . 5.600 . 8.900 ITS STRUCTURE AND COMPOSITION. , , hammered, . iy.^>o . 19.361 Obsidian, .... 2.370 Oolite, . . . 2. 100 to 2. 600 Opal, . . . 1.0^8 .. 2. no Iron, cast, . 7- 2 48 . 7.788 Pearlstone, Pitchstone, Porphyry, Pumice, . Quartz, . Rock-crystal, Ruby, Oriental, Sandstone, Craigleil Fife, . , . Glasgow ,, Derbysh ,, Newcas Sapphire, Oriental, Schorl, . Serpentine, Slate, . Spar, Fluor, ,, Calc, Sulphur, nativ , fused . 2.340 2.000 tO 2.700 2.450 ,, 2.950 0.752 ,, 0.914 2.624 ,, 3.750 2.580 ,, 2.888 4.285 h, 2.350 2.100 r, 2. 156 ire, 2.628 tie, 2.229 4.200 2.922 to 3.450 2.264 ,, 3.000 2.000 ,, 2.000 3.000 ,, 3.790 2.510 ,, 2.800 3-033 Lead . Manganese, Mercury, Molybdenum, . 8.000 . 13.598 . 8.600 . 8.279 ,, forged, . Osmium -iridium, Palladium, . Platina, forged, . ,, wire, plate, . Potassium, . 8.666 . 19-500 . 11.800 . 20.336 . 21.042 . 22.069 . 0.865 Selenium, . Silver, hammered, Sodium, Steel, soft, . tempered, . Tellurium, . Tin, . Tungstein, . Uranium, . Zinc, . Mica, . Mineral Tallow Naphtha, . 4.300 . 10.474 . 10.510 . 0.972 7.833 . 7.825 5.700 to 6. 1 10 . 7.295 . 17.400 . 9.000 6.200 to 7.200 2.650 2.934 . 0.780 0.700 to 0.840 Talc, Topaz, . Tourmaline, Turquoise, Ultramarine, Woodstone, Zeolite, . Zircon, . 2.000 tO 3-000 4.000 ,, 4.066 3-000 ,, 3.680 2.500 ,, 3-000 2.360 2.000 tO 2.674 2.075 2.718 4.385 ,, 4.700 Composition of Rocks. But whether occurring as stratified or unstratified masses ; whether horizontal, inclined, bent, or contorted ; whether in dykes, veins, or lodes ; whether bedded, tabular, or columnar in structure, or earthy, granular, or crystalline in texture, all rocks may be viewed as having a certain mineral and chemi- cal composition. By this mineral composition is understood the mineral particles of which they are composed, as a quartzose sandstone chiefly of quartz grains, or as an ordinary granite of the minerals quartz, felspar, and mica. By their chemical composition, on the other hand, is meant the ultimate elements of which their various minerals are composed quartz, consisting of oxygen and silicon, felspar of oxygen, silicon, alu- minium, sodium, potassium, &c., and mica of oxygen, mag- nesium, potassium, &c. Simple minerals, which constitute the study of the mineralogist, have usually a definite crystalline form and chemical composition; but the great bulk of the earth's crust, which constitutes the theme of the geologist, consists of mixed rocks, having no definite form or composition, and made up of several mineral ingredients. The simple 4 THE ROCKY CRUST: minerals are very numerous, as quartz, felspar, mica, horn- blende, augite, calc-spar, &c.; the mixed rocks also occur in many kinds, as granites, porphyries, basalts, greenstones, sand- stones, limestones, &c. ; while the known chemical elements amount to sixty-five or sixty-six, some being metallic, as gold, silver, lead some non-metallic solids and liquids, as sulphur, carbon, silicon, iodine and others gaseous or aeriform, as oxy- gen, hydrogen, nitrogen. The following Tabulations of Chemical Elements, Mineral Species, and Mixed Rocks, will be useful at this stage, as showing the nature and extent of the field with which the ge- ologist has to deal ; while they will be required for frequent reference when we come to treat of many of the products em- ployed in the arts and manufactures. CHEMICAL ELEMENTS. The following list exhibits, in alphabetical order, the so- called " elementary substances," with the symbols by which they are known in mineral composition and analyses thus, carbonate of lime, Ca O + CO 2 or Ca C. Elements. Symbols. Elements. Symbols. Aluminium, . Al Nickel, Ni Antimony (Stibium Sb Niobium, Nb Arsenic, As Nitrogen, . N Barium, Ba Norium, No Bismuth, Bi Osmium, Os Boron, B Oxygen, Bromine, Br Palladium, . Pd Cadmium, . Cd Pelopium, . . Pe Caesium, Cs Phosphorus, P Calcium, Ca Platinum, Pt Carbon, C Potassium (Kalium), K Cerium, Ce Rhodium, . R Chlorine, . , Cl Ruthenium, . Ru Chromium, . Cr Selenium, . Se Cobalt, Co Silicium, Silicon, . Si Copper (Cuprum}, Didymium,. Cu Silver (Argentum), . Sodium (Natrium), Ag Na Erbium, . ^ Strontium, . Sr Fluorine, F Sulphur, S Glucinium or Beryll urn, Gl Tantalum or Columbium, Ta Gold (Aurum), Au Tellurium, . Te Hydrogen, . H Terbium, Ilmenium, . 11 Thallium, . Ti Iodine, I Thorium, Th Iridium, Ir Tin (Stannum), Sn Iron (Ferrum), Fe Titanium, . . - Ti Lanthanum, Lead (Plumbum), Ln Pb Tungsten or Wolfram, Uranium, W U Lithium, Li Vanadium, . ' .#? V Magnesium, Mg Yttrium, . . y; Y Manganese, Mn Zinc, . . Zn Mercury (Hydrargyrum], Hg Zirconium, . Zr Molybdenum, Mo ITS STRUCTURE AND COMPOSITION. 15 Of the preceding elementary substances only a few enter largely into the composition of the earth's crust ; and of the others many are extremely rare, or only evolved from their natural unions by chemical analysis. In the following list the most important (geologically speaking) are printed in capitals, their characters being given as under the ordinary pressure and temperature of the atmosphere : Gases HYDROGEN, OXYGEN, nitrogen, CHLORINE, and FLUORINE. Non-Metallic Liquids and Solids Bromine, iodine, SULPHUR, PHOS- PHORUS, selenium, CARBON, boron, SILICON. Metals being the basis of the Earths and Alkalies POTASSIUM, SODIUM, lithium ; BARIUM, strontium, CALCIUM ; MAGNESIUM, ALUMINIUM, thorium, glucinium, zirconium, yttrium. The Metals MANGANESE, ZINC, IRON, TIN, cadmium, COBALT, NICKEL ; ARSENIC, CHROMIUM, vanadium, molybdenum, tungsten, colum- bium, ANTIMONY, uranium, cerium, BISMUTH, titanium, tellurium, COPPER, LEAD J MERCURY, SILVER, GOLD, PLATINUM, palladium, rhodium, osmium, iridium, ruthenium ; (and the following, of which little is yet determined) caesium, erbium, terbium, didymium, lan- thanum, niobium, norium, ilmenium, pelopium, thallium. MINERAL GROUPS AND SPECIES. The following list contains the more abundant minerals, arranged in chemical or characteristic groups and sections : Sub-Kingdom Metals and Metallic Ores. NATIVE METALS. Metals occurring in the free or uncombined state. SIMPLE GROUP Gold, silver, platinum, palladium, mercury, copper, iron (?), lead, arsenic, antimony, bismuth, tellurium, zinc, tin (?) DOUBLE GROUP Gold-amalgam, silver-amalgam, platiniridium, iri- dosmine, arsenic-antimony, antimony-silver, arsenic-copper. MIXED or TELLURID GROUP Altaite, nagyagite, sylvanite, hessite, tetradymite. SULPHURETTED ORES. A. SIMPLE SULPHIDES : Metallic ores, as mono-, sesqui-, and di- sulphides. PROTO or GALENITE GROUP Galenite, argentite, naumannite, eukairite, berzelianite, clausthalite, bornite, pentlandite, sphalerite, chalcolite, stronmeyerite, pyrrhotite, cinnabar, Millerite, troilite, Greenockite, nickelite, Breithauptite, covellite, realgar. SESQUI GROUP Orpiment, stibnite, kermesite, bismuthite. DEUTO or PYRITE GROUP Pyrite, cubanite, chalcopyrite, barnhard- ite, stannite, linnaeite, smaltite, cobaltite, ullmannite, marcasite, leucopyrite, arsenopyrite, molybdenite. B. DOUBLE SULPHIDES : Metallic ores, as sulph.-arsenites, s. antimonates, s. bismuthites. SULPHO- SALTS Chalcostibite, zinkenite, Jamesonite, Bournonite, Stephanite, Dufrenoysite, Freislebenite, tetrahedrite, pyrargyrite, boukngerite, Tennantite. 1 6 THE ROCKY CRUST : OXIDISED ORES. Metallic ores, as suboxides, monoxides, binoxides, and derived hydrox- ides ; occasionally compound. IRON GROUP Haematite, magnetite, limonite, ilmenite, iserite, chromite, Franklinite. MANGANESE GROUP Hausmannite, braunite, pyrolusite, manganite, psilolmelane, wad. TIN GROUP Cassiterite, wood-tin. COPPER GROUP Cuprite, chalcotrichite, melaconite. ZINC GROUP Spartalite, zincite. ANTIMONY GROUP Valentinite, senarmontite, cervantite. TITANIUM GROUP Rutile, anatase, brookite. OCHRE GROUP IronO., cobalt O., molybdena O. (molybdenite), bis- muth O. (bismite, antimony O. stibiconite), uranium O. (pitch- blende), lead O. (minium, massicot), chrome O., arsenic O. (arsen- olite). CARBONATED ORES. Metallic ores, as carbonates of oxides. ANHYDROUS GROUP Siderite, rhodocroisite, Smithsonite, man- ganocalcite, cerrussite. (Massive Clay -band and Black-band iron- stones). HYDROUS GROUP Lanthanite, zaratite, hydrozincite, aurichalcite, malachite, azurite, bismutite. SULPHATO-CARBONATES Susannite, Leadhillite, Caledonite. CHLORIDES, BROMIDES, AND IODIDES. Metals in combination "with chlorine, bromine, and iodine. CHLORIDES Calomel, cerargyrite, matlockite, mendipite, atacamite. BROMIDES Bromyrite. IODIDES lodyrite, coccinite. TUNGSTATES, MOLYDATES, CHROMATES. Metallic ores with tungstic, molybdic, and chromic acids. TUNGSTATES Scheelite, stolzite, wolfram. MOLYBDATES Wulfenite, pateraite. CHROMATES Crocoisite, vauquelinite. TITANATES, TANTALATES, COLUMBATES, &c. Metallic ores with titanic, tantalic, and columbic acids. TITANATES Ilmenite, iserine, polymignite. TANTALATES Aeschynite, tantalite, yttra-tantalite. COLUMBATES Columbite, Fergussonite. ANTIMONIATES Monimolite, bleinerite. VANADIATES, ARSENIATES, and PHOSPHATES. Metallic ores with vanadic, arsenic, and phosphoric acids. Occur generally as saline minerals LEAD SALTS Vanadinite, minitesite, pyromorphite. CALCIUM SALTS Haidingerite, pharmacolite. COPPER SALTS Clinoclase, liroconite, erinite, olevinite, copper-mica. IRON AND MANGANESE SALTS Beudantite, vivianite, triplite, childrenite, scorodite, pharmacosiderite, dufrenite. ITS STRUCTURE AND COMPOSITION. I/ COBALT AND NICKEL SALTS Cobalt bloom (erythrite), nickel green. ALUMINIUM SALTS Wavellite, turquoise, lazulite, amblygonite. ZINC SALTS Adamite. SILICATED ORES. Subsilicates, unisilicates, and bisilicates of the metals. ANHYDROUS Ilvaite, hisingerite, anthosiderite, chlorophseite, gado- linite, allanite. HYDROUS Thorite, cerite, chloropal, calamine. Sub-Kingdom Non-Metallic Minerals. SILICATED MINERALS. Silicates of oxides of the earths and alkalies. QUARTZ GROUP (crystalline) rock-crystal, with its varieties ; (com- pact] calcedony, with its varieties ; (compact hydrous] opal, with its varieties. FELSPAR GROUP Anorthite, Labradorite, hyalophane albite, oli- goclase, orthoclase. Amorphous felstones, pitchstones, and obsid- ians. ) CLAY GROUP Kaolin, halloysite, smectite, bole, teratolite, saponite, sinopite, plinthite, bauxite. (Massive and impure clays the results of decomposition.) SCAPOLITE GROUP Scapolite, sarcolite, meionite, dipyre. LEUCITE GROUP Leucite, sodalite, hatiynite, nephelite, lapiz-lazuli. EPIDOTE GROUP Epidote, axinite, Piedmontite, Saussurite, fibrolite, Andalusite, staurolite. GARNET GROUP Garnet, grossularite, py rope, almandite, ouvarovite, helvite, vesuvianite. HORNBLENDE GROUP Hornblende, tremolite, nephrite, actinolite, asbestus, hypersthene, bronzite, diallage, pyroxene, augite, sahlite. (Hornblendic and augitic rocks. ) MICA GROUP Muscovite, margarodite, lepidolite, caryophyllite, phlogopite, biotite, lepidomelane. (Micaceous slates and schists.) TALC GROUP Talc, steatite, agalmatolite, sepiolite, cimolite. (Tal- cose rocks and schists.) CHLORITE GROUP Chlorite, pyrosclerite, ripidolite, margarite, glau- conite. (Chloritic schists and earths.) SERPENTINE GROUP Serpentine, chrysolite, marmolite. (Serpen- tinous rocks.) ZEOLITE GROUP (hydrous) Thomsonite, natrolite, scolezite, mesolite, analcite, prehnite, chabazite, harmatome, stilbite, Heulandite, Brew- sterite. (Occur in geodes and fissures ; never form rock-masses.) CHRYSOLITE GROUP Chrysolite, leucophanite, zircon, spinel, corun- dum, chrysoberyl, topaz, emerald, tourmaline. (In crystals only.) HALOID MINERALS. Non-metallic sparry minerals. (Fluorides, chlorides, carbonates, nitrates, sulphates, &c.) CALCITE GROUP (carbonates] calcite, dolomite, hydrodolomite, mag- nesite, hydromagnesite, arragonite. (Massive and subcrystalline limestones and marbles.) (Phosphates} apatite (Phosphatic and co- prolitic nodules). B 1 8 THE ROCKY CRUST: FLUORITE GROUP (fluorides) fluorite, yttrocerite, fluocerite, cryolite. HEAVY-SPAR GROUP (carbonates) witherite, barytocalcite, bromlite, strontianite ; (sulphates) barite, celestite. GYPSUM GROUP (sulphates] gypsum, selenite, satin-spar, alabaster, glauberite, anhydrite, polyhalite. HALITE GROUP (chlorides] halite (rock-salt), sylvite, sal-ammoniac, carnallite; (carbonates) natron, trona, thermonatrite ; (nitrates} nitre, nitratine, nitro-calcite, nitro-magnesite ; (sulphates} epsomite, lowite, thenardite, mirabilite, kalinite (alum), alumite, apjohnite, halitrichite ; (borates) borax, sassolite, boracite, hydro-boracite. ORGANIC SALTS (oxalates} Whewellite, Humboldtite ; (mellitates} mellite. The INFLAMMABLES. SULPHUR GROUP Sulphur, selen-sulphur. CARBON GROUP Diamond. CARBONACEOUS GROUP Graphite, anthracite, common coal, jet, lignite, peat. (Coal in its numerous varieties.) HYDROCARBONS (simple} naphtha, petroleum, maltha, elaterite, asphalt, albertite, ozocerite, hatchetine ; (oxygenated) succinite (amber), ambrite, copalite. MIXED ROCKS. The " Mixed Rocks " constitute, as has been already stated, the main bulk of the earth's crust. They may consist of two or more mineral ingredients, and are often of very varied and irregular composition. Without rigid adherence to mineralo- gical exactitude, they may be arranged, according to their predominating or more obvious ingredients, into the following groups. We give such explanations as may enable the non- mineralogical reader to understand their distinctive character- istics. (Arenaceous or Fragmentary Group.} Sand is in general a loose aggregation of water-worn particles, arising from the disintegration of pre-existing rocks or other mineral matter. It occurs in many varieties, as quartz-sand, shell-sand, coral-sand, iron-sand. The finely comminuted particles of volcanic matter are spoken of as volcanic sand. Gravel is the term applied to water- worn fragments of rocks when the particles or pebbles vary from the size of a pea to that of a hen's egg. There are many varieties, according to the nature of the rocks from which these may be derived, as flint-gravel, quartz-gravel, &c. Shingle is the geological term for water-worn rock-fragments larger and less rounded than those of gravel. Shingle beaches are common on the more exposed portions of sea-coasts. Rubble is a convenient and expressive term, applicable to accumulations of angular rock-fragments indiscriminately thrown together, and such as may arise from river-floods, ice-drift, or the action of frost on cliffs and pre- cipices. Boulder is a term applied to the larger water- worn blocks of stone found on the soil or amid the superficial material. They usually owe their origin ITS STRUCTURE AND COMPOSITION. 19 to the ice-drifts of the glacial period, but occasionally also to wave-action, as the " Boulder Beach" of Appledore. Block is the term applied to the more angular masses ; hence such phrases as " blocks and boulders," "perched blocks," &c. Sandstone is simply consolidated sand, the particles having been com- pacted by pressure, or cemented together by lime, clay, iron-oxide, or other material. Grit is the term applied to a sand-rock, when the particles are hard and irregular that is, "sharper" than in ordinary sandstones. Conglomerates (sometimes termed Pudding-stones} are aggregates of gravel and pebbles of all sizes in other words, consolidated gravel. According to the size of the fragments, geologists speak of " pebbly conglomerates and " bouldery conglomerates." Breccias (Ital. breccia, a crumb), are agglutinations of angular fragments, which have not suffered attrition, as in the pebbles of conglomerates. (Argillaceous or Clayey Group.} Clay is a fine impalpable sediment from water, and consists wholly, or almost so, of alumino-silicious particles. It is usually tough and plastic, and is of various colours, according to the presence or absence of organic matter and metallic oxides. Fire-clay is a variety usually obtained from the coal formation, and is so called from its power of resisting the strongest action of heat a property it acquires from its freedom from alkaline earths, such as soda, potash, and lime. Fullers' Clay or Earth is a hydrous silicate of alumina, employed, from its absorbent nature, in the scouring or fulling of greasy woollens ; hence the name. Mud is the familiar as well as technical term for the fine impalpable matter worn and borne down by water, and deposited in seas, lakes, and estuaries, it is often a very miscellaneous admixture, partly of mineral and partly of vegetable and animal origin. Silt is the general term for the miscellaneous matter deposited in lakes, estuaries, bays, river-reaches, and other still waters. It may consist of intermingled mud, clay, and sand, or of distinct layers of these. Shale is merely consolidated mud, assuming a structure less or more laminated, and very variable, of course, in composition. Mudstone is a convenient term employed by geologists to designate an earthy clayey rock, void of shaly lamination, and often of compact and homogeneous texture. Slate is often applied indiscriminately to all hard, laminated, argillaceous rocks, that can be readily split up ; hence slaty sandstone, mica-slate, clay- slate, &c. It would be better, however, to restrict the name to the clay- slates or roofing-slates. Claystone, the name applied by the older mineralogists to the softer and earthy varieties of felstone or felsite, and now almost obsolete. (Calcareous or Lime Group.} Limestone is the general term for all rocks, the basis of which is car- bonate of lime that is, lime in union with carbonic acid. Calcareous rocks are all less or more acted upon by the ordinary acids, effervescing on the application of these liquids. Marble is an architectural rather than a geological term, and is applied to the compact, crystalline, mottled, and veined varieties of limestone susceptible of a fine polish. 20 THE ROCKY CRUST: Chalk is a familiar as well as a technical term for the softer and earthier varieties of limestone. The chalks appear in various colours. Calc-tuff and Calc-sinter are precipitates or deposits from calcareous waters, and appear as porous, incrusting, stalactitic, and stalagmitic masses. Marl is a loose application for all friable compounds of lime and clay. The marls of fresh- water lakes are spoken of as "clay-marls," "marl- clays," and "shell-marls," as one or other ingredient predominates. Gypsum is a sulphate of lime, which when calcined forms the well-known plaster of Paris or stucco. It occurs massive-crystalline, granular, or fibrous, and when crystallised is known as selenite. Alabaster is the term applied to fine translucent varieties of carbonate of lime and of sulphate of lime, the former being known as calcareous, and the latter as gypseous, alabaster. Magnesian limestone is a compound of carbonate of magnesia and car- bonate of lime ; but as many limestones contain a small portion of mag- nesia, the term is generally restricted to those containing from 18 or 20 per cent and upwards. Dolomite (after the French geologist Dolomieu) is a granular or crystal- line variety of magnesian limestone. (Silicious or Flinty Group.'] Quartz, properly speaking, is fine silica ; rock-crystal is the name given to clear, transparent, crystallised varieties ; and coloured varieties are known as amethyst, cairngorm, topaz, &c. Quartz-rock is massive quartz of various colours, and occurs in veins or stratiform masses. Quartzite is the term applied to granular varieties, and to sandstones apparently reconverted by heat or chemical change into quartz. Jasper, Agate, Carnelian, Hornstone, Lydian stone, &c., are compact silicious rocks and minerals of various colours, exhibiting smooth or con- choidal fractures. Flint is nodules of impure silica of various colours, and usually found in chalk and limestone strata. Chert is the name given to highly silicious limestones or admixtures of flint and limestone, and occurs in concretions, nodules, and rock-masses. Calcedony, Opal, Silicious-sinter, &c., are silicious minerals, generally .produced by infiltration of water holding silica in solution, and appearing as incrustations of greater or less thickness. (Carbonaceous and Bituminous Group.) Coal is a well-known substance, and may be briefly described as miner- alised vegetable matter, containing more or less of earthy impurities. It occurs in many varieties, as caking or coking coal, splint or slaty coal, cubic or rough coal, cannel-coal, &c., which are all bituminous, giving off smoke and flame in burning ; and also as anthracite or stone-coal, which is non-bituminous, and burns without smoke or flame. Lignite^ also known as wood-coal, board-coal, and brown coal, is a vari- ety of recent formation, and in which the woody structure is still apparent. Indeed, the transition from peat to lignite, from lignite to coal, and from coal to anthracite, is often so apparent, that there can be no doubt that they are all merely vegetable masses in different stages of mineralisation. Jet is a compact, lustrous variety of coal, susceptible of a high polish, and on that account usually worked into personal ornaments. Graphite (familiarly known as plumbago and black-lead, from its appear- ance, though entirely devoid of lead) is almost pure carbon, containing only slight traces of iron and earthy impurities. ITS STRUCTURE AND COMPOSITION. 21 Bitumen is an inflammable mineral substance (hydrocarbon), found either in a free or in a combined state. As free bitumen, it occurs limpid, as naphtha ; liquid, as petroleum or rock-oil ; slaggy, as maltha or mineral pitch ; and solid, as asphalt. It can be discharged from coals, coaly shales, and other substances, by the application of heat ; hence such sub- stances are said to be "bituminous," or more properly " bituminiferous. " (Saline or Salt-like Group.} Common Salt (chloride of sodium) is found in incrustations in desiccated sea-beaches, and in the sites of dried-up lakes. It occurs abundantly in the solid crust as rock-salt, and is held in solution by all sea-water and brine springs. Nitrates of Soda and Potash (natron, trona, saltpetre, &c.) occur as in- crustations and efflorescences in many plains, marshes, and lakes in hot countries. Such deposits or salinas are often of considerable thickness and extent. Alum (sulphate of alumina and potash), though chiefly extracted for commercial purposes from certain shales and schists, is also found in nature in the saline or crystallised state. Borax (borate of soda), another saline product, boracic acid being abun- dantly discharged by the thermal springs of some volcanic regions. Borate of Lime, another saline substance occurring in radiated nodules, is a product of salinas, such as those of Bolivia and Peru. Sulphur is found massive and in crystals in almost all volcanic districts. It is also found largely in combination with many of the earths and metals. (Simple Minerals and their Rock Compounds. ) Felspar (a chemical admixture of silica, alumina, and potash or soda) is a softer mineral than quartz. The larger and softer crystals occurring in granite are of felspar ; they can be scratched by the knife when quartz resists it, and can also be distinguished by the flat glassy aspect of their cleavage. Compact Felspar, Felstone, or Felsite, is a massive, amorphous, felspathic rock, forming dykes and mountain-masses. Porphyry and Felspar Porphyry are rocks mainly composed of compact felspar, with interspersed crystals of felspar. Mica (Lat. mico, I glisten) is a soft, sectile mineral, readily splitting up into thin transparent plates, and is a chemical compound of silica, mag- nesia, and potash. The glistening scaly crystals in ordinary granites are mica. Mica-schist and Mica-slate are schistose or slaty rocks, largely composed of micaceous particles the former splitting irregularly, the latter with greater flatness and regularity. Hornblende, Hornblende-rock, Hornblende-schist. As a mineral, horn- blende is of a dark or dark -green colour, with a horny glistening lustre (hence the name), and occurs largely as a constituent of certain greenstones and granites. When massive, it constitutes hornblende-rock ; when fis- sile, hornblende-schist. Hypersthene is a greenish-black or greenish-grey mineral, having some- what of a metallic lustre, nearly allied to hornblende, and occurring largely in igneous rocks, or forming independent rock-masses. Actynolite (Gr. actin, a thorn), another mineral closely allied to horn- blende of a glassy lustre, and deriving its name from the thorn-like shape and disposition of its crystals. It occurs massive, as Actynolite-rock and fissile, as Actynolite-slate. Augite, a black and harder mineral than hornblende, forming the princi- pal constituent of the basalts and clinkstones. 22 THE ROCKY CRUST: Asbestos or Amianthus, so well known from its fine fibrous texture, may be regarded as a variety of actynolite. It occurs in flexible fibres, in rigid masses, and in tough aggregates known as "mountain wood," "mountain cork," " mountain leather," &c., from its resemblances to these substances. Chlorite (Gr. chloros, greenish-yellow) is a mineral of a greenish hue, and generally of a foliated texture, in which condition it forms the principal ingredient in the rocks known as chlorite-slate and chlorite-schist. Talc, a whitish-green magnesian mineral, closely allied to and resembling mica. It is transparent in thin plates, but is generally massive, sectile, soft, and non-elastic. It enters largely into the earlier schists, known as talc-schists and talcose-schists. Steatite, Stea-schist, Soapstone, Potstone.A\\ rocks containing steatite, which may be regarded as a variety of talc, have a greasy or soapy feel, hence the name, from stear, fat or grease. Some from this feel are termed soapstone ; others, from their sectility and power of resisting heat, are known and used as Potstones. Serpentine, so called from its variegated or mottled hues, like the skin of a serpent, is one of the magnesian rocks, occurring largely in primitive districts, and employed as an ornamental stone. {Igneous or Pyrogenous Rocks. ) Granite and Syenite. Ordinary granite is a granular-crystalline com- pound of quartz, felspar, and mica, and variously coloured from the presence of iron in the felspar, or from the hues of the mica. There are many vari- eties of granite, differing in size of grain, colour, and compactness. When hornblende takes the place of mica, or when present in addition, the rock is usually known as Syenite, from Syene in Upper Egypt, where it was early quarried. Trap-Rocks (from Swedish Irappa, a stair, owing to the step-like or terraciform aspect they give to the hills composed of them) include a great variety of igneous rocks all less crystalline than the granitic, and all more compact and less vesicular than volcanic products. These are the basalts, clinkstones, greenstones, felstones, pitchstones, amygdaloids, tuffs, and ashy agglomerates. The basalts, clinkstones, and greenstones are generally hard, close- grained, subcrystalline rocks, often assuming columnar and subcolumnar structures. They consist of varying admixtures of felspar, augite, and hornblende. The. felstones, amygdaloids, and trap-tuffs are softer and less crystalline rocks the felstones compact or earthy ; the amygdaloids having their vesicular cavities filled with agate, carnelian, calc-spar, &c ; and the tufas evidently consolidated ejections of dust and ashes. The Volcanic Rocks consist of lavas, obsidians, pumice, scoriae, ashes, lapilli, sulphurous muds, &c. , and occur, according to their age, from rocks differing little from greenstones and basalts to loose accumulations of dust and cinders. The Trachytes are rough - grained (Gr. trachys, rough) subcrystalline varieties of felspathic lava. The Lavas proper occur in many varieties porous, vesicular, compact, basaltic, subcrystalline ; glassy, as obsidian and light and cellular, with silky-fibrous texture, as pumice. Scorice, lapilli, bombs, dust, sand, &c., are the familiar names for the loose and fragmentary ejections. ( The Metallic Group. ) The metals are found either native that is, in a pure state or combined with mineral matter in the state of ores. Gold, silver, platinum, copper, ITS STRUCTURE AND COMPOSITION. 23 and one or two others, are found native in nuggets, pellets, plates, and thread-like branches ; the majority of the metals occur as ores that is, as oxides, sulphides, carbonates, &c., as shown in the tabulation of mineral groups, p. 15, 16. Most of these ores are found in veins associated with sparry matter, as calc-spar, fluor-spar, quartz, baryta, &c., which form the veinstone, gangue, or matrix ; a few only occur as stratified deposits. II. CHRONOLOGICAL ARRANGEMENT OF ROCK-FORMATIONS. It is not enough, however, to determine merely the posi- tions, structure, texture, and composition of rocks ; the geo- logist must endeavour to ascertain their relative ages that is, their succession in time and sequential place in the earth's crust, so as to be able to map out their respective areas, their extent, thickness, and abundance. In this task he is mainly aided by three considerations superposition, mineral com- position^ andjos^nj^naains. In any succession of deposits it is obvious tHatlhe lowest must be the oldest, and that those above will take their places in chronological order. It is also for the most part true that the older and deeper strata will have undergone a higher degree of internal or mineral change through pressure, chemical replacement, and other metamor- phosing agents. And it has been further ascertained that the older or deeper any rock-formation is, the more widely do its organic remains differ from existing genera and species. Guided in his determination by these and similar truths, the geologist has been enabled to arrange the stratified rocks in chronological sequence that is, into formations, groups, and systems or life-periods, from the deposits now taking place in existing waters to the deepest or most ancient in the earth's crust, and about whose nature and origin he can reason with something like certainty. Having determined the relative ages of the stratified rocks, he also attempts a similar arrange- ment of the unstratified or igneous, being guided in this attempt by the strata through which they pass, by the frag- ments of other rocks they may enclose, and lastly, by the manner in which they intersect and overlie each other. Classification of Stratified Deposits. In this classification of stratified deposits, the geologist understands by a formation any series of strata that has been deposited continuously in the same area, be that lake, estuary, or sea; and hence he speaks of lacustrine, estuarine, and marine formations. By a group he embraces such strata as have several lithological and palaeontological features in com- mon, though they may be partly of fresh-water and partly of 24 THE ROCKY CRUST: marine origin. And under a system or life-period, he includes such formations and groups as present the same general facies of fossil remains that is, such groups as are characterised by the presence of the majority of the same plants and animals. Abiding by these principles, modern geologists have arranged the stratified rocks of the crust, and especially those of Europe, as in the annexed tabulation the terms Primary or Palaeozoic (ancient life), Secondary or Mesozoic (middle life), and Tertiary or Cainozoic (recent life), being analogous to the subdivisions of human history into ancient, medieval, and modern : TABULAR SYNOPSIS OF EUROPEAN STRATA. Group, Recent. Post- Pliocene. Newer Pliocene. Older Pliocene. Miocene. Upper Eocene. Middle Eocene. Lower Eocene. Maestricht Beds. Upper White Chalk. Lower White Chalk. Upper Greensand. Gault. Lower Greensand. Wealden Clays and Sands. Purbeck Beds. Portland Stone. Kimmeridge Clay. Coral Rag. Oxford Clay. Great or Bath Oolite. Inferior Oolite. Lias Marls and Shales. Lias Limestones. Upper Trias. Middle, or Muschelkalk. Lower Trias or Bunter. Magnesian Limestone. Variegated Sandstones. Upper Coal-Measures. Millstone Grit. Carboniferous Limestone. Lower Coal-Measures. Sandstones and Limestones. Sandstones and Conglomerates. Upper Limestone and Shales. Lower Slates and Grits. Slates, Grits, and Schists. Schists, Quartzites, Serpentines. Crystalline Schists. Systems. I POST-TERTIARY. I PLIOCENE. MIOCENE. I EOCENE. Cycles. i CRETACEOUS. u N P^ CJ OOLITIC OR Q O JURASSIC. > - P4 ^S O C/3 W ^> C/3 * ' TRIASSIC. > PERMIAN. ) > y J > CARBONIFEROUS. 3-1 ) S o j DEVONIAN. % 3 3 ? SILURIAN. (X * CAMBRIAN. LAURENTIAN. METAMORPHIC. AZOIC. ITS STRUCTURE AND COMPOSITION. 25 In further explanation of the preceding synopsis, it may be stated that the Post-Tertiary System consists in the main of clays, gravels, sands, peat-mosses, marls, coral-reefs, foramini- feral muds, and other accumulations, which are still forming, or which have been formed within a comparatively recent period, in lake-basins, river- valleys, estuaries, and along the shores as well as in the depths of the ocean. They imbed, in a sub-fossil state, the remains of plants and animals still living, though often removed from, or extinct in, certain locali- ties which they once inhabited. In volcanic districts they are associated with lava, scoriae, and other igneous ejections : and, generally speaking, they occupy low-lying tracts, and constitute the surfaces of valleys, plains, and other alluvial expanses. Immediately underlying these recent deposits, there occur over the northern hemisphere (down to the 40th parallel of latitude or thereby) thick accumulations of clay and gravel, imbedding huge water-worn blocks or boulders ; and as these seem to point to a time when large areas of the northern hemisphere were under ice, or subjected to the drift of icebergs that dropped their burdens of clay, gravel, and boulders on the then submerged surface, this period is generally known as the Boulder, Northern Drift, or Glacial Epoch, and holds a place intermediate between the Post-Tertiary and Tertiary Systems. For the most part, these glacial accumulations dre destitute of organic remains, but in some of the upper and laminated clays, shells, star-fishes, bones of birds, seals, and whales make their appearance, and these are all strictly of boreal species. The Tertiary System consists, in general terms, of clays, sands, gravels, limestones, marls, and lignites, or beds of wood- coal, and occupies well-defined areas (Basins}, as if these at one time had been extensive fresh-water lakes, estuaries, and inland seas. The fossils imbedded in tertiary strata, though closely allied to existing genera and species, are in most instances extinct, and point to conditions of climate and dis- tributions of life very different from that at present prevailing. The igneous rocks associated with them are lavas and basalts, the products of volcanoes long since extinct, or now but partially active. Undulating lowlands may be said to con- stitute, the physical features of tertiary tracts the basins of London, Paris, and Vienna, and the upper pampas of the La Plata, being typical examples. The Cretaceous or Chalk System consists, as its name implies, of thick beds of chalk or soft marine limestones, associated with sand, sandstones, clays, and in some localities with beds of coal and lignite. The fossils belong almost wholly to ex- tinct species ; and even where the chalk beds are wanting, the 26 THE ROCKY CRUST: other strata are so replete with the characteristic remains of the system (sponges, foraminifera, sea-urchins, shell-fish) that there is generally little difficulty in recognising it. The associ- ated igneous rocks are chiefly basalts and greenstones ; and the physical features of the system may be said to be low rounded hills (like the " Downs " of Kent, Surrey, and Sussex), with dry intermediate depressions (coombs) where the chalks and sand prevail, and flat fertile vales, where the rich fossiliferous clays come to the surface. The Oolitic or Jurassic System consists largely of limestones, alternating with calcareous clays, sandstones, bituminous shales, and, in some districts, of beds of ironstone and work- able coals. It derives its former name from its peculiar lime- stones or roestones (Gr. oon, egg ; lithos, stone), which have a minutely concretionary texture ; and its latter from its exten- sive development in the Jura Mountains. Palaeontologically, it is characterised by its cycadaceous plants and tree-ferns, by its abundant marine fauna (corals, bivalves, and nautilus- like ammonites), and by its huge aquatic and terrestrial rep- tiles. The unequal weathering of its harder limestones, soft clays, and shales, confers on the oolitic landscape that succes- sion of long undulations so noticeable in that broad belt of country which stretches from Yorkshire on the north-east, to Dorset on the south-west of England. The Triassic and Permian Systems, which were formerly considered as a single system under the name of the New Red Sandstone, consist in the main of soft reddish (sometimes pebbly) sandstones, yellowish magnesian limestones, and va- riegated clays and marls, with occasional deposits of rock-salt and gypsum. The lower portion, being largely developed in Perm in Eastern Russia, has given rise to the term Permian ; and the upper, consisting in Germany of three well-marked members (sandstones, limestones, and marls), has received the name of Trias, or triple group. The fossil remains of these systems differ widely those of the Permian being closely allied to the Carboniferous flora and fauna, and therefore Palaeozoic ; while those of the Trias are Mesozoic, and consist of marine organisms, with footprints of birds and amphibian reptiles. The physical features of the New Red Sandstone are by no means decided the limestones and harder sand- stones forming inconspicuous hills and ridges, the softer clays and marls being worn into vales and expanses, of a flat, moist, and retentive character, better fitted for pasture than for corn- culture, and of which Cheshire, in our own country, may be taken as a typical example. ITS STRUCTURE AND COMPOSITION. 2/ The Carboniferous System, so called from its yielding the main supply of coal (Lat. carbo, coal) in Europe and America, consists of sandstones, shales, clays, limestones, ironstones, and coals in frequent alternations, as if they had been depo- sited for ages in seas and estuaries, subjected to repeated subsidences and elevations. The fossils of the system are abundantly marine, estuarine, and terrestrial, and all of palae- ozoic forms the most notable being that excess of vegetable growth that went to the formation of numerous seams of coals. With the exception of the trap hills (greenstones, basalts, amygdaloids, &c.) that intersect the system in some localities, and those bold cliffs and scars of limestone (mountain lime- stone) so characteristic of Yorkshire and Derbyshire scenery, there is little attractive in the physical features of the coal-for- mation, monotonous moorlands of cold retentive soil (Nor- thumberland, Lanark, Linlithgow) being a common occurrence in the geography of the system. Though superficially unat- tractive, it is rich in mineral and metallic products coals, lime- stones, fire-clays, building-stones, ironstones, and ores of lead, zinc, silver, and antimony, being among its most important contributions to modern industry and civilisation. The Old Red Sandstone or Dei'onian System (from Devon- shire, where a portion of it is typically developed) consists in the main of reddish sandstones, conglomerates, flagstones, and shales, with subordinate beds of limestone. In Devon the fossils are chiefly corals, shells, and other marine exuviae ; in Hereford and Scotland, Crustacea and fishes prevail. Thrown into many irregularities by trap (often felstone) eruptions, the physical features of the Old Red Sandstone are usually varied and picturesque, and in general its slopes are dry and of moderate fertility. The larger portions of Devonshire, Here- ford, Perthshire, and Forfar, as well as of the south of Ireland, may be taken as typical areas of Old Red Sandstone. The Silurian System (so called from its typical development in that district of Wales anciently inhabited by the Silures) consists of numerous slaty or hard shaly beds, with sandstones, grits, and intercalated limestones. As in all the older and deeper-seated formations, there is a tendency to crystalline texture, and these are not unfrequently traversed by metallifer- ous veins tin, copper, silver, and gold. Its fossils are emi- nently marine, and consist almost wholly of the invertebrate orders (corals, shell-fish, and Crustacea), few fishes being found in its strata, and these only in the upper portions of the sys- tem. Flanking and often borne up by the older granitic hills, the physical features of the system are frequently irregular and 28 THE ROCKY CRUST : mountainous; but, from the softer nature of the rocks, are more rounded and massive, and less abrupt and precipitous, than those of the crystalline or metamorphic' strata. Western Wales and the southern uplands of Scotland, from St Abb's Head on the east to Portpatrick on the west, with all their variety of hill, glen, and valley, may be taken as typical areas of Silurian soil and scenery. The Cambrian and Laurentian Systems (so called, the former from being typically developed in Wales ; and the latter, from its vast development in the Laurentide mountains in Canada) consist, for the most part, of slates, grits, quartzites, schists, serpentines, and other crystalline strata. Being chiefly altered rocks, they contain few fossils, and present in their geogra- phical features peaks and splintery pinnacles, with steep preci- pices and ravines thus conferring on their areas picturesque and romantic scenery, like that of Wales and the lake district of Cumberland; or still more irregular and mountainous regions, like those of the Laurentian and Norway Highlands. The Metamorphic System (so called because its strata have undergone a metamorphism or change by heat, pressure, and chemical action, from ordinary sandstones, shales, and lime- stones into hard crystalline schists) consists of such rocks as gneiss, quartzite, mica- schist, slates, serpentines, and primi- tive marbles. They yield no fossils ; but whether all traces of life may have been obliterated by the mineral change these rocks have undergone, or whether they were deposited before life existed on the globe, Geology cannot determine. These crystalline schists are generally found at high angles, flanking or composing the main mass of the older mountains ; and from their hard splintery nature, present those peaks and ridges that confer on primitive districts their abrupt, wild, and Alpine character. Classification of Unstratified Rocks. As with -the stratified so with the unstratified rocks ; each great group has its own physical features, and though perhaps less sharply defined, they are still sufficiently distinct to be recognised in hill and mountain ranges as Volcanic, Trap- pean, and Granitic. The Volcanic are generally associated with the more recent stratified formations, and consist of trachytes, basaltic lavas, ves- icular lavas, scoriae, and other similar products loose and less consolidated in the more recent and active, and harder and more compact in the older and extinct volcanoes. They rise up in dry rocky hills, more or less conical and crateriform; and ITS STRUCTURE AND COMPOSITION. 29 these are, perhaps, more frequently grouped round some com- mon centre than arranged in linear or axial directions. The cones of Vesuvius and Etna, and the crateriform hills of Au- vergne, are familiar and well-known examples the slopes varying in abruptness from peaks of scoriae, and less abrupt mixtures of scoriae and lava, to the flatter hills composed mainly of lava or liquid ejections ; hence the familiar designa- tions of cinder-cones, mixed-cones, and lava-cones. The Trappean (so called from the terraciform aspect of many of the hills they compose Swedish, trappa, a stair) con- sist of greenstones or whinstones, basalts, felstones, por- phyries, amygdaloids, tufas, and other kindred rocks, and are generally associated with the secondary and upper primary strata. They are usually elevated into hill-ranges more or less persistent, and from their higher antiquity and longer subjec- tion to wasting influences, are now worn into rounded heights, exposed crags, slopes, and terraces, which confer on the land- scape a beauty and diversity peculiarly their own the harder basalts and greenstones standing out as the crags and terraces, while the softer tufas and ashes have been worn down into gentle slopes and declivities. Their soils being dry and genial, the " trap-soils " of a country are generally possessed of great amenity and fertility, and constitute, perhaps, the most valuable agricultural portions of the districts in which they occur. The Granitic, or oldest series of igneous rocks, consists of granites, syenites, porphyries, and the like, which, from their more ancient and deeper-seated relations, are generally hard and crystalline in texture, and massive in structure. They constitute the nucleus or backbone, as it were, of all the higher and older mountain-chains elevating the metamorphic schists into splintery peaks and abrupt ridges, or presenting of themselves broad massive shoulders of cold sterile moorland and unprofitable heath. Geological Maps and Sections. To map out the areas occupied by these respective systems, and to exhibit the thickness, alternations, and relations of their strata by sections and sketches, is the task of the field geologist. The areas occupied by the respective formations are generally marked by distinctive colours, as in the map of the British Isles which accompanies this volume; and the alternations, dips, faults, &c., of the strata are exhibited by sketch-sections. These sections are constructed from obser- vations of outcrops, exposures in sea-cliifs, ravines, railway and 3O THE ROCKY CRUST: road cuttings, borings and sinkings of wells, coal-pits, and the like. Wherever a rock comes to the surface, or can be seen, its place and dip are noted down ; and by a careful succession of such jottings wonderful approximations to the actual struc- ture of any locality can be arrived at. By certain conventional signs arrows for dips, bold lines for outcrops, white lines for faults, coloured lines and masses for igneous dykes and erup- tions, bronzed lines for veins, and the like a vast amount of geological information can be at once conveyed to the eye, while descriptive notes supply the details of mineral and other peculiarities. It must not be supposed, however, that the space coloured on a map exhibits the absolute extent of any formation, for a large amount of that formation may be cov- ered or overlaid by more recent formations a circumstance which can often be inferred with great accuracy, but which can only be proved by direct exploration. Such maps as are here spoken of exhibit the extent, thick- ness, dip, and other relations of the solid rock-formations only. But as these formations are, for the most part, overlaid by clays, sands, gravels, peat-mosses, alluvial silts, and other superficial accumulations, and as these accumulations are often of agricultural and commercial importance, they require a separate survey and mapping. In fact, every well-conducted geological survey should have two sets of maps one exhibit- ing the superficial accumulations, and another the subjacent rock-formations. Provided with two such maps, the farmer, builder, engineer, miner, or technologist, should have no diffi- culty in arriving at some estimate of the amount, quality, and facilities of obtaining the industrial products of any locality the value of the maps depending, of course, upon the minute- ness and accuracy of the survey. The value of the maps is greatly enhanced by well-constructed sections, showing the successive alternations and thicknesses of the respective strata, though for special purposes a section is generally obtained by boring or pitting the locality in question. In the preceding chapter we have drawn attention to the structure and composition of the Rocky Crust from which all our industrial products mineral and metallic are derived. Some acquaintance with its rocks their origin, relative posi- tions, structure and texture, mineral composition, and chrono- logical succession is indispensable to the thorough utilisation of its products. The crust of the earth has a masonry of its own; every course or system in that masonry has its own peculiarities, and without some knowledge of these peculi- ITS STRUCTURE AND COMPOSITION. 31 arities the practical man is working at hazard and in uncer- tainty. This information we have attempted to supply in the preceding sketch : those who would enter into details must apply to the pages of some work on General Geology. In the mean time, what we have given will render more intelli- gible the following chapters, whether devoted to farming, building, engineering, mining, heating, lighting, or other tech- nological purposes. Works which may be consulted. Lyell's ' Student's Elements of Geology;' Dana's ' Manual of Geology ; ' Juke's ' Manual of Geology ' Geikie's Edition ; Page's ' Advanced Text-Book of Geology;' Tale's ' Rudimentary Treatise on Geology.' III. GEOLOGY AND AGRICULTURE. THE relations between Geology and Agriculture are direct and immediate : the nature and composition of soils, their improvement by admixture and drainage, and their enrichment by manures, being subjects on which landowner and farmer can frequently obtain important information from the practical geologist. A soil may be deficient in composition and texture, and yet the elements of improvement may lie in another soil on the same farm : the question of drainage depends much on the nature of subsoils and subjacent rocks; and substances having a manurial value may be close at hand, and yet be un- suspected by the working farmer. On all such points the geological surveyor can render valuable assistance ; and it is often more through the indolence of routine than through pre- judice that the agriculturist fails to avail himself of the sugges- tions of science. It is true that by some the bearings of geology on agriculture have been overstated, and their value exaggerated ; but it is equally true that the chances of success are on the side of the farmer whose practice is directed by a knowledge of the facts and principles which lie at the founda- tion of his art. Nor for the farmer alone, but for the country at large, is it desirable that scientific principles should rule more thoroughly in practical agriculture. The area of our country is limited, and of that limited area a large portion, partly from structure and partly from climate, is totally unfit for general husbandry; hence the necessity (with an ever- increasing population) that the available portion should be rendered as fertile as it is possible for skill and industry to accomplish. In the present chapter we intend to direct atten- tion,^^/, to the geological character of soils and subsoils, and the possibility of their permanent improvement by intermixture and by drainage ; and secondly, to those mineral manures which modern agriculture has applied with such success alike to the increase and to the earlier ripening of our white and green crops. SOILS AND SUBSOILS. 33 I. SOILS AND SUBSOILS. The soils upon which the agriculturist has to operate are usually classified as sandy, sandy or light loams, loams, clayey loams, heavy or retentive clays, marls, calcareous loams, peaty soils, or bog-earths. This classification has reference chiefly to composition and texture, a special chemical composition (silicious, calcareous, &c.) being necessary for the profitable growth of particular crops, and a certain mechanical texture (friable, porous, &c.) suiting best for the permeation of rain and air, and the descent or spreading of special roots and rootlets. Loams, consisting of fertile admixtures of sand, clay, and kumus or decayed vegetable matter, may be regarded as typi- cal soils, which become, on the one hand, light, by a prepon- derance of sand, and on the other, heavy, by a preponderance of clay. But whatever their composition and texture, these soils, geologically speaking, are mainly of two sorts, soils of disintegration, arising from the waste and decay of the imme- diately underlying rocks, together with a certain admixture of vegetable and animal debris ; and soils of transport, whose ingredients have been brought from a distance, and have no geological connection with the rocks on which they rest. Under the former are comprehended such as arise from the disintegration of limestones, chalks, traps, granites, and the like, and which are directly influenced in their composition, texture, and drainage, by the nature of the subjacent rocks from which they are derived. Under the latter are embraced all drift and alluvial materials, such as sand, shingly debris, miscellaneous silt and clay, which have been worn from other rocks by meteoric agencies, and transported to their existing positions by winds, waters, or ancient glacial agencies. Besides these there are also soils of organic origin, such as peat-earths, and vegetable mould or humus, which is to a great extent also of animal origin or elaboration. Indeed, in all superficial soils there is a certain amount of vegetable and animal matter the decay of plants, the droppings of animals, the exuviae of in- sects, the casts of the earth-worm, and the like, conferring upon them that dark, friable, and loamy character so indica- tive of richness and fertility. Beyond the soils proper, which come immediately under the plough, there are in most situations a set of subsoils, differing from the true soils, and which cannot be ignored by the farmer. Thus peat may lie upon clay, sand upon clay, common humus on sandy clay, and clay may rest upon shingly C 34 GEOLOGY AND AGRICULTURE. debris ; while in many of our alluvial flats (old lake-sites and estuaries) there may be several alternations of peaty matter, clay, sand, silt, and marl, before the underlying rock-formation is arrived at. In general, the subsoils differ notably in colour and consistence from the soils above them. The true soils are usually of a darker colour, from the larger admixture of humus, while the subsoils are lighter in hue yellow, red, or bluish, from the greater preponderance of iron oxides. The soils are also more or less friable in their texture, while the subsoils are tougher, more compact, and more largely commingled with rubbly and stony debris. The soils are usually little more than a mere surface covering, while the subsoils may be many feet, or even yards, in thickness. All these soils and subsoils repose on the rocks below, but it is only where they are immediately derived from these rocks by disintegration that they are materially influenced by this relation. Hence, for agricultural purposes, it is necessary to have two sets of geological maps one showing the range and disposition of the older rocks, and another exhibiting the dis- position of the superficial accumulations by which these are masked. On examining two such maps of any district in Britain, it will be seen that the soils of disintegration occupy limited areas in comparison with those of transport. In all our river-valleys, dales, levels, fens, straths, and carses, the soils are those of transport, and consist of miscellaneous river- drifts, the alluvia of former lakes and sea - beds, or of the sands, shingles, and bouldery clays of the glacial epoch. Over the higher uplands largely over carboniferous districts, and on many of the other formations the drifts of the glacial period are thickly spread; so that it is chiefly on the hilly portions of the Chalk, the Oolite, the Mountain-limestone, the old Slates and Schists, the Traps and Granites, that we find soils of disintegration. And even there, there are many patches of bouldery clay, sand, and shingly drift, whose ma- terials have been brought from other and distant localities. Soils of Disintegration. All rock-surfaces, however hard and refractory, break up, in course of time, under the influence of meteoric agencies. Those containing lime are acted upon by the carbonic acid of the atmosphere; those containing iron by the oxygen; and all suffer more or less through frosts, rains, winds, and other kindred forces. These disintegrating agencies are further aided by the root-growth of plants, by the burrowing of worms and other earth- dwelling creatures, and in no small degree by SOILS AND SUBSOILS. 35 the acids (humic, geic, and crenic] generated by organic decay. From the hardest granites, basalts, and lavas, to the softest chalks and marls, all are undergoing this disintegration ; and the soils thereby produced will vary in depth, composition, and texture, according to the softness and mineral character of the rocks, and the length of time during which they have been subjected to the comminuting forces. If we take a geological map of the British Islands and turn to the districts coloured as granitic, we shall find them largely covered with a thin cold clayey soil derived from the decom- position of the subjacent granite. Ordinary granite is com- posed of quartz, some variety of felspar, and mica ; and it is the felspar (silicates of alumina, with minor proportions of soda, potash, lime, and iron) which mainly yield this poor moorland covering, the sterility of which is aggravated by its general high elevation, whitish colour, and the impervious nature of the rock on which it rests. We say whitish colour, for, area for area, white soils take in less heat than dark-coloured ones the former reflecting and the latter absorbing the solar rays. If we turn, on the other hand, to the tracts coloured Trappean, we will find them covered, for the most part, with a dark-coloured, dry, crumbling soil, noted for its fertility and certainty of cropping. This arises from the disintegration of the softer trap-tuffs, amygdaloids, and wackes, and consists, according to the analyses of the late Professor Johnston, of silica, alumina, and lime, with varying proportions of soda, potash, and iron ; its fertility and mellowness being augmented by its colour, which absorbs the sun's heat, and by the fissured structure of the rocks beneath, which carries off all superfluous moisture. In slaty and schistose tracts that is, those coloured Meta- morphic, Cambrian, and Silurian, we find that where these rocks are not masked by diluvial drifts, they have weathered into thin clayey soils of indifferent fertility, partly owing to their elevation, and partly to their retentive texture green nutritive pastures occurring, as in the southern uplands of Scotland, only where the high inclination of the beds, with their slaty structure, affords a ready and efficient natural drainage. The soft, sandy, and marly strata of the New Red Sandstone break up into a dry fertile soil, especially suited for barley and green crops ; while the clayey and marly beds weather down to a stiff retentive clay, like that of Cheshire, much better adapted for permanent pasture than for the varied requirements of corn culture. Over the Lias and Oolite, consisting of alter- nations of calcareous and argillaceous strata, we have those noticeable belts of dry, rubbly, and stiff clayey soils, which 36 GEOLOGY AND AGRICULTURE. characterise a large portion of England, from Yorkshire on the north-east to Dorset and Somerset on the south-west the calcareous freestones forming the drier ridges, and the clays the moister valleys. In the south-east of England, the tracts coloured as Hastings sands, Weald Clay, Greensand, Gault, Chalk, and London Clay, are respectively characterised by thin, light sandy, stiff clayey, or dry calcareous soils the direct results of the disintegration of their immediately underlying rocks. Indeed, this connec- tion between the soils and subjacent rock-formations is best seen along the Secondary and Tertiary tracts of England that is, from the New Red Sandstone upwards through the Lias, Oolite, Wealden, Chalk, and Eocene deposits of the London and Hampshire basins. No doubt sporadic patches of diluvial drifts occur here and there to break the connection, but, generally speaking, the soils, modes of culture, crops (wheat, barley, beans, hops), coincide with and are favoured by the lithological belts, as depicted on the geological maps of the country. Nor do these lithological areas influence alone the white and green crops of the husbandman ; they are equally, if not still more, operative in the growth and value of the timber trees of the forester. The firs and larches which thrive so magnificently on the decomposed mica-schists of the Scottish Highlands would be but poor stunted sticks on the thin cold clays of the granite ; while the oaks, and elms, and orchard- growths which flourish on the marly clays of the New Red Sandstone, would become stunted and gnarled if transferred to the drier and scantier soils of the Chalk and Carboniferous limestone. Soils of Transport. When we turn to the soils of transport we find them of a much more miscellaneous character, and occupying much more extensive and unbroken areas. Some consist of river- drifts shingly gravel, sand, or alluvium ; others of old lake- sites peaty earth, clays, sands ; some of old estuary beds tenacious clays and silts ; others, again, of wind-blown sands and sand-dunes ; and many of glacial drifts sand, shingly gravels, and stiff bouldery clays. These may of themselves form the arable soils, or they may constitute the subsoils, and be overlaid by a coating of less or greater thickness, partly derived from their own disintegration, augmented by the growth and decay of plants, and partly formed by the plough and repeated cultivation. But whatever be their nature and SOILS AND SUBSOILS. 37 origin, they are little, if at all, influenced by the subjacent rock-formations, and have to be studied and treated by them- selves. Over the Old Red Sandstone, the Carboniferous and Permian systems, which consist mainly of sandstones, shales, and clays, there is in most parts of the British Islands a thick coating of diluvial or bouldery clay, very stiff, retentive, and sterile. Much of this boulder-clay has been brought from a distance by ice-action; but the major portion, perhaps, is but the ground-up material of the formations on which it rests, hence its reddish tints on Old Red tracts, and its dark-blue colour over the Coal-formation. In many of our larger plains Strathmore and Strathearn, for example there is a very miscellaneous assortment of drifts sands, gravels, shingly debris, and boulder-clays ; and in the lower and wetter por- tions, peat-earths and alluvia, the remains of silted-up lakes, or of lakes still in process of obliteration. In our lower carses and valleys Carses of Cowrie, Falkirk, and along the Humber there are large expanses of soft plastic clays (old estuary bottoms) of great fertility, but of difficult and uncertain cultiva- tion ; while such tracts as the Fens of Lincoln, Romney Marsh, and the like, are chiefly marine silts and marsh growths. Sand-dunes, or link-lands along the sea-shores, and inland marshes, also occupy extensive tracts ; and, indeed, by far the larger area of these islands consists of subsoils and surface soils, having no connection with the rocks on which they rest, and little, if at all, influenced by their proximity. These soils of transport must therefore be studied and treated by them- selves, whether as regards fertile and permanent admixture, draining, or manuring. Along with these soils of transport may be classed some of organic accumulations, such as peat-moss and bog-earths, which have no geological connection with the subsoils or rocks on which they repose. Such accumulations are often of great thickness, and rest on old estuary and lake silts, on sands, and on clays of totally different origin, and indeed, as in the case of Blair-Drummond, the peaty stratum may be altogether removed in order to expose the finer and more fertile clay that lies below. Fertile Admixture of Soils. It must be obvious that soils varying so much in their origin, composition, and texture cannot be all alike culturable and fertile ; and hence to correct the one by admixture with the other, to render this one more friable and that more compact, to improve this one by drainage and that by manuring, is the sum and substance of judicious and successful farming. 38 GEOLOGY AND AGRICULTURE. Taking a good loam (an admixture of clay, sand, and organic matter) as the type of productiveness, we find some soils too sandy and light, and others too clayey and heavy. Sandy soils, though active, soon become exhausted, and are apt to be parched in dry seasons ; and clayey soils, though often rich and absorbent of ammonia from the atmosphere, are apt, in wet seasons, to become water-logged and unworkable. It is thus that some soils are too cohesive, others not cohesive enough; some deficient in one element, and others having that element in excess. It is the duty of the skilful agri- culturist, therefore, to correct these deficiencies by admixture, and to bring his soils as near as he can to the normal con- dition of easy cultivation and fertility. If we take an estate of some extent, for example, and after careful pitting and examination map out its soils and subsoils, and find that some of its fields consist of stiff retentive clay rest- ing on the rubbly outcrops of the strata below, others of thinnish loam resting on a subsoil of sandy clay, some in the hollows and along the streams of soft peaty earth, and the remainder skirt- ing the sea-shore of dry shelly sand, the question arises How are we to effect a permanent improvement of these various soils by drainage and admixture ? The cold retentive clays, on which insolation is spent in evaporating moisture before it can impart any warmth, may be dried by draining, and subse- quently cut up and rendered friable by admixture with the shelly sand ; and such clayey soils may also be improved by burning, which not only renders them freer, but converts their potash from an insoluble to a soluble state. The thinnish loam might be deepened by subsoiling, provided there was nothing deleterious in the clayey subsoil ; the soft spongy peat-earths which throw out their seeds and roots after frosts might be im- proved, as every one knows, by an admixture of the clays ; and the loose dry sands can be readily compacted and rendered fertile by a good addition of clay, as we have seen near the estuary of the Eden in Fife, where sands, almost useless as sheep-runs, have been converted into profitable grain-fields by admixture with the soft red brick-clays which abound in that locality. We have taken an imaginary instance \ but, whatever the example, there are few estates which have not their fertile and unfertile portions, and all of which might be permanently improved by such admixture of soils, and these admixtures often lying within their own boundaries. We refer to lands at moderate elevation, and naturally fitted for the plough; for there are wide expanses in Britain which should never be broken up from their natural pasture, unless they could be put SOILS AND SUBSOILS. 39 under glass a provision which fluent expatiators on the conversion of waste lands forget to make allowance for in their Utopian speculations. For such admixtures as those to which we have referred, a geological knowledge of the district is indispensable ; and be it observed that fertile admixture of soils is a permanent improvement a creation, as it were, of new soils and not like manuring, which is a mere temporary expedient, soon losing its effect and requiring to be repeated at every rotation. Draining. The same may be said of draining, and there is much in drain- ing that depends on the geology superficial and lithological of the district in which it is to be effected. The main ob- ject of draining is to get rid of superfluous water, thereby rendering the soil drier and more absorbent of the sun's heat, more friable and opener in texture for the admission of air and rain, which prevent the generation of deleterious acids, more accessible to the tender permeating rootlets of the crop, and likewise more easy and certain of cultivation. Before excavat- ing the drains, it is always worth inquiring whether the wet is retained in the surface soil by an impermeable underlying " pan," which, if broken up by the subsoil plough, would be sufficient to let off the superfluous moisture through the under- lying beds ; or whether the thin clayey soil would not require all the moisture if it were cut up and deepened by sandy ad- mixture ? Again, in some very level tracts where sufficient fall is difficult to be obtained, it is also worth trying the nature of the subjacent beds to see whether they might be porous enough to receive and carry off the discharge of the drains. Under some morasses there have been found beds of open quartzose sand, which when dug down to were sufficient to carry off all the drainage water ; and in the Wealden and Chalk dis- tricts it is not unusual to find in the porous Kentish Rag and Chalk, which lie below, a sufficient outlet for the drainage of the superincumbent heavy clays and loams.* This property * "Owing to the greater part of the farm (Hall Farm, near Sevenoaks, Kent) being naturally dry, very little drain ing has been required, but that little has been effected by the following rather ingenious method : Wells have been sunk to the depth of from twenty to thirty feet, at which distance from the sur- face the Kentish Rag or stone is usually found. These wells receive the water from the different drains which empty into them, and as the Kentish Rag is of great extent and thickness, and very porous, the wells are capable of receiv- ing any quantity of water which may issue from the drains. Part of Knole Park has been drained upon the same principle, and could have been drained in no other way without a very great expense, as from the formation of the sur- face much difficulty would have been found in obtaining a fall." Jour, of Roy. Agric. Soc., vol. viii. 4O GEOLOGY AND AGRICULTURE. of taking away surface water is possessed by all rocks having sufficient porosity, and especially by sands and gravels, chalks and limestones, absorbent sandstones and fissured trap-rocks. As draining, when thoroughly executed, should be viewed as a permanent improvement, every precaution should be taken to ascertain the nature of the soil and subsoil to be operated upon, to fix upon proper depths so as at once to deepen the soil, and not to carry off the dissolved manures, to see whether there be surface stones on the estate for the rilling of the drains, or whether these might be rendered more efficient by covering the tile-pipes by stones which have otherwise to be got rid of. The sole object of admixture and drainage is to render soils at once more easy of cultivation, and more certain and abund- ant in their productiveness. The qualifications of a pro- ductive soil are thus succinctly epitomised by Professor Ansted : " It should be composed of nearly equal parts of three earths sand, clay, and lime ; it should contain a certain quantity of decomposing vegetable and animal matter; it should imbibe moisture, and give it back to the air without much difficulty ; it should have depth sufficient to permit the roots of plants to sink and extend without coming to rock, to water, or to some injurious earth ; the subsoil should be moderately porous, but not too much so : and, in case of need, the subsoil should be able to improve the soil by ad- mixture with it. The proper proportion of the various earths may vary from 50 to 70 per cent of silicious matter, 20 to 40 per cent of clay, and 10 to 20 per cent of calcareous matter. According as the climate is wet or dry, the soil should be friable or porous, or adhesive and retentive, and the best soil is that which, in long drought, is never very dry, and in the wettest seasons does not become choked and soured with water." To these remarks may be added those of M. Schiibler (Jour. Roy. Agric. Soc.) : " The more an earth weighs, the greater also is its power of retaining heat; the darker its colour, and the smaller its power of containing water, the more quickly and strongly will, it be heated by the sun's rays; the greater its power of containing water, the more has it in general the power also of absorbing moisture when in a dry, and oxygen when in a damp state, from the atmosphere and the slower it usually is to become dry, especially when endued with a high degree of consistency; lastly, the greater the power of containing water, and the greater the consistency of a soil, the colder and wetter, of course, will that soil be, as well as the stiffer to work either in a wet or dry state." MINERAL MANURES. 41 II. MINERAL MANURES. Under this head we advert to those manurial substances which are obtained from the crust of the earth, and which are spoken of as mineral, in contradistinction to farmyard manure, nightsoil, shambles-offal, and the like, which are of organic origin, and result from the decay, secretions, and exuviae of plants and animals. These mineral manures play an important part in modern agriculture, both in top-dressing for pastures, and as feeders and stimulants to grain and green crops. Though generally spoken of as " mineral," most of them (peat, marl, chalk, coprolites, osite, guano, &c.) owe their origin to organic agency, but are now separated from the " organic " because they are more or less mineralised, and form component portions of the rocky crust. However much the soils of a farm may be benefited by admixture and drainage, they cannot continue to be cropped without the application of manures. Every crop, as may be seen by an analysis of its ashes, takes so much mineral matter from the soil on which it grew. In course of time this mineral matter will become exhausted, and the plant, deprived of its appropriate nourishment, will cease to flourish. To maintain the standard of fertility is the great object of manuring ; and whatever will restore to the soil in a state of solubility what the plant has withdrawn for plants can take no food in by their roots and spongeoles, save in solution becomes a manure. The manures obtained from the mineral kingdom are very numerous, but the most important and abundant are those of a carbonaceous, calcareous, and saline nature, yielding to the growing plant carbon, silica, lime, soda, potash, and other essential ingredients. Different crops require, of course, different manures, and what may start turnips into luxuriant growth may have com- paratively little effect upon a field of clover. The mode and amount of application belong to the art of husbandry ; geo- logy deals only with the nature, occurrence, and abundance of the manurial substance. Numerous experiments, however, have been made with the mineral manures, and the special results recorded in the Journal of the Royal Agricultural Society of England, and in the Transactions of the Highland and Agricultural Society of Scotland, to both of which the farming reader may refer with advantage. 42 GEOLOGY AND AGRICULTURE. Carbonaceous Manures. First among these mineral manures we may notice feat, which occurs largely as a surface accumulation in most situa- tions in all temperate and coldly-temperate countries. In our own country, especially in Scotland, Ireland, and the northern counties of England, it can be obtained in inexhaustible supplies. It is strictly of vegetable origin, contains little earthy matter, is found from the " turf" now growing to the old compact "peat," 20 or 30 feet in depth, and often covering areas thousands of acres in extent. When dug up and exposed to the weather, it crumbles into a dark pulveru- lent mass, and in this state, either alone or in . admixture with quicklime, has been applied with beneficial results to stiff loams and clays. It has been also fermented in admixture with farmyard manure, thereby not only increasing the mass, but absorbing and fixing the ammonia which escapes during fermentation. And in many cases it has been charred by combustion in smothered heaps, and the dry ashes applied with excellent effect to soils deficient in vegetable or carbona- ceous matter. According to Professor Johnston, " charred peat forms, likewise, an excellent absorbent for the liquids of the farmyard and the stable, and for drying up dissolved bones." Coal-dust or " slack " is sometimes spread on cold stiff clays, but with little effect, we presume, beyond that of cutting them up and rendering them more friable. Coal-asJies and the light porous coke from shale retorts, tell with better effect ; and soot, which is merely charcoal in a very fine state of sub- division, is often employed with wonderful results as a top- dressing to pastures, as well as to grain crops. Its fertilising properties are mainly due to the ammonia, sulphate of lime, nitric acid, and certain other ingredients which it contains. Calcareous Manures. Marl, which occurs in lakes, or is found at or near the sur- face, in bogs and morasses, the sites of obliterated lakes, is a soft earthy carbonate of lime, resulting from the shells of fresh- water molluscs (paludina, limnea, &c.) and other minute animal organisms. It generally occurs in layers and patches, from one to several feet in thickness : and when the shelly matter predominates, it is spoken of as shell-marl ; where the silty matter prevails, as day-marl. It is now seldom used ; but about the beginning of the present century was largely dug or dredged up, and applied in a raw state as a top-dress- ing to pastures, or as a corrective to clayey and peaty soils. MINERAL MANURES. 43 Another calcareous substance often applied with beneficial results to stiff clayey soils is the shell-sand (shelly, coralline, and other limey debris) which occurs largely along certain portions of our sea-coast. Consisting, for the most part, of carbonate of lime, with a certain amount of the phosphate, it not only acts as a break er-up of the stiff-textured clays, but from its gradual solution by the carbonated rain-water supplies to the soil an important element of fertility. Con- sidering the vast amount of this material which lies scattered along our shores, and which is easily manipulated, it looks like ignorant neglect on the part of our farmers that so little of it should be employed. In the Report on the Geo- logy of Devon, Cornwall, and Somerset (1839), ft is stated that, in 1811, Mr Worgan estimated the cost of the land car- riage of this sand in Cornwall at more than ^30,000 per annum. Large quantities are obtained at the Durbar Sands, in Padstow Harbour, the annual amount estimated at 100,000 tons. It has been calculated that 5,600,000 cubic feet of sand, chiefly composed of comminuted sea-shells, are annually taken from the coasts of Cornwall and Devon, and spread over the land in the interior as a mineral manure. It is also applied in some of the Western Islands, where the shores are thickly fringed with it, with beneficial effect to hill pastures and peaty soils ; but notwithstanding these facts and figures, the substance, considering its abundance and obvious utility, is strangely neglected. It abounds on the shores of France, and, according to M. Burat, is highly valued as a cheap and efficient manure, as well as an improver of stiff clayey soils. Like marl and shell-sand, the upper Chalk of the south of England (a soft earthy carbonate of lime) is sometimes broken down and applied to clayey soils and pastures. Applied in this way, at the rate of 30 and 40 loads an acre, it acts chemically as a manure, in rendering the soil richer, and mechanically, in ren- dering it lighter and more friable. Though now a lime-rock of great extent and several hundred feet in thickness, chalk is mainly of organic origin about 80 per cent of its mass being composed of the minute shields of foraminifera, similar to those now forming the calcareous ooze of the mid- Atlantic. Gypsum, or sulphate of lime, is applied in a similar way to grass-lands in this country, at the rate of 2 or 3 cwt. per acre ; but in Germany and the United States of America it is largely used in general husbandry, and with marked effect on crops of maize, pea, bean, and clover. Gypsum occurs crystallised and massive, in various formations ; but the most extensive beds are found in connection with rock-salt in the New Red Sand- 44 GEOLOGY AND AGRICULTURE. stone, and alternating with the clays and marls of Tertiary basins. In Britain abundant supplies can be obtained in Chester, Nottinghamshire, Derbyshire, Westmoreland, and other localities ; and not a little of that which is raised finds its way to the artificial manure factories. But while the carbonates of lime (marl, shells, and chalk) are applied in the raw, mild, or uncaustic condition, limestone in general is much more extensively used in the caustic or quicklime state. In this condition it is extensively used, not only as a top-dressing, but incorporated in the soil as a feeder, dissolver, and stimulant its effects being partly mechanical and partly chemical. " They are mechanical," according to Pro- fessor Johnston " as by slaking, the burned, lime can be re- duced to a much finer and more bulky powder than the limestone could be by any mechanical means ; and they are chemical, inasmuch as by burning the lime is brought into a more active and caustic state, and is, at the same time, mixed with variable proportions of sulphate and silicate of lime (evolved in the kiln) which may render it more useful to the growing crops/' The limestones are largely developed in the British Islands, and occur in all the geological systems Metamorphic, Silurian, Devonian, Carboniferous, Permian (Magnesian Limestone), Oolitic, and Cretaceous. There are few districts that cannot command a supply within their own area, or, at all events, at comparatively little expense from some contiguous area. (See Chapters V. and VI.) Besides the carbonates and sulphates of lime, the phosphates are also extensively used and highly valued as mineral manures. A crystallised variety under the name of apatite (56 lime, 44 phosphoric acid) is obtained from veins in the older rocks ; is of various shades of colour, white, yellowish white, and greenish white ; stands 5 in the scale of hardness, and has a specific gravity of 3 or 3.25. It occurs in various countries, Norway, Spain, Bohemia, Switzerland, France, &c., and is often accompanied by a massive variety, which is known as phosphorite. This phosphorite is the more abundant product, and consists of phosphate of lime 81, fluate of lime 14, with iron oxide and silica. These hard phosphates, of which there are several varieties, require expensive mining and reduction, and hence they have given way, in a great degree, to the phosphatic nodules and concretions of the Greensands and Tertiary formations. Phosphatic nodules, coprolites, or " cops" as they are familiarly termed, are occasionally concretions round bones and true coprolites or fossil excrement ; but, generally speaking, they are MINERAL MANURES. 45 mere nodular or concretionary masses of a soft and earthy texture. They are found in the Greensand and Crag forma- tions of England, and also in the Greensands of France, in layers and in sporadic deposits, from a few inches to several feet in thickness, and when moderately pure contain about 50 per cent of phosphate of lime. Well-cleaned examples from Cambridgeshire have been found to yield phosphates 61, car- bonates 28, insoluble silicious matter 7, and water, with traces of organic matters, 4. Their dissemination in the Crag and Greensand is rather uncertain; but ;8o, ;ioo, and even it is said as much as ^400 per acre has been paid for the right to dig and remove them from the estate. According to Hunt's 1 Mineral Statistics/ the amount raised in 1872 was estimated at 35,000 tons, value ^50,000. Similar deposits of a much more extensive nature occur in the Tertiary formations of the Caro- linas, New Jersey, and Georgia, and are largely used in the United States of America, as well as imported into Britain for the manufacture of artificial manures. Picked, crushed, and treated with sulphuric acid (and variously mixed with other substances), they form the "superphosphates" of commerce every manufacturer adopting his own treatment and pro- portions of admixture. Whatever the admixture, the great object of the sulphuric acid is to convert a considerable part of the insoluble earthy phosphate of lime into sulphate and soluble superphosphate. Plants take in no food save in a state of solution, and the main value of a manure (other things being equal) is its capability of being dissolved by the moisture of the soil according to the requirements of the crop to which it is applied. What is termed osite, Sombrero guano, or Sombrerite, is another phosphate of lime used also in the manufacture of artificial manures. It is obtained from Sombrero, one of the West India Islands an islet about two and a half miles long, from a half to three-fourths of a mile wide, and not more 'than 20 or 30 feet above the level of the sea. The islet is entirely composed of this substance, which consists of a breccia of bones of turtles and other marine vertebrata, coral debris, &c., collected when the area was a shallow shoal, and before its elevation above the water. Since its elevation the rains have carried down through the mass the dissolved droppings of birds (guano), and cemented the whole into a compact mass of valuable phosphate. The true guano (huanu of the Peruvians), though of animal origin, has undergone so much alteration by internal chemical change, and occurs in such masses, that it may, without much 4 6 GEOLOGY AND AGRICULTURE. error, be treated as a mineral manure. It consists mainly of the droppings of countless sea-fowl, intermingled with their skeletons and eggs, the decomposed bodies and bones of fishes, seals, and other marine creatures frequenting the islands on which it is deposited. Though obtained principally from the rocks and islets that stud the Bolivian and Peruvian coasts, it accumulates in all rainless regions the drier the latitude the thicker and richer the deposit. On some of these islets it is found in great thickness (40, 60, 80, and in some places, according, to Dr Scherzer, 120 feet, and, considering its necessarily slow accumulation, must be of vast antiquity. The digging of the deposits and the frequency of modern shipping has greatly disturbed the birds, and much less is now deposited than in former times. About five-and-twenty years ago considerable quantities were obtained from Ichaboe, and other places on the west coast of Africa ; but as absolute dryness is necessary to the preservation of the ammoniacal salts, which constitute the chief value of guano, these supplies brought little more than half the price of the Peruvian, and we believe are now entirely exhausted. The amount imported into Britain from Peru, since 1844, is estimated at five and a half million tons, valued at sixty-four millions sterling ; but this rate of importation cannot long continue for, according to the estimate of the British Consul at Callao in 1873, the whole of the exportable guano which Peru then possessed did not much exceed three million tons. The following analyses, from Johnston's 'Agricultural Chemistry,' show the relative composition of American and African guanos : Peruvian. Bolivian. Ichaboe. Saldanha. Water iq.OQ 6.91 16.71 iS.QS Organic matter containing am- ) monia f 53- *7 55-52 46.61 22.14 Common salt and sulphate of) 4.63 6. 3 i 12.92 5.78 Carbonate of lime, .... Phosphate of lime and mag- ) nesia, j 4.18 23.54 3.87 25.68 0.27 22.40 1.49 50.22 Sand, . I> 39 1.71 0.52 2.02 Saline Manures. Besides these calcareous minerals and guanos, a consider- able number of saline substances have recently been employed MINERAL MANURES. 47 with wonderful effect, both as top-dressings and as incorpor- ated manures. The chief of these are sulphate of ammonia, carbonates of potash and soda, nitrates of potash and soda, sulphate of potash, common salt, sulphate of soda, silicates of soda and potash, and sulphate of magnesia. Most of these are manufactured artificially, as sulphate of ammonia, for ex- ample, from the ammoniacal liquor. of gas and paraffin oil works; but many also occur in a crude or impure state in deposits often of considerable magnitude. In and around salt- lakes like those of Central Asia, along dried -up lakes and deserts like those of Asia and Africa, and over extensive reaches like the salinas of South America, these salts occur in abundance, and constitute important articles of commerce. The desiccated lakes of Central Asia have been described by various travellers as flat expanses, covered during the dry season with white efflorescences of various salts, from a few inches to 2 or 3 feet in thickness, and over which their horses had to pass, treading up to the knees among crackling crystals of great beauty and purity. Mr Shaw, in his recent travels in Tartary, rode through desiccated lake-sites, covered with a thin crust of sandy soil, but consisting beneath of beds of common salt, and salts of soda and potash, varying from i to 3 feet in depth, and often of almost transparent purity. The salinas of South America, which at present yield our main supplies, are described as superficial deposits, occupying extensive plains on the Pacific, or rainless side of the Andes, and usually covered with a white saline efflorescence or crys- talline incrustation. They occur at all elevations, from a few feet to several thousand feet above the sea-level, and are evidently the remains of old sea-reaches and lagoons that have been desiccated by the upheaval of the land. They ex- tend for about 600 miles north and south, but find their great- est development between latitudes 19 and 25 south, and at distances varying from 10 to 40 miles inland. The usual salts occurring in these salinas, as in those near Iquique and the desert of Atacama, are common salt or muriate of soda, sulphate of magnesia, sulphate of soda, sulphate of soda and lime, soda -alum, magnesia - alum, gypsum, anhydrite, along with chloride of calcium, iodide arid bromide of sodium, car- bonate and nitrate of soda, and in some places borate of lime and borax. The saline plain of Taramugal, for example, which is 3000 feet above the sea-level, consists, in some places of many feet in thickness, of sand indurated with salt, in others of soft sand with crystals of nitrate, and occasionally of true caleches of concreted soda and stony debris. These saline 48 GEOLOGY AND AGRICULTURE. sands and gravels are dug and lixiviated on the spot, the liquor evaporated, and the crude salts exported at the rate of many thousand tons per annum. We have said nothing of artificial manures, whose name is legion, but restricted our notice chiefly to manurial substances which occur native in the crust of the earth. No doubt these substances enter largely into the artificial manures of com- merce; but other substances of an organic nature are also employed, taking the manufacture more under the head of Chemical Technology than of Applied Geology. Indeed it is often difficult to say what enters into the composition of many of these artificial manures ashes, peat-mould, sawdust, gyp- sum, chalk, salt, sand, loam, and other substances still more worthless and objectionable than the worst of these. In the preceding paragraphs we have endeavoured to explain, as fully as our limits will permit, the relations that subsist be- tween Geology and Agriculture. Those refer to the soils upon which the farmer has to operate, whether they be soils of dis- integration, resulting from and directly affected by the rocks on which they rest or soils of transport, which have been weathered and wasted from distant rocks and laid down by various agencies in the situations they now occupy. They refer also to the subsoils on which the arable soils rest, and the influence these may exert on their drainage, texture, and fertility. Much of the agricultural surface of Britain consists of what the farmer terms " made soils " soils reclaimed from stony bouldery wastes, heathy, peaty moorlands, and plashy swamps and morasses, by blasting and removal of boulders, by turfing and burning, and by draining. But whether re- claimed or natural, soils are not all alike fertile, some being too sandy, too clayey, too peaty, or too calcareous ; and the question arises, How far their defects may be remedied by admixture with other soils, so as at once to impart to them the necessary composition and texture? Besides fertile admix- ture, there also arises the question of drainage, by which the superfluous moisture may be got rid of most effectually, and at the cheapest rate, so as to render the soil drier and mel- lower, and more easy of cultivation, more friable, and thereby more permeable by air and moisture, and deeper and softer, that the crops may readily extend their rootlets in search of the nourishment they require. As this nourishment or manure is largely obtained from the mineral kingdom, it becomes necessary, in the next place, to advert to the more important of the mineral manures treating of their geological nature, MINERAL MANURES. 49 their abundance, and the facilities with which they can be obtained. Whether carbonaceous, calcareous, or saline, these mineral manures are yearly assuming a greater importance ; hence the value of an intelligent acquaintance with them to the practical agriculturist. Considering, therefore, the na ture of soils and subsoils, their composition, texture, and relations to the subjacent rocks ; and considering also the im- portance of drainage, and the application of mineral manures all of which involve some acquaintance with the materials and structure of the earth the relations of Geology to Agri- culture must be sufficiently obvious and deserving of study alike by the landlord and farmer. Works which may be consulted. Johnston's 'Elements of Agricultural Chemistry and Geology;' Stephens's ' Book of the Farm ; ' Burn's ' Soils, Manures, and Crops ' Weale's Series; Liebig's 'Agricultural Chemistry;' 'Burat's Geologic Ap- pliquee;' ' Journal of the Royal Agricultural Society ;' 'Transactions of the Highland and Agricultural Society.' IV. GEOLOGY AND LAND VALUATION. EVERY landed estate has a twofold value one superficial or agricultural, and depending on the nature of the soil and climate above, another underlying or mineral, and depending on the nature and abundance of the rocks and minerals be- low. The surface value will vary according as the soil and situation are fitted for general husbandry, for pasture, for forestry, or for sporting purposes. Land valueless for grain- growing may be valuable for pasture, and wide expanses un- suited for either, may bring large prices as game moors and deer forests. Fancy prices may also be given for certain estates, the adjuncts of scenery wood and water, dell and dingle, cliff and crag conferring on them an adventitious value; but, generally speaking, the richness of the soil, the geniality of the climate, good roads, and access to markets, are the conditions which determine the price to be paid for the mere land-surface. We here refer to country estates in general, and not to those in the proximity of towns, or con- tiguous to navigable rivers and harbours, which often bring fabulous prices for building-sites, ship-yards, factories, and other similar purposes. But beyond this superficial value there is a mineral one, and this will be regulated by the nature of the rocks and ores below, their abundance, the facility with which they can be obtained, and the prospect of continuous or increasing demand. In selling or in purchasing estates, this twofold value should always be held in view; and no factor or estate agent can do justice to his client who is incapable of estimating, or of pro- curing reliable estimates, at once of the capabilities above, and the resources that lie below. We have known estates sold for the mere agricultural value of their cold, clayey, and retentive soils, without taking into account the bands of ironstone and fire-clay which lay below, and which could have been readily estimated by a competent mineral surveyor, or by a little judi- cious outlay in trial by boring. We have known others sold LAND VALUATION: SURFACE VALUE. 51 much beyond their value, from the impression that they con- tained ores of copper and lead, because at certain spots there were traces of old trials for these metals. In either case thou- sands might have been gained and saved by proper precau- tions to arrive at some definite estimate of the nature and abundance of the minerals that lay below. I. SURFACE OR AGRICULTURAL VALUE. And first, of the surface value, and the mode of estimating it as far as geology is concerned. Having ascertained the nature of the climate, water-supply, condition of roads, access to markets, public burdens, and other accessories, a minute inspection of the soils should be made, their capability of im- provement by draining, and their correction by admixture. As stated in the preceding chapter, a map of the superficial accu- mulations of the district may be consulted with advantage, but this cannot supersede a detailed survey of the soils and sub- soils of the estate. One portion may consist of sands, another of peaty earth resting on clay, a third of stiff heavy loam, and a fourth of dry shingly soil resting on the subjacent rock. Are the sands calcareous or simply silicious? Can the heavy loam be rendered drier and lighter by draining and by admix- ture with the sands? Can the peaty earth be improved in quality and texture by admixture with the clay, or can the peaty surface be conveniently removed, as in the case of Blair- Drummond moss, and the clay be exposed as the agricultural surface? Again, as some soils are better suited for certain crops, some for grain, others for green crops some for pas- ture, and others for forest growth, a knowledge of these facts may enable one purchaser to offer a price with safety, which would simply stagger another who was incapable of such dis- cernment. These and similar considerations must be weighed and balanced before the value of any estate can be fairly determined; and for this purpose frequent pittings in the soils and subsoils should be made, and the nature of the material methodically ascertained. A few spadefuls to reach the subsoil is all that is required in such pittings ; and con- sidering the certainty they confer on the estimates of the valuator, it is astonishing that this mode of determination is not more extensively and systematically adopted. As the estate stands, it has a certain value which depends upon the rental received ; and to one purchaser ignorant of its capabilities, this may determine the price while to 52 GEOLOGY AND LAND VALUATION. another acquainted with all its facilities for improvement, a much larger sum may be given, and yet in the long-run it may be a cheap, and profitable purchase. The farmer in offering for a new farm is never altogether guided by its existing condition, but looks forward to how much it may be improved during the currency of his lease, by judicious outlay in draining, subsoiling, removal of surface stones, and the like ; knowing well that by these means he will not only increase the quantity and quality of its produce, but greatly diminish the cost of cultivation. And so it should be with the purchaser of an estate ; he must not be altogether guided by existing appearances, but should consider well how far the property contains within itself, or lies adjacent to, the ready means of permanent improvement. The grazier who gives ten pounds for a growing beast, and pays five for its pasture, may at the end of the season sell it for twenty ; and so the purchaser of landed property who gives twenty thousand, and judiciously expends five on its improvement, may in a few years raise its value to thirty thousand. The Landscape. Surface Amenity. Closely connected with the value of the land-surface, is the art of laying it out into fields, parks, and plantations, so as to enhance at once its value and amenity. Few arts require more skill, and observation of nature's aspects, than that of landscape-gardening, not only in improving features which an estate may already possess, but in bringing out new features by judicious planting and enclosing. A domain naturally regular and tame in surface, may be rendered more attractive by the disposition of its woods and the winding lines of its enclosures. Another, naturally more diversified by hill and vale, crag and dell, may have its charms doubly increased by the skilful introduction of wood and water. It is astonishing how much can be done by a little judicious planting and enclosure. A few clumps to break the monotony of a moor, a trail of ivy over a bald brow of rock, a few climbers to mask the face of an old stone quarry, or a sprinkling of shrubs to enliven the slopes of an ordinary road-cutting, will often produce an effect worth ten times the outlay. And as with the minor, so with the major features of a domain, the tamest may be improved by intelligent treatment. No doubt such dispositions depend very much upon the artistic tastes of the disposer; but there are certain geological connections between trees and soils, woods and crags, rocks and waterfalls, a knowledge of which cannot fail to be of use to the landscape-gardener. Nature MINERAL OR GEOLOGICAL VALUE. 53 does not lay down clumps and belts of wood at random, nor erect crags and cliffs where there can have been no producing cause ; and it is the study of these causes and associations which lies at the foundation of all successful imitation by art. Every rock granite, slate, limestone, trap, sandstone, chalk weathers after its own fashion, and presents its own distinc- tive aspects (Chap. II.) ; every soil has its own peculiar vegeta- tion ; and the whole success of landscape disposition depends upon an acquaintance with these peculiarities. But beyond the mere beautifying of the surface, in a cold and fickle climate like Britain, shelter is indispensable, and wherever woods can be disposed so as to secure both warmth and amenity, the value of an estate is substantially increased. II. MINERAL OR GEOLOGICAL VALUE. In addition to its surface or agricultural value, every estate has a mineral worth depending on the nature of the rocky substances that lie below. In some instances this value may arise from the superficial clays, sands, peats, marls, coprolitic deposits, and the like ; in others, from the sandstones, lime- stones, coals, ironstones, granites, and greenstones ; and in others, again, from the occurrence of metalliferous veins. From whatever source it may arise, it is evident that no approximate estimate can be formed without a competent mineral survey. It is true the maps of the Geological Survey, when completed, will be of vast service in Britain ; but even with these a more minute examination and report should be obtained. The sheets of the Government Survey contain the broad and general features of the geology of the country; but the details of any single estate, the thickening or thinning of its strata, their dips and dislocations, their quantity and quality, and the like, can only be approximated by a special investigation. Such a survey even when corroborated by trial - borings can generally be obtained at no great cost compared with the interests at issue ; and yet for want of this precaution, every year witnesses blunders in purchase as well as in sale. And if such a precaution be needed in an old and well-known country, much more is it needed in colonies and countries that have not been systematically explored. The mineral wealth of an estate, we have said, may arise from various sources. Its superficial sands may be fitted for mortar, for moulding purposes, or for glass-making : its surface clays may be adapted for brick and tile making, or even for 54 GEOLOGY AND LAND VALUATION. finer pottery uses ; while its peat-earths and bog-marls may all be of value, if not for sale, at least in the improvement of its other field -soils. These superficial accumulations are too much neglected. A good field of brick-clay in the neighbour- hood of a rising town may be worth thousands ; a small estate full of sand-hummocks in the suburbs of Edinburgh brought nearly as much to its proprietor for builders' sand as he paid for it ; while the excavations were filled up with shot-rubbish, and the original surface-soil restored. Again, there may be dykes and bosses of greenstone and basalt valuable as road- metal ; granites and sandstones suitable for building; lime- stones for mortar or for furnace flux ; and limestones unfitted for these purposes on account of their argillaceous nature, may be eminently useful for their hydraulicity. If an estate lies on the coal-formation, there is generally an effort made to estimate its mineral value ; and yet in this respect how much caution is necessary may be seen from the high prices that the cannels have recently brought, relatively to the price of other coals, from the yearly increasing demand for fire-clays, and also from the rapid utilisation of the bituminous shales, which in 1855 were of no account whatever, and are now, for the distillation of paraffine oil and other products, worth hundreds of thou- sands. Lastly, an estate may derive its value from the occur- rence of metalliferous veins and stream - drifts, and though these may have been worked and known, yet new values are constantly being attached to certain ores from their wider application in the arts, and their consequently increasing demand. It must be obvious, from what has been stated, that a careful estimate of the mineral value of an estate is a thing of prime importance alike to the seller and purchaser. Of course, one cannot always anticipate the utilisation of products which may now be lying waste and worthless, nor the increasing demand and price of substances which may now be of little value ; but seeing within the last quarter of a century the increase of fire- clay manufactures, the demand for mineral manures, for oil- shales, for gas or cannel coals, for iron ores, and, above all, the recent advances in the prices of ordinary coal, it were folly to part with estates without due consideration of their mineral resources. In a country like Britain, where the geological formations are so varied, and where the progress of invention is so rapid, one can never tell when disregarded products are to be utilised, or known ones increased in value; hence the necessity, in dealing with landed property, of stricter attention to their mineral resources whether these belong to MINERAL OR GEOLOGICAL VALUE. 55 the older rock-systems below, or to the superficial accumulations above. Compare the price of an estate in the Cleveland district of Yorkshire in 1853 with its value in 1874; estimate the worth of a poor moorland tract in Linlithgowshire in 1856 with its value (for oil-shales) at the present moment ; or the importance of a farm on the Greensand (with phosphate nodules) at these respective dates, and no further argument will be necessary to establish the advantage of having in every instance of sale or purchase a thorough investigation of the geological features and mineral resources of estates. To obviate the risk of parting with unknown wealth for no adequate equivalent, the minerals of an estate are sometimes reserved, and the mere surface or solum disposed of. This practice, while it guards the seller, not unfrequently becomes a source of extreme annoyance to the purchaser or his suc- cessors. It is true they have their surface damages for any roads or excavations that maybe made in quest of the minerals; but there is none for loss of amenity by smoking iron-heaps, brick-clamps, waste mounds, and other unsightly adjuncts, while very often a rough and troublesome population is brought to the vicinity, and poor-rates increased by their improvidence as well as by the dangers of their occupation. It is true, no one can tell when certain minerals are to rise in value, or when worthless substances are to be utilised; and it seems hard that through such utilisation estates sold twenty years ago may now be worth three times the money then paid; but in face of such contingencies, it seems better, on the whole, that sales and purchases of estates should be entire and abso- lute the sellers taking every precaution to have the highest price for their conjoint agricultural and mineral capabilities. Some mineral substances may fall into desuetude, and others may acquire new and unexpected values ; but, generally speak- ing, in a mechanical and manufacturing country like Britain, the tendency will be towards a greater consumption, and conse- quently towards increased demand and higher prices. Taking this view, the seller of a mineral estate is justified in seeking a higher price, and the purchaser, on the other hand, equally safe in offering it. The same remarks hold good with respect to mineral leases. A farm may be let for nineteen years, as is usual in Scotland, and yet at the end of the lease, if proper precautions have been taken as to cropping and rotation, the soil may be richer and more valuable ; but at the end of a mineral lease the materials removed are gone, and for ever. No landed proprietor, therefore, who studies his own interest or the in- 56 GEOLOGY AND LAND VALUATION. terest of his successors, should, in the increasing value of mineral produce in Britain, grant long leases ; and in such leases as he grants, should always stipulate for a lordship proportionate to the market price of the substances disposed of. Millionaire iron and coal masters would have been fewer in number had landowners been sufficiently provident in the leasing of their mines and minerals. In the preceding remarks we have restricted ourselves almost exclusively to the sale and purchase of estates in the British Islands, but the same precautions are equally necessary in the selection and purchase of land in our colonial possessions. It is not always fertile soil and surface amenity which should determine the settler's choice. The finest soil and situation, unless for town-lots, will never bring more than an average agricultural return ; while some poor and forbidding tract may contain within it inexhaustible stores of minerals and metals, which will continue to rise in demand and value the more the population increases and settles down to commercial enter- prise and industrial activity. A little geological knowledge, and a few months spent in prospecting along the sea-cliffs, up the river-banks, and over the rocky surfaces wherever these may be exposed, will always repay the colonial settler, even should he have to wait several years for the development of the mineral resources of the tract he has chosen. Nor does it require much geological skill to detect the presence of the more important minerals and metals. Coals and coaly shales soon reveal themselves in any section ; ironstones show them- selves by their oxidised or rusty surfaces, and are usually accompanied by springs or trickles of water leaving an ochrey deposit; limestones weather into whitish or whitish-brown surfaces, and are frequently accompanied by petrifying springs; copper ores show various tarnishes of green, reddish, or pavonine tints, and are accompanied by trickles having a strong styptic and coppery taste ; lead ore or galena, by its leaden-grey colour and cubical cleavage; antimony ore, by its lighter-grey colour and long radiating crystals ; while the metallic ores in general may be readily detected from stony minerals by their greater weight and metallic lustre in the fresh-made fracture. It should be obvious, from what has been said in the pre- ceding paragraphs, that every landed estate has a twofold value one depending on its superficial qualities and their susceptibility of improvement, proximity to roads, public bur- dens, and access to markets; and another arising from its MINERAL OR GEOLOGICAL VALUE. 57 mineral resources, their nature and abundance, facilities of winning them, and amount and continuance of demand, existing and prospective. In selling or in purchasing landed property, these values should be respectively taken into account, and no reasonable trouble or expense withheld in approximating their amount by careful and competent surveys. In such surveys some knowledge of geology is indispensable, whether relating to the soils and subsoils above, or to the minerals and metals below. Nor, when these respective values have been ascer- tained, should it ever be forgotten that they differ in this important essential namely, that while the superficial value is ever increasing by judicious treatment draining, trenching, planting, &c. the mineral value, by working, is ever diminish- ing, and in the end may be wholly extinguished. Than this, no fact can be more obvious, and yet it is too often disregarded in arranging for the interests of heirs and successors. Works which may be consulted. Brown's ' Book of the Landed Estate ; ' Lintern's ' Mineral Surveying and Valuing;' Hudson's ' Land Valuer's Assistant;' Donaldson 'On Landed Property.' V. GEOLOGY AND ARCHITECTURE. PART I. BUILDING AND DECORATIVE STONES. THE relations of Geology to Architecture are at once intimate and important All our building-stones, stones for internal decoration and sculpture, mortars and cements, concrete and artificial blocks, are obtained directly or indirectly from the crust of the earth. It is not merely shelter and defence that man seeks from his structures; he has aesthetic tastes, and hence beauty of colour and texture, and capability of being fashioned and combined for the production of general effect, become important properties in the architectural materials with which he has to deal. The stone suitable for the massive fortress may be unfitted for the lighter mansion, and the material adapted for the country villa might be unsightly in the city street ; while tints in keeping with the plain frontage of a ware- house might ill accord with the ornamental fretwork of a cathedral church. Besides, the stone that will endure under a dry and equable climate may waste and weather away under a humid one ; while that which will retain its colour and fresh- ness in the air of the country may get dingy and corroded under the carbonated atmosphere of a manufacturing town. Nor is it alone colour and texture and general durability that have to be studied ; the modes of bedding and tooling and dressing suited to different stones are also important elements for consideration, as what might tone down the colour in one, and mask the rough texture of another, might altogether be a disfigurement to a third. Again, toughness or resistance to strain and pressure is paramount in stones for lofty and heavy structures, the hardest texture not being always that which will endure the highest crushing power. Another consideration is the structure or natural masonry of the rock in the earth's crust whether it be thick-bedded, flaggy or slaty, tabular, jointed, or columnar as on this structure depends its capability of being raised in blocks of sufficient size for any special requirement. ARCHITECTURE: BUILDING-STONES. 59 These and many kindred considerations have to be taken into account by the architect and builder ; but so far as our present purpose is concerned, the lithology of the materials which they have most frequently to deal with may be arranged under the following heads: i. Building -Stones ; 2. Stones for Decoration and Sculpture ; 3. Limes, Mortars, and Cements ; and 4. Concretes and Artificial Stones. I. BUILDING-STONES. i In building-stones for edifices (other than those of docks, piers, and breakwaters, to be noticed under Civil Engineering, Chap. VII.), the main requisites are beauty of colour and texture, durability, and facility of being dressed and tooled. These qualities vary very much in different rocks, some freestones being of beautiful colour and texture, and very readily quarried and tooled, but far from durable; some granites and por- phyries extremely durable and of pleasing tints and lustre, but expensive in dressing ; and others, like some grey grits and greenstones, both durable and easily tooled, but very sombre and unsightly in colour. In noticing these and other varie- ties, we shall dwell mainly on the building-stones of our own islands, only touching, by way of illustration, on those of other countries, whether modern or ancient. And first of the Granites, Porphyries, Greenstones, Felstones, Basalts, and other kindred rocks of igneous origin and of pyro-crystalline or pyro-plastic texture. The Granites and Porphyries. The granites, which were early used, especially in Egypt, for monoliths and gigantic sculptures, form a numerous family, differing widely in colour, texture, and durability. In our own country they have come largely into use within the present century, both for structural and decorative purposes. This is chiefly owing to their durability and susceptibility of fine polish, but partly also to the invention of mechanical appliances by which their dressing can be facilitated. They differ con- siderably in their mineral composition, colour, texture, and facility of being raised in large blocks, but are all old igneous rocks, amorphous or tabular in structure, crystalline in texture, and occur chiefly associated with our most ancient hill-ranges, though in some regions they burst through strata as recent as the Jurassic and Cretaceous. Certain stratiform granites are regarded by some geologists as of metamorphic origin, but 60 GEOLOGY AND ARCHITECTURE. undoubtedly the great majority of the family are pyrogenous and eruptive ; and seeing that both igneous and aqueous rocks are alike subject to metamorphism, it matters little to the economic geologist whether the granites are old transformed sediments or altered eruptions. Their essential ingredients are quartz, felspar, mica, and hornblende, in varying proportions ; and their adventitious or accessory minerals are garnet, tourmaline, beryl, rock-crystal, and iron pyrites. By essential ingredients are meant those which constitute the mass of the rock ; by the adventitious are those which occur rarely, and generally in fissures and druses. There may be two or more felspars, and two or more micas, in the same granite, but generally the granites are described as fine-grained, medium-grained, or large-grained, or as porphyritic, when, like that of Shap in Westmoreland, they contain large and independent crystals of felspar scattered through the mass. The ultimate analysis of a granite may consist, for example, of 69 silica, 15 alumina, 6 oxide of iron, a trace of oxide of man- ganese, 2 lime, i magnesia, 4 potash, 3 soda, and i water ; but this gives no idea either of its colour, texture, resistance to pressure, or durability. The silica is partly free, partly in the felspar and mica the lime, soda, and potash partly in the felspar and partly in the mica and the magnesia in the mica. The colour, texture, susceptibility of polish, resistance to pres- sure, and durability, depend upon the size and arrangement of the several ingredients the granites most liable to decay being those containing an excess of lime, iron, or soda in the felspar and mica. Those containing large crystals of mica are unfitted, of course, for architectural purposes ; and the same may be said of varieties in which soda-felspar, and very deep- red (iron) felspar, predominate. The granites are quarried, for the most part, from hillsides and other rising grounds, have little or no superficial covering, are blasted for smaller purposes, but cut with wedge and mallet for larger blocks and monoliths. In most quarries the rock has a rudely-jointed or tabular structure, but in some instances it is massive, and capable of yielding blocks of large dimen- sions. Like other rocks, it can be squared and dressed with greater facility when newly raised a*nd in possession of its " quarry-water;" and this, according to the texture of the rock, may vary from 5 to i per cent of its weight. Some granites of open texture are capable of absorbing as much, it is said, as from 2 to 3 gallons per cubic yard, and those absorbing the most are the least to be relied upon for their durability. The specific gravity of ordinary granites ranges from 2.6 to 2.8 ; BUILDING-STONES. 6 1 a cubic foot weighs from 164 to 169 Ib. ; and from experi- ments on inch cubes, the crushing force varied, according to the texture and composition, from 3000 up to 13,000 Ib. The following are some of the best known and most esteemed varieties : Common Granite consists of quartz, felspar, and mica ; and, as the felspar may be whitish or reddish, and the mica black, brown, or silvery, is of various colours, of various textures, and is that which is most abundantly employed in ordinary archi- tecture. The granites of Aberdeenshire belong to this variety, whether grey, like that of Cove, Rubislaw, Dancing Cairn, and Tyrebagger ; reddish and warm-tinted, like that of Stirling-hill, near Peterhead ; bluish-grey and somewhat porphyritic, like that of Cairngall ; or white and largely granular, like that of New Pitsligo. Of this kind also are the greyish granites of Inverary and Oban in Argyle, the pink-tinted medium-grained granite of Mull, the softer greyish-white granites of Dalbeattie in Kirkcudbright and Creetown in Wigtownshire, the light-grey of Wicklow and Wexford in Ireland, the darker-grey of County Down, the rose-pink of Mount Sorel in Leicestershire, the whitish of Cornwall, the bluish-grey of Hay Tor in Devon, and the dark-blue of Jersey. When small or medium-grained, ordinary granite tools well, takes on a fine hammered surface or polish, stands any amount of pressure, and resists the action of the weather. The better buildings of Aberdeen, and por- tions of some of the public edifices of London, Dublin, Liver- pool, &c., may be taken as examples of its fitness for archi- tectural purposes. Without fine tooling, however, and merely rough-dressed and in large courses, it has by no means an at- tractive appearance. One objection to the granites and more to the granites than the syenites is, that they suffer severely from fire; a conflagration that scarcely affects a sandstone destroying altogether the surface and texture of a granite. Porphyritic Granite (as already explained) is the term applied to those varieties in which larger and distinct crystals of felspar are interspersed through the mass. These granites are more frequently used for decorative than for ordinary buildings, and some of them, when properly disposed, produce a very pleas- ing effect. The granite of Shap in Westmoreland, now coming largely into use, is one of the most beautiful, consisting in some portions of a reddish-brown, and in others of a light- brown base, with large interspersed crystals of flesh-coloured felspar. Some of the Dartmoor granites are also porphyritic, the base being of a whitish-grey colour, with large oblong crys- tals of whiter felspar the "horse-teeth" of the quarrymen. 62 GEOLOGY AND ARCHITECTURE. Most of the Galway granites, and that of the island of Arran- more, are also porphyritic, consisting of a greyish or greenish- grey base, with large imbedded crystals of reddish felspar. As decorative stones, many of the porphyritic granites are worthy of wider attention. Graphic Granite, found principally in veins, consists of quartz and felspar arranged in lamellar form, and is so called from the quartz appearing in the cross fracture like cuneiform letters. It is found in Banffshire, in the Urals, and other localities, but from its rarity and small size is used only for minor ornaments. Generally speaking, the granites are too expensive for the majority of buildings, except in towns (Aberdeen) where they are the only available rocks ; and are employed more as ac- cessory dressings and decorations, as will be seen under the second section of the present chapter. For bridges, piers, lighthouses, parapets, dock-gates, sea-walls, and similar heavy structures (see Civil Engineering), their hardness, toughness, and weight render them especially suitable ; and to these and street purposes the great bulk of the granite raised in the United Kingdom is at the present time applied. Syenite and Syenitic Granite are two names somewhat loosely employed by geologists. A true syenite (from Syene in Upper Egypt) is a binary admixture of felspar and horn- blende ; a syenitic granite, a compound of quartz, felspar, and hornblende, and not unfrequently of quartz, felspar, horn- blende, and mica. The syenitic granites are, on the whole, tougher and more compact than the ordinary granites, take on a fine polish, and are exceedingly durable. They occur less abundantly in nature ; but their rarer use most frequently arises from the darker tints imparted to them by the horn- blende. The Channel Islands, Mount Sorel in Leicestershire, Wales, Donegal, Argyleshire, and Skye, are localities where they occur in masses fit for economic employment The Porphyries form a numerous and very varied family of pyrogenous rocks. The term porphyry (Gr. porphyreos, red- dish purple) was originally applied to a rock from Upper Egypt, consisting of a reddish or reddish-brown felspathic base with thickly interspersed crystals of white-coloured felspar, and largely used for sculptural purposes. This term is now employed by geologists to denote any rock (whatever its colour) which contains imbedded crystals distinct from the main mass or matrix, though, properly speaking, it ought to be restricted to those having a felspathic base. BUILDING-STONES. 63 The porphyries generally occur as dykes and eruptive masses intersecting the older schists and slates, and are usually much fissured and jointed, and for this reason incapable of being raised in massive monoliths like the granites. In our own country they are found cutting through the Cambrian, Silurian, and Devonian rocks of Ireland, Wales, Devon, and Cornwall, the Lake District, the Southern Uplands and North- ern Highlands of Scotland. On the Continent, the old rocks of Scandinavia, of Germany, France, Italy, and Greece, are intersected by similar porphyries some of which are much prized for ornamental objects. Beautiful vases of large size (Museum of Economic Geology) are occasionally fashioned from the dark-coloured porphyries of Norway. Those found in the British Islands belong to the following two main varieties : The Q?iartziferous Porphyries, in which the matrix is a finely granular or micro-crystalline compound of quartz and felspar, with independent crystals of quartz and felspar thickly inter- spersed; and the Felstone Porphyries, in which the basis is a com- pact or pasty felspar, with independent crystals of felspar scat- tered throughout. Both varieties appear in many tints red, flesh-coloured, fawn-coloured, black, bluish-black, and bluish- green; and both varieties may contain, in subordinate quanti- ties, other crystals than those enumerated above. Some fine varieties, and fit for ornamental purposes, occur at Luxullian and Bodmin in Cornwall, in North Wales, at Lambay Isle off the east coast of Ireland, at Blair- Athole, Potarch on the Dee, and at Lucklaw in Fifeshire. Incapable of being raised in large blocks, they are polished only for minor ornaments their principal use in Britain being for causeway-stones and road- metal, for which their hardness and toughness render them specially suitable, as noticed under the chapter on Civil En- gineering. Though chiefly used for road -material, in some districts they are employed in the building of country man- sions, farmsteads, and walls ; and when properly dressed and coursed make a very fair structure (especially the fawn-coloured sorts), and are perfectly indestructible. Basalts, Greenstones, Felstones, &c. The basalts, greenstones or whinstones, felstones or clay- stones, constitute a numerous class of rocks ; and we employ these old and well-known names in preference to a number of recently imported Continental terms which refer to minute and unimportant distinctions, and by which no ordinary observer .could distinguish them in the field. They all belong to what 64 GEOLOGY AND ARCHITECTURE. are generally known as trappean or trap-rocks, and consist in the main of felspar, augite, hornblende, and hypersthene, with accidental enclosures of iron pyrites, olivine, and other rarer minerals. As rock-masses they occur in dykes, in eruptive bosses, in interstratified sheets, and intrusive insertions, among all the stratified systems, from the Cambrian to the Tertiary inclusive. Some of them, like the basalts and greenstones, are columnar or subcolumnar in structure (hence seldom capable of being raised in large monoliths) ; most of them are micro-crystalline in texture, and only the felstones and highly felspathic greenstones are pasty or compact. The specific gravity of these rocks varies from 2.4 to 2.9 or upwards; they weigh from 168 to 180 Ib. per cubic foot; resist a crushing power, according to their texture, from 20,000 to 30,000 Ib. on one-inch cubes ; and are generally little absorbent of water, say from 6 to 8 oz. per cubic foot. They are mostly dark-colouredblack, bluish-black, green- ish-black, and greyish-black in the basalts and greenstones, and only in the felstones fawn-coloured, reddish, or purplish. Their dingy colour is against them for street architecture ; and yet we have seen country mansions and cottages of well-coursed green- stone when relieved by white sandstone dressings rybats, sills, and lintels have a very pretty and pleasing effect. The ancient Egyptians and Hindoos occasionally used the finer-grained ba- salts (anamesites) for sculptural purposes, examples of which may be seen in several of our public museums. In our own country, basalts, greenstones, and felstones are mainly employed (see chapter on Civil Engineering) as road-materials, for which pur- pose they cannot be excelled. Closely allied to the basalts and greenstones, both in origin and composition, are the Lavas, of which, strictly speaking, we have no examples in the British Islands. In Italy, Auvergne, and the Rhine district, lavas of closer texture have been em- ployed in building; but their main use now, as informer years, has been materials for streets and roadways. The Slates and Schists. Intermediate between the igneous and sedimentary rocks stand the metamorphic slates and schists the clay-slates, chlorite-schists, mica-schists, and gneisses. These old rocks generally occur in a slaty or fissile state, and are better adapted for roofing, paving, and other slab-purposes, than for building ; and yet some of the compacter beds of the Silurian (the grey- wackes) make not a bad building-stone (Keswick, Kendal, Hawick, Galashiels), being flat-bedded, and easily squared and BUILDING-STONES. 65 jointed. Where obtainable, a frontage of this sort is greatly improved by light-coloured sandstone dressings. In some dis- tricts, where sandstones and limestones are scarce, the mica- schists, gneisses, and chlorite-schists are employed for building purposes ; but though tough and durable, they seldom produce anything like a satisfactory effect. As slabstones for linings, cisterns, pavements, and the like, the clay-slates, being easily planed and jointed, are very use- ful, but their chief value consists in their fitness for roofing purposes. From many districts (Bangor, Carnarvon, Llan- gollen, Portmadoc, &c.) in Wales ; from Delabole in Corn- wall ; Tavistock, Ashburton, Staverton, &c., in Devon ; from Ireleth, Coniston, Honister, Windermere, &c., in the Lake country; from Killaloe and Valencia in Ireland; and from Esdaile,, Ballachulish, and Birnam, in Scotland, slates of all sizes, thickness, colours, and durability can be obtained, and the modes in which they can be fashioned and arranged for architectural effect is one of their main recommendations. For thinness, lightness, and straightness the Welsh slates are unequalled, but the Irish and the Lake district varieties are harder, heavier, tougher, and more durable ; while for strength and solidity the Scotch are perhaps superior to either. Objec- tions are sometimes taken to Scotch and other slates contain- ing cubical iron-pyrites. It is true these occasionally weather out, leaving empty spaces or even holes in the slate ; but we have seen the cubes in a Ballachulish roof as fresh and glitter- ing after a century's exposure as the day they were first laid on. A good slate is. little absorbent of water, cuts freely but toughly, weighs from 160 to 180 Ib. per cubic foot, and should resist a crushing weight of from 20,000 to 25,000 Ib. A great deal of effect can be produced by the shaping and arrangement of roofing-slate ; and luckily for the architect, almost every colour - black, blue, green, red, purple, and creamy - white * is readily at his command. What are known as Tilestones are not slates in the lithologi- cal sense of the term, but merely thin -bedded flaggy sand- stones obtained from various systems the Old Red, Carbon- iferous, Permian, Oolite, and Wealden. In the high-pitched roofs of old castles and cathedrals some of these tilestones have a fine effect ; but their great weight, compared with that of clay-slate, is the chief objection to them on flat-roofed * Some years ago a cream-coloured variety of great beauty was discovered at Lethnot in Forfarshire, but the difficulty of bringing it into market has since caused the quarry to be abandoned. E 66 GEOLOGY AND ARCHITECTURE. modern structures. Their greater thickness, however, renders the interior of a house warmer in winter and cooler in summer than the ordinary Welsh slates, and this, in a fitful climate like Britain, is no mean recommendation. They are still used in some country districts Forfar, Dumfries, Westmoreland, West Riding, Gloucestershire, &c. ; the thinner splitting of the flags being effected by exposing them edgeways to the frosts of winter. Sandstones, Grits, Freestones. We come now to the truly sedimentary rocks, which differ widely from the pyrogenous and metamorphic, alike in mineral composition, structure, and texture. These include the sand- stones, flagstones, grits, and conglomerates, as well as the lime- stones, which, though often of organic origin, are still to a great extent sedimentary and stratified. The sandstones and grits constitute a numerous family, and as old shore-sediments, occur in almost every formation the Old Red, Carboniferous, New Red, Jurassic, and Wealden. They consist for the most part of grains of quartz consolidated by pressure, and cemented by silica, lime, or oxide of iron ; and frequently contain scales of mica, and not unfrequently carbonaceous particles scattered through the mass. They ap- pear in all colours white, black, grey, greenish-grey, red, brown, fawn-coloured, and yellow; and these colours some- times fade, and sometimes become intensified by exposure to the weather. In structure, some are thick-bedded and homo- geneous, and others thin-bedded, laminated, and flaggy : the former constitute the " post " or " liver-rock," the latter the " flagstones " and " pavement-beds " of the quarrier. In tex- ture they occur in every degree of fineness, from particles scarcely perceptible to the naked eye, to grains as large as a pea in other words, from fine-grained soft sandstones to coarse-grained silicious grits. As mixed rocks they consist of several ingredients, and, as the case may be, are spoken of as silicious, quartzose, micaceous, calcareous, argillaceous, ferruginous, bituminous, and carbonaceous. In chemical composition the sandstones vary extremely, and no two strata even from the same quarry will yield perhaps the same results. The following are analyses of some well-known varieties, as given in the Report of the Commissioners for the selection of stone for the new Houses of Parliament : Craigleith. Darley Dale. Heddon. Kenton. Mansfield. Silica, . . 98.3 96.40 ' 95.1 93.1 49-4 Carb. lime, . i.i 0.36 0.8 2.0 26.5 Carb. magnesia, o.o o.o o.o o.o 16. 1 Iron, alumina, 0.6 1.30 2.3 4.4 3.2 Water and loss, o.o 1.94 1.8 0.5 4.8 BUILDING-STONES. 6/ In specific gravity the sandstones and grits vary from 2 to 2.6; in weight per cubic foot, from 130 to 160 Ib. ; in absorbent power, from i to 8 or 9 Ib. of water per cubic foot ; and their resistance to pressure, from so low a figure as 500 Ib. to 8000 Ib. for the cubic inch. Indeed, many of the sandstones, from their softness and rapidity of disintegration when exposed to the weather, are altogether unfit for building, while others are so hard and silicious as to be better adapted for road-material than for the purposes of architecture. A great deal, however, depends upon the mode of tooling and bedding that is, upon the crushing and loosening of the surface particles in dressing, and upon the laying of the stone in its natural bedding or stratification. Much of the beauty of sandstone depends on its tooling notching, scabbling, pearl- ing, broaching, droving, or polishing, as the case may be ; and no laminated variety should be bedded otherwise than it was in the quarry, or the result will be flaking or peeling off in course of time, under the frosts of winter. Tooling or dressing is an important feature in the preparation of sandstones for ashlar fronts j for while polishing will bring out the beauty of one variety, vertical droving may be more suitable for a second, and parallel broaching or pearling may mask the grain or spot- tings of a third. For rustic work in basements and the like, nothing can excel a strong homogeneous sandstone. In selecting sandstones, the finer-grained, the more homoge- neous in texture, the least absorbent of water, and the freest from lime and iron, should be preferred. All blocks containing balls or nodules of sulphide of iron (iron-pyrites), should be carefully rejected, as in a few years such nodules oxidise, become blackish-brown, unsightly stains, and finally weather out into cavities.* The builder cannot have a better test of the durability of a sandstone than by observing it in the face of exposed cliffs and old quarries ; its absorbent nature he can test by experiment ; and in the case of a new variety, important information may be obtained by subjecting it to the process of M. Brard. This process consists in boiling small cubes of the stones to be tested in a saturated solution of sulphate of soda (Glauber's salt), and then suspending them for four or five days in the open air. As they dry they become covered with an efflorescence of crystals, which must be successively washed off till the efflorescence ceases. If the stone resists the decomposing action of damp and frost, the salt does not force out any portions of the stone with it ; on the other hand, if it * For want of selection, some of the finest frontages in Edinburgh exhibit such stains, and one church at the junction of Bristo Street and Forrest Road is absolutely pock-pitted with these unsightly blotches. 68 GEOLOGY AND ARCHITECTURE. yields to this action, small particles will be perceived to separate themselves, and the cube will gradually lose its angles and sharp edges. The amount of this disintegration affords, according to the author of the process, a criterion of what would be produced in course of time by the action of the weather. In the typical Siluria (Eastern Wales) of Sir Roderick Murchison, several tough-grained sandstones and grits are noted in the Geological Survey, but these, as far as we are aware, are not raised except for local and minor purposes. In other Silurian tracts, metamorphism generally prevails to such an extent as to convert the sandstones into jointed silicious grits and quartzites, unfitted for the requirements of the builder. The sandstones of the Old Red and Devonian Systems vary- very much in composition, colour, and durability, and usually present themselves in three available forms the compact liver- rock for building, the flagstones for paving, and the tilestones for roofing. The tilestones of Hereford, Forfar, and Caith- ness, are of reddish, rusty-grey, and bluish-grey tints, and when carefully selected stand the weather well, some of these used on ecclesiastical buildings of the fifteenth century being still fresh and serviceable. The flagstones of Caithness and Forfar are well and widely known, and though used in internal floorings, &c., are much more extensively employed for street purposes, under which head they are treated in the chapter on Geology and Civil Engineering. The sandstones proper vary very much in texture, and are of many colours brick-red, chocolate-red, rusty-grey, yellow, and creamy-white. Some of the Hereford and Monmouth beds are said not to be durable ; but many of the Perth and Forfar rocks tool well and stand well, and the same may be said of those of Cork and Kerry Carmylie, Leysmill, Turin, Glammis, Milnefield, Moncrieff, &c., furnishing good examples. The main objection to them is their dull rusty-grey tints, and the frequent embedding of pebbles or nodules of foreign matter. As they are tough and strong, however, and can be raised in blocks of any size, they are well fitted for harbours, sea-walls, and heavy structures, as may be seen in the docks of Dundee. Thebrick-red beds from the middle formation are generally less durable, though some of the Ross-shire (Munlochy) and Dumbarton beds stand fairly ; hut the creamy-white and yellow strata of the upper formation form most beautiful and durable building-blocks, as at Elgin, Kembach in Fife, and Denholm-Hill in Roxburgh- BUILDING-STONES. 69 shire. Like other sandstones, those of the Old Red stand the test of time very variously, as may be seen in the old ecclesi- astical structures of Elgin, Arbroath, Dunblane, Dryburgh, Melrose, Kelso, and Jedburgh, in Scotland ; in Tintern Abbey, the Castle of Chepstowe, in England ; and in the Round Tower of Ardmore, Ballymoney Castle, and other structures in Ireland. The sandstones of the Carboniferous System, from their ex- tensive development in Britain, are more largely employed than those of the Old Red, and are also much more varied in colour, texture, and durability. In colour they vary from white and whitish-grey to tints of greenish-grey, yellow, buff, brown, and red; in texture, from the finest and closest grain to coarse-grained quartzose and pebbly-quartzose grits ; and in durability, from rocks that will crumble down in a few years to others that will endure for ages. They occur chiefly as thick-bedded " liver " rocks; though many fields yield flag- stones of unequalled size and quality, as the millstone-grit and Gannister beds of Yorkshire, Derby, and Lancashire, the lower coal-measures of Edinburgh, and the lower coal-measures and millstone-grit of Carlow, Mayo, &c., in Ireland. These flag- stones, however, will be noticed as road-material under the head of Civil Engineering; and here we direct attention chiefly to -the thick-bedded sandstones used in building, and such as may be seen in Edinburgh, Glasgow, St Andrews, Newcastle, Leeds, Sheffield, Bradford, Manchester, and other towns situated on or near to the coal-formation. Many of the coal-measure sandstones may be raised in blocks of large size, are easily squared and tooled, and from their agreeable tints are employed not only in carboniferous areas, but in other and distant districts. We may notice in detail some of the better known and more esteemed varieties : The sandstones of Glasgow (Bishopbriggs, Gifthock, Dowan- hill, &c.) are of whitish tints, of medium texture, are easily squared and tooled, and of excellent quality, as may be seen in the structures of that city, from the old Cathedral down to the new University buildings, the modern warehouse, and sub- urban villa. Those of Stirlingshire (Polmaise, Dunmore, Plean, Bannock- burn, &c.) are of yellower and warmer tints, of fine texture, and stand well, as may be seen in Stirling Castle, Cambus- kenneth Abbey, and all the modern structures in the district. They are now largely carried to other localities, and even for frontages to London. 70 GEOLOGY AND ARCHITECTURE. Those of Edinburgh and Linlithgowshire (Craigleith, Ravel- ston, Redhall, Bellfield, Craigmillar, Joppa, Binney, Humbie, &c.) have all a high reputation, vary in shades from white to reddish-brown, are fine in texture, and of tried durability, as may be witnessed in the old baronial mansions of these counties, and in all the streets and public edifices, as well as elegant suburban villas, of the Scotch metropolis. The stones from Craigleith and Binney are carried to other districts of the country, and occasionally exported to the Continent. The sandstones of Fifeshire (Cullalo, Burntisland, St An- drews, &c.) appear in tints varying from the purest white to creamy yellow, are fine and rather soft in texture, but harden on exposure to the weather. The white rock of Cullalo (used in Fettes Hospital, Edinburgh) is an excellent stone, and has been exported to the Continent ; and that of St Andrews and neighbourhood, when carefully selected, produces a very satis- factory effect, and lasts well, as may be seen in the old cathe- dral and St Regulus' tower, erected in the ninth century. A variety of fine-grained black sandstone occurs at Carnock, near Dunfermline, which, when well designed and sculptured, has a very appropriate effect in tombstones and sepulchral monu- ments. Those of Newcastle (Elswick, Gosforth, Heddon, Kenton, &c.) are whitish-grey sandstones, rather rough and open in texture, and not especially durable, as may be seen in the old walls and churches of the town. Some, however, like those of Black Pasture on the North Tyne, and used in the pedestal of George Stephenson's monument, are of excellent quality the blocks in the Roman Wall from that quarry standing hard and fresh after an exposure of seventeen centuries. The beds quarried for millstones are of a finer and more equable texture. Some of the sandstones of Durham (Felling, Pensher, Leam- side, Stenton, &c.) are rather finer in the grain, tougher, and more argillaceous than those of Newcastle, but unless carefully chosen are also liable to weather and decay. Examples may be seen in Durham Cathedral, Barnard Castle, &c. ; and in several of the modern structures of Sunderland. The sandstones of Yorkshire differ much, according as they are raised from the millstone-grit or from the finer grained Gannister beds. The former yields coarse-grained, massive, greyish grits, which can be raised in large blocks (Leeds, Shef- field, &c.), fitted for heavy and durable structures. The Gannister beds, on the other hand (valley of the Aire, Brad- ford, Halifax, Huddersfield, &c.), are fine-grained, greenish- grey or yellowish-grey, flaggy beds, capable of being used either BUILDING-STONES. /I for building or for flagstones, as may be favourably seen in the recent public structures of Bradford. On the whole, Yorkshire is rich in carboniferous sandstones, which are em- ployed not only in its own populous towns, but carried to the towns of adjacent counties. Several of the grits and sandstones of Derbyshire make handsome building-stones, being of medium grain, of whitish or lightish-brown colours, and of tried durability. Bakewell Edge, used in Chatsworth Castle and Buxton Crescent, Duffield Bank and Morley Moor, in the public buildings of Derby, and Darley Dale in Darley Abbey and Stancliffe Hall may be taken as examples. The same remarks apply to the grits and sandstones of Lancashire, Gloucester, Staffordshire, and other adjacent carboniferous areas, all of which yield building-stones of varied texture, colour, and durability. The sandstones of the Permian or Longer New Red are usually of red and purplish tints, rather open and soft in tex- ture, and of no great durability. When carefully selected, however, both building-blocks and flagstones of fair quality can be obtained from the formation, as may be seen at Lochar Briggs and Corncockle, Dumfriesshire; along the Eden near Carlisle ; at Penrith and St Bees, in Cumberland ; and at Furness, in North Lancashire. The towns of Dumfries, Car- lisle, and Penrith, the Castle of Penrith, and the Abbeys of Lincluden, Furness, and Calder, may be taken as examples. The sandstones of the Trias or Upper New Red appear in various tints light-red, brownish-grey, white, and whitish- yellow are of varied texture and consistency, and, in conse- quence, of as varied durability. Many of the lower beds are soft, mottled, and worthless. The middle beds are of better quality, and occur largely in Lancashire, Cheshire, Stafford- shire, and Worcestershire. Some of the lower beds are quarried in the neighbourhood of Liverpool, and employed in the build- ings of that town ; but the upper and finer beds are (according to the Geological Survey) extensively raised and used in the construction of many of the churches and mansions of the midland counties. The quarries of Grinshill, near Shrewsbury ; of Hollington, near Uttoxeter ; Ombersley and Hadley, near Worcester; Park, near Tixall, in Staffordshire; Peckforton, in Cheshire ; and Manley, near Dunham, in Cheshire, are spoken of as yielding blocks of superior quality those of Hadley being employed in the restoration of Worcester Cathedral, and those of Manley, in that of Chester. These sandstones, how,- 72 GEOLOGY AND ARCHITECTURE. ever, are not comparable to those of the carboniferous system in point of texture and durability, and even the best of them require very careful selection. The sandstones of Lossiemouth and Cummingstone, in Morayshire (from their organic remains, regarded as of Triassic age) are of a superior quality the former whitish, fine-grained, thick-bedded, and capable of being raised in large blocks ; the latter brownish, fine-grained, thin-bedded, and affording very fair and flat-surfaced flagstones. The sandstones of the Oolitic and Cretaceous Systems are of rarer occurrence, and are only locally and partially employed for building purposes. The best known of these are, perhaps, those of Aislaby near Whitby, a light-brown, medium-grained, serviceable stone, from the Lias ; those of Calverly, near Tun- bridge Wells, and Horsham from the Wealden ; and the hard and fine-grained calciferous sandstone of Tisbury in Wiltshire. Those of Aislaby and Tisbury are superior freestones the former employed in Whitby Abbey, the latter in Salisbury and other places in the county. The Whitby sandstones have a high reputation, and are used not only in the locality, but carried to London, Cambridge, Exeter, and other towns. Limestones and Marbles. The limestones or calcareous rocks, employed in building, are not so extensively developed in Britain as the sandstones, nor are they generally made use of even in the districts where they occur. This arises partly from their unattractive tints, and partly from the difficulty of dressing and tooling them with effect ; the exception being some of the Oolitic and Mag- nesian varieties, which are both pleasing in colour and easily manipulated. Again, though standing well in the pure air of the country, many of them waste under the carbonated atmos- phere of towns ; and even the best of them, after a few years' exposure, have a bleached and cold appearance. They are found in all the geological systems, but in Britain most abund- antly in the Devonian, Carboniferous, Permian, and Oolitic. Those occurring among the Metamorphic rocks are generally marbles of crystalline texture, and some of the Devonian and Carboniferous limestones are also polished for decorative pur- poses ; but under the present head we refer only to those em- ployed by the builder. In structure the limestones are often jointed, and incapable of being raised in large blocks; in texture they vary from earthy to compact and subcrystalline, but, owing to their BUILDING-STONES. 73 organic origin, uniformity of texture is frequently interrupted by the remains of corals, shells, encrinites, and other exuviae. Many, however, of the Devonshire, Derbyshire, Yorkshire, and Westmoreland limestones are thick-bedded and homogeneous, and can be raised in blocks of great size and solidity. As ordinary limestones, they consist mainly of carbonate of lime, but dolomitic or Magnesian limestones consist of carbonate of magnesia and carbonate of lime, while throughout the whole family there may be argillaceous, silicious, ferruginous, and bituminous varieties. A family consisting of such members as chalk, oolite, dolomite, compact limestone, and crystalline marbles, must necessarily vary much in density, absorption, and resistance to pressure ; and hence such experiments as have been made must be received as applicable only to the rocks to which they relate. The limestones of the Metamorphic System are found chiefly in the Scottish Highlands, and are usually greyish crystalline varieties, or bluish and greenish veined varieties either raised for mortar and agricultural purposes, or occasionally as " mar- bles," to be noticed under another head. None of them are used as building-stones; and indeed, their paucity, the high angles at which they lie, and their distance from fuel, renders it often cheaper to bring lime from Carboniferous districts than to raise and calcine them in the counties (Banff, Aberdeen, Kincardine, Perth, and Forfar) where they occur. The limestones of the Silurian System are developed chiefly in Wales the Lake district and the southern uplands of Scot- land containing only a few sporadic and unimportant patches. Unless for country uses fences and farmsteads none of them are raised for better-class buildings, though the Wenlock beds are largely quarried for mortar, agricultural, and other purposes. The limestones of ti\z Devonian System are, as the name im- plies, mainly restricted to Devonshire. The calcareous beds of the Old Red Sandstone proper are limited and irregular, often silicious and concretionary, and seldom quarried unless on a very small scale for mortar and agriculture. The Devon- shire limestones, though perhaps better known as marbles, make also, when neatly squared and tooled, an excellent and durable building -stone. Plymouth, Torquay, Exeter, and many of the smaller towns in South Devon, contain structures of these limestones which are at once durable and of hand- 74 GEOLOGY AND ARCHITECTURE. some appearance. They are strictly marine limestones, often coralline, and frequently veined and mottled their prevailing tints being a light bluish-grey, with veins of white and creamy yellow. Reddish varieties are found in two or three localities, but these are chiefly raised for internal decoration shafts, slabs, and chimney-pieces. The limestones of the Carboniferotts System are largely de- veloped, both in thickness and extent, in England and Ireland ; but in Scotland the beds are thin and irregular, and scarcely suffice the local demands for mortar, the blast-furnace, and agriculture. In Derbyshire, Yorkshire, North Lancashire, and Westmoreland, there is a vast development of limestone, sev- eral hundred feet in thickness, and covering many square miles in extent. In North and South Wales there are similar though less extensive developments ; and in Ireland the greater portion of the central plain is occupied by limestones of the Carboniferous epoch. Several of these limestones are used as ornamental marbles (to be noticed under another section) ; the great bulk of them are quarried for the blast-furnace, for mor- tars, cements, agriculture, road-making, bleaching, tanning, gas purification, and other industrial purposes ; while only a small proportion is raised for building. They vary extremely in composition some containing upwards of 90 per cent of carbonate of lime, with minor proportions of silica, alumina, and oxide of iron; some containing from 10 to 15 per cent of carbonate of magnesia and passing into dolomites ; and others embodying such a large proportion of silica and alumina as to pass into cherts and hydraulic limestones. The following are analyses of a few varieties by the late Professor Johnston : Durham. Cumbld. Yorksh. Derbysh. Fifesh. Carb. lime, 95. 06 94.86 94.56 95-95 66.OO Sulph. do., . 0.23 0.32 0.24 Phosph. do., 0-33 Carb. magn., 2.46 1.26 2.32 0-54 9-45 Silica, . 1.32 2.92 1.29 2.O6 I 3- Alumina & ir n, i.oo 0-73 1.18 1. 21 8.71 Water, . 1.90 Bitumen, trace trace trace 0.94 As already stated, the unattractive colours of these moun- tain limestones, and the difficulty of tooling them, is against their wider adoption ; but many of them make strong, sub- stantial structures, and would be more generally employed, were it not for the abundance of available sandstones with which they are associated in> Carboniferous districts. As it is, many country mansions, public institutions, churches, and BUILDING-STONES. fo hotels in the counties above mentioned (Derbyshire, West Riding, N. Lancashire, Westmoreland, Glamorganshire, &c.), are constructed of them ; and in Ireland they have been simi- larly used from the time of the round towers downwards. Perhaps they appear to most advantage, whether in tooled courses or in rustic work, when accompanied by sandstone corners, rybats, and lintels. But even without these adjuncts, when their colour is light, and proper care bestowed on the size, arrangement, and tooling of the courses, they make hand- some structures in the pure air of the country, as may be seen in several of the old castles, churches, and public buildings in the districts above referred to. The limestones of the Permian System are mainly Magnesian that is, consist of carbonates of lime and magnesia, with vary- ing proportions of silica, alumina, and iron. If the silica is in ex- cess they become calcareous sandstones, generally of hard and close texture ; but when it constitutes only a small percentage, they are regarded as magnesian limestones. Many limestones in other formations contain small amounts of magnesia, but only those containing above 15 or 18 per cent are entitled to the name of " Magnesian." The more crystalline or dolomitic they are in texture, the more durable they become ; and those are most to be relied upon in which the lime and magnesia occur in nearly equivalent proportions. Generally, however, they exhibit great variety of texture and composition, even in the same quarry, and therefore require very careful and skilled selection. They derive their warm yellowish tints from the oxide of iron, assuming deeper tints as that ingredient prevails. In specific gravity they vary from 2 to 2.66 ; are much more absorbent of water than the sandstones; weigh from 128 Ib. to 152 Ib. a cubic foot ; and, in the more crystalline varieties, withstand a considerable crushing power. The following are analyses as given in the Commissioners' Report on Building- Stones, and by Richardson : Bolsover. Huddlestone. Roach Abbey. Park Nook. Fulwell. Carb. lime, . 51.1 54.19 57.5 55.7 62.80 Carb. magn., . 40.2 41.37 39.4 41.6 32.75 Silica, . j$ia 3.6 2.53 0.8 o.o trace Iron, Alumina, 1.8 0.30 0.4 0.4 2.30 Water and loss, 3.3 1.61 1.6 2.3 2.15 In England (for they do not occur either in Scotland or Ireland) these magnesian limestones occupy considerable areas in Durham, Yorkshire, Derby, and Notts, and appear in many varying beds (earthy, laminated, compact, concre- 76 GEOLOGY AND ARCHITECTURE. tionary, and crystalline), the whole series being from 200 to 300 feet in thickness. In Durham they are seldom used as building-stones, unless for rude walls and inferior structures. In Yorkshire they are, and have been, more largely raised at various places near Tadcaster, Sherborne, Doncaster, and Auston, and employed in various structures, but generally with varying results, as may be witnessed in the ecclesiastical buildings of York, Doncaster, Hull, Beverley, Selby, Ripon, and various parts of Lincolnshire. In Derbyshire the Bolsover Moor quarries, employed in the new Houses of Parliament, yield stones of varying quality some wasting and worthless, and others of fair durability. On the other hand, the cele- brated quarries of Mansfield, in Nottinghamshire, yield a silici- ous dolomite, of hard, close-grained, and enduring texture. Few rocks, indeed, vary so much in texture and durability as the magnesian limestones of England. In the same quarry, beds of tried excellence are frequently associated with others which look as well, but are worthless ; hence the skilled and watchful care that is requisite in selection. It is not only that they differ in composition the magnesia ranging from 45 down to 10 per cent and under but that they vary in textural aggregation from hard, compact, and crystalline beds to others that are so soft and earthy as to yield readily to the nail. The Oolitic limestones or calcareous freestones of the Jurassic System are largely employed for architectural purposes in the midland and southern counties x>f England, being pleasing in colour, easily raised and tooled, and of fair dura- bility when close-grained and homogeneous in texture. They are generally of whitish, cream-coloured, or light-brown tints ; vary in texture from compact small-grained roestones to pea- stones, and from peastones to coarse-grained, shelly, and coralline ragstones ; can be raised in blocks of any size ; and though soft when newly quarried, acquire hardness and toughness on exposure. Occurring in four zones of the system the Inferior Oolite, the Great or Bath Oolite, the Coralline Oolite, and the Portland stone they necessarily present great variety of colour and quality ; hence it is only the denser and finer-grained beds that are worked in their respective localities. The Inferior Oolite, which is largely developed in the Cotswold Hills, yields some fine-grained, compact, white or light-yellow beds, that are quarried at many places along the range Leckhampton near Cheltenham, Painswick, Breck- hampton, Ingleborough, &c. The Bath Oolite is still more BUILDING-STONES. 77 largely quarried, as well as raised from subterranean workings, along the Somerset and Wiltshire hills Stroud, Box, Chip- penham, Doulting, &c. and yields a fine, close-grained, whit- ish stone, which can be raised in blocks of any size, and though soft enough when first extracted to be cut with the saw, yet soon hardens on exposure. As this zone trends east- ward through Oxfordshire, Northamptonshire, and Lincoln- shire, it assumes browner and richer tints, and is quarried at several localities the quarries of Barnac and Casterton in Northamptonshire, of Ketton near Stamford, Haydor near Grantham, and Ancaster near Sleaford, being often referred to as yielding blocks of great size, pleasing tints, and tried durability. The Coralline Oolite, being inferior in texture and durability, is seldom used as a building-stone ; but the Port- land Beds have been long and largely quarried, and extensively employed in most of the public structures of London (St Paul's Cathedral and other churches), and in several of those of Dublin, as well as in many of the more important buildings in the south of England. When the Commissioners reported, in 1839, there were 56 quarries in the island, employing 240 quarrymen, and raising annually about 24,000 tons of stone ; and notwithstanding the greater competition with the Bath oolites, the demand, we believe, still continues. Throughout the whole zone of these Oolites, which stretches, in varying breadth, from Dorset to Scarborough, they have been, and are still, extensively employed in ecclesiastical structures, manor-houses, and public edifices in towns. When carefully selected, and not exposed to the carbonated atmos- phere of cities and manufacturing towns, many of them are of fair durability ; but even the best of them are not to be com- pared in this respect with the silicious grits and sandstones. For internal purposes, however, their pure colours, their light- ness, and the facility with which they can be carved, render them especially adapted ; hence the extensive use of such fine-grained varieties as those of Painswick, Box, and Caen in Normandy. In specific gravity the Oolites vary from 2 to 2.5; a cubic foot weighs, when dry, from 125 to 150 Ib. ; when dry they absorb from 8 to 10 per cent of their weight of water ; and in composition they are nearly pure carbonates of lime with minor proportions of carbonates of magnesia, silica, and iron. That of Bath, according to Daniell and Wheatstone,* consists of carb. lime 94.52, carb. mag. 2.50, iron and alumina 1.20, water and loss 1.78; and that of Portland, Report of Commissioners on Building-Stones. 78 GEOLOGY AND ARCHITECTURE. carb. lime 95.16, carb. mag. 1.20, silica 1.20, iron and alumina 0.50, water and loss 1.94. With the exception of the compact calcareous stone from Beer, in Devonshire, which has been employed in several local churches, and the Kentish Rag, which is quarried at several places along the outcrop of the Lower Greensand, there are no limestones worthy of notice employed in Britain for building purposes from the Cretaceous and Tertiary Systems, though they are largely employed in France and other foreign countries. Indeed, it is to tertiary limestones that Brussels and Paris owe much of their architectural beauty ; while the nummulitic beds have been used along their course as an available building-stone from the time of the Great Pyramid down to the present day. II. STONES FOR DECORATION AND SCULPTURE. Under this head we embrace such stones as are susceptible of a fine polish, and which are employed more for internal decoration and sculpture than for external buildings. It is true that many buildings are exteriorly ornamented with carvings and sculptures, but most of the stones used for interior decorations alabasters, marbles, serpentines, &c. would fare badly if exposed to the weather of a severe and variable climate. It is to those more exclusively devoted to ornamentation, therefore, that we devote the present section ; and first of the pyrogenous rocks. The Granites, Porphyries, Basalts, &c. Of recent years the Granites have come largely into use for external and internal pillars and pilasters, for mantelpieces, pedestals, vases, drinking fountains, graveyard monuments, and sarcophagi. This adoption has arisen partly from their sparkle and beauty, and the high polish of which they are susceptible, partly from their great durability, and partly also from the invention of mechanical appliances by which such hard sub- stances can be expeditiously and cheaply prepared. The granites of Aberdeen (Rubislaw, Stirling Hill, and Cairngall), of Mull, Dalbeattie, Shap, Dartmore, Wicklow, and Galway, are amongst the most esteemed varieties ; and there is scarcely a public building in any of our large towns, a first-class mansion-house, or fashionable cemetery, in which they may not be witnessed. It is needless to point to examples where the STONES FOR DECORATION AND SCULPTURE. 79 use is so frequent, and where year after year it is becoming more general as the wealth of the country increases, and as more effective machinery is invented for raising, cutting, and polish- ing the material. Having various shades of colour, various sizes of grain, and being capable of being raised in blocks of any dimensions (as already noticed under Building-Stones), the British Granites afford great variety of choice, from the warmer, tints suitable to a banqueting-hall, to the sombre and colder hues more appropriate to the monumental obelisk. The Porphyries, for the reasons stated in the preceding section, are very seldom employed in the United Kingdom for decorative purposes. This is not for want of beautiful tints or susceptibility to polish, but chiefly from their fissured and fractured structure, which renders them incapable of being raised in suitable blocks. Notwithstanding this drawback, they are occasionally used for smaller pedestals, vases, and the like, and several of them produce very fine effects. Indeed, were proper attention paid to the porphyries, some of the Cornish and Scotch varieties would, for internal decoration, compete successfully with the granites. In Scotland several of the porphyries, syenites, and syenitic greenstones are dressed and polished for curling-stones, on some varieties of which (Ailsa Craig and Blairgowrie, for example) connoisseurs set an especial value. The finer-grained Basalts, though successfully carved in ancient India and the East, are seldom, if ever, attempted in Britain ; and yet their dark colours, dull surface, and known durability, render them specially suitable for some kinds of ornamentation. Of the trap-rocks, few, indeed, are suitable for decorative or sculptural purposes ; and yet we have seen very handsome vases and minor ornaments fashioned of the variolitic amygdaloid of Glenfarg in Perthshire, and of the black-spotted olive-green variety of Hallyards in Fifeshire. Slates and Serpentines. The Slates, though they can be raised in slabs of any size, and cut into any form, are not susceptible of a high polish, and consequently are not used for decorative purposes, save when japanned or enamelled. In this state they are now extensively employed for chimney-pieces and table-slabs ; and very fair imitations of marbles (especially black), serpentines, and porphyries can be produced at a much smaller cost than the real materials. Being harder and tougher, the slates can 8O GEOLOGY AND ARCHITECTURE. withstand a much greater amount of tear and wear than either the serpentines or marbles. Abundant supplies of slab-slates, of great size and varying thickness, can be obtained from Valencia. Wales, and Windermere the Irish varieties being preferred by some for their toughness and greater regularity of grain, the Welsh for their smoother surface and easier manipulation. The Serpentines, so called from their mottled, serpent-skin- like appearance, are silicio-magnesian rocks of metamorphic origin arising apparently from the transmutation of mag- nesian limestones or other closely related strata. As the name implies, they are variegated in colour (green, grey, dark red, or brown), and often clouded, striped, or veined ; are rather soft and sectile ; have a dull, splintery fracture ; and like most magnesian minerals, feel greasy to the touch. Their average composition may be set down as 40 silica, 40 magnesia, and 13 water, with varying proportions of iron-peroxide, and traces of other colouring matter. Besides the common serpentine, known also as ophite or ophiolite, mineralogists distinguish noble serpentine, usually of some shade of green, translucent, and having a resinous lustre ; marmolite or foliated serpentine ; picrolite or fibrous serpentine ; and chrysolite or asbestiform serpentine, of a fine oil-green colour and silky lustre. " Of all the stones used for decorative purposes in architec- ture," says Mr Hull, in his work on building and decorative stones, "none surpasses in general estimation some of the varieties of serpentine. This is due both to the richness and variety of its colouring, and its capability of receiving a fine polish. It is not, however, adapted to outdoor use, especially in the smoky or gaseous atmosphere of cities ; for being acted on by hydrochloric and sulphuric acids, it is liable either to decay, or to become tarnished on the surface. But for indoor decorations, and the construction of slender shafts, pilasters, pedestals, vases, inlaid slabs for walls, and ornaments of various kinds, serpentine is often employed with successful results." Available serpentines occur in Cornwall and Anglesea in England ; in the counties of Banff, Aberdeen, Perth, and Forfar, in Scotland ; and in Galway and Donegal in Ireland. The most esteemed are the greenish-coloured of Galway, known to marble-cutters as " Connemara marble " or " Irish green : " the reddish, mottled, and clouded varieties of Lizard Point ; and the red and deep-green variety of Portsoy. At present the serpentines of Connemara and the Lizard are extensively in use; but that of Portsoy has been little employed, and only STONES FOR DECORATION AND SCULPTURE. 8 1 for minor ornaments, during the current century. At one time, however, it was exported to the Continent, and accord- ing to Mr Hay Cunningham e (* Geognosy of BanrTshire ') was used in decorating apartments in the palace of Louis the Fourteenth, under the title of Scottish marble Verde (FEcosse. The serpentines (verde antique of the ancients) occur abun- dantly among the metamorphic or crystalline rocks of most countries France, Germany, Italy, Greece, the Urals, Egypt, India, Canada, and N. America, yielding many varieties well fitted for architectural decoration, as well as for the production of articles of elegance and utility. Limestones, Marbles, Alabasters, &c. Under decorative limestones, we include such rocks as the Caen Oolite, which, being of fine texture and uniform colour, can be cut and carved into the most delicate and elaborate ornamentation. For internal carvings, and especially in eccle- siastical structures, few rocks can compete with this stone ; hence its extensive use in Britain, though very fair blocks for similar purposes can be obtained from the Box, Painswick, and Portland quarries. These limestones do not take a glossy polish like serpentines and marbles, but they are cheaply worked in comparison^ harden on exposure, and when broken or injured can be renewed with wonderful facility. Pillars, niches, statu- ettes, screens, altar-pieces, pedestals, pulpits, &c., in churches; and chimney-pieces, pedestals, pediments, and the like, in public halls, are abundantly chiselled from these limestones. Of all the ornamental and decorative stones, the marbles are the most abundant and varied, and at the same time the most extensively employed. Any rock susceptible of a fine polish is termed "marble" by the stone-cutter; hence we hear of " Connemara marble/' which is a true serpentine ; and of " Sicilian marble/' which is often a brecciated lava. The term, however, should be, and is, restricted by geologists to lime- stones capable of receiving a polish, and frequently exhibiting a variety of colours in veins and blotches. We have thus uni-coloured marbles, such as pure blacks and whites ; and party-coloured sorts, deriving their tints from accidental minerals, from metallic oxides, giving them a veined or clouded appear- ance, or from shells, encrinites, corals, and other organisms which impart a variety of "figure" as well as of hue. Every country has its own peculiar marbles, and almost every age has had its own whims and fancies for certain varieties. These varieties are almost endless Greece, Italy, Belgium, France, F 82 GEOLOGY AND ARCHITECTURE. Spain, Britain, the United States, and Canada, each yielding esteemed sorts, differing in colour, figure, lustre, and suscepti- bility of polish. The following are a few of the better known and more esteemed varieties, ancient and modern : Carrara, pure white, saccharoid, and semi-transparent ; highly esteemed for statuary purposes. Parian, of a waxy cream-colour, also crystalline, and employed in statuary. Giallo-antico, yellow, and mixed with a small proportion of hydrate of iron ; used for ornamental pur- poses. Sienna, a rich yellowish-brown, with lighter veins and cloudings. Rosso-antico, a deep blood-red, less or more veined. Mandelato, a light-red, veined and clouded. Verde antique, a cloudy green, mixed with serpentine, or serpentine itself. Cipolino, a mixture of talcose schist with white saccharoidal marble. Bardiglia, a bluish-grey variety, with bold black veins and cloudings. Lumachello or fire-marble, a dark-brown variety, having brilliant chatoyant reflections, which it owes to the nacreous matter of enclosed shells. Black marbles, like those of Derbyshire, Dent, and Kilkenny, deriving their dark colours from bitumen. Encrinal marbles, like those of Dent in Yorkshire and other carboniferous districts, deriving their " figure " from the stems and joints of encrinites. Shell marbles, like those of Purbeck and Petworth in Dorset and Sussex, and Kingsbarns in Fife, receiving their "figure" from the com- ponent shells of univalves and bivalves. The marbles are amongst the most varied and useful of rocks, whether for external structures or for internal decora- tion. They are sufficiently durable in dry and pure atmos- pheres ; can be raised, for the most part, in blocks of any size ; and are easily tooled and polished. As building-stones, they are unsuited for our climate; hence their use is principally confined to chimney-pieces, toilet and table slabs, inlaid works, mosaic pavements, portico and hall pillars, pedestals, busts, statues, and groups of statuary. Statuary marbles of the finest hue and texture are brought from Italy and Greece (Carrara and Paros), as are also many of the party- coloured varieties for internal decoration. Some beautiful marbles are also obtained from Belgium and France, but several useful sorts are derived from the formations of our own Islands Metamorphic, Devonian, Carboniferous, Oolitic, and Wealden and to these we shall briefly advert. The Metamorphic or Primary marbles of Britain are chiefly confined to the Scottish Highlands, and none of them have ever been worked to any extent for decorative purposes. They STONES FOR DECORATION AND SCULPTURE. 83 are found in beds of moderate thickness among the crystalline schists, which extend across the country from sea to sea, and are generally of grey or bluish-grey colours, with dove-coloured cloudings and occasional veins and blotches of green and yellow. They occur in lona, at Assynt, Glen Tilt, Ballachulish, Clunie, Kirkmichael, Banchory, and other places ; and though some, like Assynt and Glen Tilt, were at one time in use, they are now quarried solely for mortar and agricultural purposes. A pretty pinkish variety, with interspersed dark-green crystals of sahlite, is* found in the island of Tiree; but, so far as we are aware, it has never been worked to any extent for economic purposes, nor, indeed, is there any available amount of it. The Devonian or Devonshire marbles, on the other hand, are pretty extensively quarried, and consist of several varieties well adapted for chimney-pieces, pilasters, columns, inlaid slabs, mosaic-work, and other useful and ornamental purposes. The South Devon marbles, which are worked at Plymouth, St Mary's Church, Babbacombe, Totness, Newton Bushel, and other places, are of various shades of grey, with veins of white and yellow, occasionally reddish or flesh-coloured, with deeper veinings, and not unfrequently coralline or " madrepore." The marbles of St Mary's Church near Torquay, and Ipplepen near Totness, are much esteemed, and sent to all parts of the country. The North 'Devon marbles, though not so exten- sively quarried, present some useful varieties, having a black ground irregularly traversed with bold white veinings. Chud- ley, Staverton, and Berry Pomeroy, are mentioned by Mr Hunt, of the Museum of Practical Geology, as localities. The Carboniferous Limestones of the United Kingdom yield a great many marbles; but, with the exception of the pure black varieties, their colours are dull and uninviting, blues and greys being the prevailing tints. Their " figure," as the marble-worker terms it, is often their distinguishing peculiar- ity ; and this is imparted by imbedded fossils, such as corals, encrinites, and shells hence such technical designations as "encrinal" and "entrochal," "shelly" and "mussel," "bird's- eye " and " dog's-tooth," Though cheaply produced, the carboniferous marbles, with the exception of the black, are not in great request, their duller tints and want of lustre compared with the more crystalline limestones, their softness and doubt- ful durability, militating much against them. Notwithstanding these drawbacks, available marbles are procured in England from Ashford, Matlock, Bakewell, and other places in Derby- 84 GEOLOGY AND ARCHITECTURE. shire ; from Dent in Yorkshire ; from Kendal in Westmore- land ; from Anglesea, and from Poolwash, Port St Mary, and Scarlett, in the Isle of Man. Perhaps of these the best known and most esteemed are the black of Ashford, Matlock, and Dent; the brown or "rosewood" of Bakewell; the encrinal of Dent ; and the grey-shelly and encrinal of Poolwash. In Scotland, the mountain limestone, being thin and poorly de- veloped, affords no marbles ; but about the beginning of the century a shelly or " mussel marble " was worked at Kings- barns in Fife from the lower measures of the carboniferous system. In Ireland, on the other hand, where the mountain limestone is so extensively developed, there occur several excellent marbles black in Kilkenny and Galway ; grey, coralline, and encrinal in Cork, King's County, and Tipperary ; reddish and variegated in Armagh ; red and mottled in Lim- erick; and other veined and mottled sorts (reddish, cream- yellow, white, and brown) in several other counties. Indeed, according to Dr Kane's ' Industrial Resources of Ireland ' and the Reports of the Geological Survey, the country is rich in available marbles, presenting greater beauty and variety than those from the carboniferous limestone of England. From the Secondary Systems of England (for these are not developed to any appreciable extent in Ireland or Scotland) only one or two marbles are obtained, and those of very limited and local occurrence. The shelly laminated limestone of Whichwood Forest in Oxfordshire seems at one time to have been worked as a marble ; hence its designation in the oolitic system as the "forest marble." The thin fresh-water limestones of the Purbeck and Wealden formations were also at one time more extensively raised than now, as may be seen in the internal decorations and monuments of many of the old ecclesiastical buildings of the south of England. These marbles (known as Sussex, Petworth, Purbeck, and Paludina marble) are of a dull-grey colour, almost entirely composed of the shells of paludina, to the whorls of which they owe their figure rarely exceed a foot in thickness, and are now very seldom used, and only in the slender shaftings of pulpits and other church decorations. Of Alabaster which by some is said to derive its name from the Greek alabastron, an ink or perfume vase, and by others from Alabastron, a town in Egypt famous for the manufacture of such vases there are two well-known varieties, the gypseous and the calcareous. The former is a semi-trans- STONES FOR DECORATION AND SCULPTURE. 85 parent granular-crystalline variety of gypsum, or sulphate of lime, of various colours, but most esteemed when of a pure snow-white, and usually compact enough to stand the turning- lathe ; the latter is a carbonate of lime (oriental alabaster), usually white or yellowish-white, and found as a stalactite or stalagmite. The gypseous alabaster is a mineral of common oc- currence in secondary and tertiary formations (Cheshire, Wor- cester, Germany, Switzerland, the Tyrol, Montmartre near Paris, Volterra in Tuscany, &c.), and, being soft and readily turned by the lathe, is manufactured into vases, statuettes, cups, and other domestic ornaments. Very few of the British ala- basters are sufficiently pure and transparent for the finer orna- ments ; but masses of pale-pink and lighter shades are found as at Grantham, Newark-on-Trent, and other places which are used as adjuncts in pulpits, tombs, screens, and similar sculptured works. The headquarters of sculpturing in ala- baster are in Florence, Volterra, Pisa, and other towns of central Italy. This beautiful and semi-transparent variety of gypsum must not be confounded with the common massive sulphate of lirne (plaster of Paris or stucco-rock), which is not used with us as an ornamental stone, though in ancient times the purer and more compact sorts were employed in Nineveh, Egypt, Tuscany, &c., for sculptured wall-slabs, sarcophagi, cinereal urns, and other kindred purposes. The modern uses of common gypsum are noticed under the head of mortars and cements (Chap. VI.), and also under that of mineral manures (Chap. III.), to which, for further information, the reader is referred. Another beautiful variety of gypsum is the fibrous, known also as satin-spar, from its fine, glossy, and glistening lustre when cut and polished. It is found in thin veins and layers traversing beds of common gypsum, and is pretty largely manufactured into minor ornaments, such as cups, vases, neck- laces, bracelets, and the like. Some very pure bands occur in the gypsum of Chellaston Hill, near Derby, where, as well as at Bakewell, Matlock, and Buxton, it is fashioned into the above-named articles. Fluor-spar, which occurs in various colours blue, purple, green, and yellow is another calcareous mineral employed in the fabrication of minor ornaments. It is found both crystal- lised and crypto-crystalline in masses, not as an independent rock, but in veins and drusy cavities, in several formations, and in many countries. The variety most usually employed is "Blue John" or "Derbyshire spar;" and in several towns of 86 GEOLOGY AND ARCHITECTURE. that county it is fashioned, with rather pretty effect, into cups, vases, jars, obelisks, and various minor ornaments. Like alabaster, it is occasionally employed as an adjunct in sculptured work ; but, like alabaster and satin-spar, it is easily tarnished and far from durable. The gypsums rarely exceed 2 in the scale of hardness, and the fluors are about 5 ; and all, especially the pure white alabasters, require to be kept under glass shades to preserve their colour, lustre, and brilliancy. Rock-crystal, Agate, Jasper, &c. The rock-crystals, agates, jaspers, and other silicious stones, though frequently employed in inlaid work and fashioned into minor ornaments, come more appropriately under the head of Precious Stones (Chap. XVI.), where ample details will be found respecting their geological nature and occurrence. They seldom appear in masses of any magnitude, but are found in crystals, geodes, stalagmitic incrustations, and concretionary nodules. From this circumstance they are only fitted for smaller articles cups, boxes, vases, caskets, toilet-trays, knife- handles, and the like ; or, when sliced and polished, for several varieties of inlaid work, for which their hardness, variegated colours, and fine polish, render them extremely suitable. Though some beautiful specimens of cairngorm, agate, and jasper are found in Britain, Banffshire, Kincardineshire, For- farshire, and Ayrshire,* the finer and larger silicious stones are obtained from Brazil, Quito, Northern United States, Canada, Siberia, India and Ceylon, Egypt, Italy and Switzerland. Their hardness renders their preparation expensive; hence the comparative rarity and greater value of objects fashioned from rock-crystal, agate, carnelian, chalcedony, and jasper, compared with those from marble, alabaster, fluor, or other soft and less durable material. Under this head we might also notice jade, eclogite, garnet- rock, and other silicio-magnesian and silicic-aluminous rocks, which are frequently employed in ornamentation; but these, perhaps, will better be deferred till we come to treat of the precious stones in another chapter. Occasionally the septariti or bettle-stones (argillo-ferruginous nodules) of the coal and other formations, when of large size and sufficient solidity, are sliced for ornamental table-tops, and produce a fair effect. So also are the large silicio-calcareous fossil-trunks of Cold- * The yellow mottled jaspers of Ayrshire, and the red, banded, and mottled varieties found along the shores of Forfar, Kincardine, and Banff, make fair inlayings when well polished and assorted, though the nodules rarely exceed eight or ten inches in diameter. STONES FOR DECORATION AND SCULPTURE. 8/ stream, with their concentric rings, rays, and mottlings ; and the rolled flint conglomerate or puddingstone of Hereford- shire ; and not unfrequently blocks of cannel-coal, like that of Wigan and Wemyss, are cut, polished, and fashioned into tables, seats, vases, and other articles of fancy furniture. Such substances as these, however, have a local rather than a gene- ral interest. Here we may likewise advert to the Malachites or green carbonates of copper, which fall to be considered more fully as Precious Stones in a succeeding chapter (XVI.) When found in large and solid masses, as in the Urals, Northern States of America, and Burra Burra in Australia, they are successfully worked, by inlaying, into vases, tables, caskets, timepiece- stands, fireplaces, and other objects of internal decoration and ornament. The irregularly concentric layers of different shades of green occurring in the concretions produce, when skilfully sliced and united, a very rich effect, as was witnessed on a large scale in the Russian department of the Industrial Exhibi- tion of 1851. From her possession of the Urals, Russia is still the headquarters of malachite manufactures. Such is an outline and it is merely a sketch in outline of the stony substances employed in architecture and architec- tural ornaments. To have done justice to the subject from a builder's point of view would have required a volume ; but enough, perhaps, has been given to show how intimate and important are the relations which subsist between geology and the art of the architect. Though deficient in some of the ornamental stones, we possess within these islands abundance of building materials, at once beautiful and durable, and fitted for the requirements of every structure temple, tower, or palace ; suburban villa, rural cottage, or country mansion ; street-front, warehouse, or factory ; fortress, sea-pier, or dock- wall. And if it be that many of our public buildings are a reproach to us, and not to be compared, either in elegance, dimensions, or durability, with those of ancient Greece and Rome, it is not that we are wanting in materials or in skill to construct them, but because we live in an age of makeshifts, which seeks nothing beyond the necessities of present require- ments. Our granites, sandstones, limestones, and calcareous freestones give ample choice for every variety of structure, while our roofing-slates and flagstones furnish adjuncts unex- celled by those of any other country. It is true we are defi- cient in some of the finer stones for internal decoration; but even in this respect much more might be made of the granites, 88 GEOLOGY AND ARCHITECTURE. porphyries, serpentines, and marbles we possess, if sufficient time and labour or what is the same thing, sufficient outlay were spent on their preparation. So far as Geology is concerned, it has as yet but slenderly discharged its duty to the builder and architect. It has busied itself, and properly enough, with mapping out formations, making sections, and defining palaeontological zones; but it has done comparatively little in the way of pointing out the economic materials in these formations, or of indicating their relative values and appropriateness for special industrial pur- poses. It is one thing to determine the position, strike, dip, and thickness of a limestone, for example ; but it is another thing, and one of paramount importance, to indicate its special mineral character, so that some reliable inference can be drawn as to its fitness for building, for mortar, for flux, for hydraulic cement, or for other industrial applications. Until geological surveys supply this desideratum in a regular and systematic manner, they are only partially fulfilling their func- tion. It is surely as important to direct attention to rocks and minerals that may bear on the industrial purposes of civilised life, as it is to describe and dwell upon the remains of a life that has passed away. Both have their importance ; but the one need. not be exclusively studied to the detriment of the other. Above all, it is the duty of the economic geologist to note these things ever acting under the impression that much as may have been utilised, there are still many sub- stances in the earth's crust which can be turned to account in the increasing requirements of modern civilisation. Works which may be consulted. Hull's 'Treatise on the Building and Ornamental Stones of Great Britain and Foreign Countries ; ' Gwilt's ' Encyclopedia of Architecture, His- torical, Theoretical, and Practical ' Papworth's Edition ; Report of Commissioners on Building-Stones for the New Houses of Parlia- ment, 1839 and 1845. VI. GEOLOGY AND ARCHITECTURE. PART II. MORTARS, CONCRETES, AND CEMENTS. THE invention and preparation of mortars and cements form an essential department of architecture. It is not enough that we select stones of pleasing tints and durable texture; we must have some material capable of binding them together in one compact and substantial structure. Mere tooling and squar- ing may do for cyclopean walls ; well -worked clay may give a certain amount of solidity to lowly erections ; and bitumen, where obtainable, may give coherence to a pile : but what is specially needed is a substance easily applied, and which, in course of time, will undergo such a mineral change as to bind together with stony consistence. Such, in general, are the limes, mortars, and cements of the builder mineral pastes, if we may so speak which, when well prepared and tempered, become often tougher and harder than the blocks they are employed to cement. These preparations, though very numerous, and many of them patented, may be conveniently arranged for de- scription into Mortars, common and hydraulic; Cements, water and oil; and Concretes or Artificial Stones. Their in- gredients are all, of course, obtained from the mineral king- dom the great secret of their efficiency depending on the treatment of the raw materials, and the proportions of their admixture. I. LIMES AND MORTARS. The limestones which lie at the foundation of all these preparations are abundantly diffused through the stratified formations, there being scarcely a system which does not present one or more horizons of calcareous deposits. Indeed, every system from the oldest to the most recent has its lime- 90 GEOLOGY AND ARCHITECTURE. stones : the Metamorphic, its crystalline marbles ; the Silurian, its coralline and shelly beds ; the Old Red, its cornstones ; the Devonian, its coralline and shelly marbles ; the Carboniferous, its coralline, encrinal, shelly, and fresh-water beds; the Permian, its dolomites ; the Trias, its muschelkalks and gypsums ; the Jurassic, its oolites ; the Wealden, its shelly bands ; the Cre- taceous, its chalks ; the Tertiary, its gypseous and nummulitic strata; and the Post-Tertiary, its lacustrine marls. In Britain, the most of these are abundantly developed ; and for its area few countries can boast of such a varied and available supply. As mixed rocks they vary, of course, in composition, some being almost pure carbonates, some dolomitic or mag- nesian, and others sulphates or gypsums; while these varieties may again be less or more silicious, argillaceous, ferruginous, or bituminous. Whatever the varieties, or in whatever formations they may occur, the most of these limestones come to the surface in long stretches of outcrop, and are consequently quarried in open workings ; hence the numerous openings, great and small, on the chalks, oolites, magnesian limestones, and mountain limestones of England, and the mountain limestones of Ireland. England and Ireland are magnificently supplied with limestones ; Scotland but scantily so, and hence the more frequent recourse to mining of it in that country, as well as to its importation from the north of England and Antrim. In treating of these limestones in the present chapter, they may be conveniently considered under two main sections, ist, those suitable for ordinary building and plastering pur- poses ; and 2dly, those which are hydraulic, or harden and set under water. Mortar Limestones. The limestones best adapted for common or air-setting mortars, are the carbonates which are free from silica, alumina, and iron. These, as already stated, are very abundant ; and, after being quarried and broken into moderate-sized pieces, are calcined, either in temporary or in continual kilns, that is, in open kilns which are blown out till the calcined charge has been removed, or in draw-kilns, where the removal and charging proceed continuously. To avoid carnage, it is desir- able to have the kilns as central as possible to the face of the quarries ; and the longer the stone has been exposed to the air, the less fuel will it require to drive off the inherent moisture or quarry-water. The fuel employed in calcination is ordinary pit-coal ( i ton to 4 or 5 tons of limestone), and in remote LIMES AND MORTARS. 91 districts peat and brushwood ; but for some sorts of lime- stone, impure or shaly coals (while also much cheaper) are better adapted than the pure coals, as burning the stone more slowly and equally, as well as keeping it open and prevent- ing slagging and sintering. More kiln-dust may be produced by the use of these slaty coals, but fewer cores and slags will be found among the lime. When properly burnt that is, when not slagged or covered with a silicious glaze by too sudden ignition the limestone loses its carbonic acid, and is converted into caustic or quick lime (protoxide of calcium) 100 parts of the raw stone yielding 56 of burnt lime. This caustic lime is next slaked with water (i volume of water to 3 of lime), when it falls down, with violent evolution of heat, into a greyish, bluish, or brownish powder, according to the original colour of the limestone. By the application of more water it is converted into a pulp or paste ; and this pulp, thoroughly incorporated with three or four times its own volume of clean sharp sand, constitutes the common or air mortar of the builder. The proportion of sand should vary, of course, with the richness or " fatness " of the lime 2 or 2 Y? parts being sufficient for some poor limes, while some fat varieties will stand as much as 4 or 5 parts, and be improved by that proportion. The purer the carbonate the fatter the slaked lime. A great deal has been said and written by builders about the properties and admixtures of sand and lime,; which would be out of place to repeat in a work on Ecorfbmic "eology ; but this much may be observed as essential' to a^oodtAard-setting mortar : first, the more rapidly and corrfptetel).-. . ... 86.81 4.96 1.05 0.88 5.22 6.48 Wallsend, 1.28 83-47 6.68 1.42 0.06 8.17 0.20 Hedley's Hartley, I '3 I 80.26 5-28 1.16 1.78 2.40 9.12 Carr's Hartley, 1.25 79.83 5- 11 1.17 0.82 7.86 5.21 Brownhill, 1.25 80.03 5-o8 0.98 0.78 9.91 3.22 DERBYSHIRE : Elsecar, . > > H 1.29 81.93 4-85 1.27 10.91 8.58 2.46 Park Gate, .' .7.^ , i-S 1 80.07 4.92 2-15 i. ii 9-95 1. 80 Butterley, . . J \*$v 1.30 80.41 1-59 0.86 *y 11.26 1.23 Staveley, . . ; v?* 1.27 79.85 4-84 1.23 0.72 10.96 2.40 LANCASHIRE Inch Hall, .,.'.:./- 1.27 82.61 5-86 1.76 0.80 7-44 1-53 Pemberton, . ." 1,34 80.78 6.23 1.30 1.82 7. CO 2 34 Rushy Park, . ! i. * 1.28 77.76 1.32 I.OI / DO 8.99 O'T Wigan Cannel, ; j .* . 1.23 79-23 6.08 1.18 1-43 7.24 4.84 Balcarres, 5 feet, 1.26 74.21 5-03 0.77 2.09 8.69 9.21 Moss Hall, 1.27 77-50 5-84 0.98 1.36 12. l6 3-16 SCOTCH Dunfermline, W. 1.20 76.09 5-22 1.41 T 'S 1 5-05 10.70 Dalkeith, . I -3 I 76.94 5.20 trace 0.38 T 4-37 3-10 Eglinton, . Grangemouth, . 1.25 1.29 80.08 79.85 6.50 5-28 i-3S 1.38 1.42 8.05 8.58 2.44 3-52 1 FOSSIL FUELS. I6 5 Anthracite or Non-bituminous Coal. Anthracite may be defined as a species of coal wholly, or almost wholly, deprived of its bitumen or volatile ingredients. It may be regarded as a natural coke or charcoal, formed by subterranean or chemical heat. Ordinary bituminiferous coal is often found converted into a kind of coke by the contact of igneous rocks; and in this way some anthracites may have originated, though the majority seem to be the result of that slow change or metamorphism which all rock-masses undergo in the course of ages. As a mineral, anthracite occurs massive and amorphous, has a subconchoidal fracture, less or more of a metallic lustre, of a greyish-black or iron colour, streak un- altered, conducts electricity perfectly, and burns with a very weak or no flame. It varies greatly in composition, though good American sorts generally yield about 90 carbon, 3 hy- drogen, and 5 ashes, and the remainder oxygen and nitrogen. Submitted to the microscope, either in thin slices or in a state of ash, many varieties exhibit the vegetable structure, and leave no doubt as to the vegetable origin of all. Though not so generally convenient for fuel as ordinary coal requiring more care in kindling, and a strong draught when kindled it is rapidly rising in importance for the manufacture of the metals, for steam -raising, and even for household purposes, the United States consuming annually about 8 million tons. Anthracite, or at least anthracitic coals, are not uncommon in some of the Welsh and Scottish coal-fields. It occurs in Switzerland, France, and Germany ; and is especially abund- ant in the United States, as in Rhode Island, Massachusetts, and above all in Pennsylvania, where it seems to be an altered portion of the common bituminous coal of that region. The following analyses exhibit its ordinary composition : Sp. grav. I d 2 1 * Wg, 1-375 91.44 0.21 0.21 2.58 0.79 1-52 93 9.46 90.58 3-60 2.8 S 3 .8i ... 1.72 1.700 88.00 2.84 0.46 2.00 0.66 i. 80 90 8.50 1.810 83.00 3.00 0.50 1.88 2.00 79 Or, taking some of the more esteemed varieties found Wales, France, and the United States, we have : 1 66 HEAT AND LIGHT PRODUCING MATERIALS. WALES :- Neath Abbey, Swansea, Ystalyfera, . Cwm Neath, FRANCE: Cote d'Or, . Mais Saize, . PENNSYLVANIA : Beaver Meadow, . Shenoweth Vein, . Black-spring Gap, Nealey's, Tunnel, . MASSACHUSETTS : Mansfield Mine, . RHODE ISLAND : Portsmouth Mine, Carbon. 91,08 89.00 92.46 93.12 82.60 83-30 92.30 94.10 80.57 89.20 97.00 85-84 Volatile matter. Ashes. 5.01 7-50 6.04 5.22 8.60 7-50 6.42 1.40 7-lS 5-40 10.50 4.00 3-50 1.50 1.50 8.80 8.50 1.28 4-50 3-28 5-40 3-00 Besides the larger and purer sorts of anthracite employed in steam-raising and metallurgy, there are soft, earthy, and pul- verulent varieties known as culm, bastard stone-coal, lambskin, &c., which are used for lime-burning and other inferior pur- poses, or mixed with clay and formed into balls as a cheap household fuel. The preceding fossil fuels whether peat, lignite, bitumin- ous coal, or anthracite are all of vegetable origin, and only differ in the degree of mineralisation to which they have been respectively subjected. This is most convincingly seen from their chemical analyses, which exhibit the gradual loss of the gaseous elements, and the increase of fixed carbon in the pass- age of wood into peat, of peat into lignite, of lignite into coal, and of coal into anthracite and graphite. Thus : (At 212) Carbon. Hydrogen. Oxygen. Nitrogen. Inorganic Ash. Wood, . 48.94 6. 10 35-45 Peat, . - 56.66 5-9 18.33 2.4 1.6 Lignite, . * 56.70 3-7 13.27 I.O L^ Coal, . 70.92 2.6 1.8 0.2 3- J 5 Anthracite, 74-94 1.4 o-3 trace I -7 Graphite, 90.98 ... 1-7 According to M. Fremy the following are the degrees of alteration of woody tissue : i. Turf and Peat. Characterised by the presence of ulmic acid, and also by the woody fibres or the cellules of the medullary rays, which may be purified or FOSSIL FUELS. 167 extracted in notable quantities by means of nitric acid or hy- pochlorites, in which they are insoluble. 2. Fossil Wood or Woody Lignite. This, like the preceding, is partially soluble in alkalies, but its alteration is more advanced, for it is nearly wholly dissolved by nitric acid and hypochlorites. 3. Com- pact or Perfect Lignite. This substance is characterised by its complete solubility in hypochlorites and in nitric acid. Alka- line solutions do not in general act on perfect lignites. Re- agents in this variety show a passage of the organic matter into coal. 4. Coal. Insoluble in alkaline solutions and hy- pochlorites. 5. Anthracite. An approximation to graphite ; resists the reagents which act on the above-mentioned com- bustibles, and is only acted on by nitric acid with extreme slowness. Coke. Coke, or carbonised coal, which is now largely used as a fuel for metallurgical purposes, may be regarded as an artificial an- thracite. It is extensively prepared in the north of England from the smaller dross of the coking-coal of that district, and when well burnt from carefully cleaned material, consists of from 85 to 92 carbon, 3 to 5 ash, and 5 to 10 hydroscopic moisture. The amount of coke obtained from different coals varies very widely, some yielding upwards of 80 per cent, and others less than 50 ; but both amount and quality depend greatly upon the mode of treatment. The main purposes to be subserved by the manufacture of coke are the concentration of the carbon so as to yield a more intense heat than coal ; to get rid of unpleasant vapours and odours ; to prevent caking and produce free burning in the furnace ; and to get quit of as much as possible of the sulphur which may be contained in the pyrites of the coal. It is prepared in ovens, kilns, and retorts, but almost exclusively in ovens, hundreds of which are now utilising thousands of tons of dross and culm, which thirty years ago were consumed at the pithead as worthless, or never brought to bank. There are various constructions of oven (French, German, and English), and various methods of cleaning and washing the raw material, the main object being to produce a hard, uniform, and compact coke, as free from sulphur and earthy impurities as possible. In some ovens the gases and vapours evolved during the combustion of the coal escape unused ; in some they are collected and used as fuel for coking the coal, &c. ; and in others they are condensed, collected, and utilised for the preparation of ammoniacal salts. Like anthracite, coke 168 HEAT AND LIGHT PRODUCING MATERIALS. is ignited with difficulty, requires for kindling a strong red heat, and a steady blast or draught to insure continuous burning. The preparation of coke is annually on the increase, especi- ally for iron and steel manufacture ; and one has only to ob- serve the thousands of truck-loads which daily pass along the Durham railways to be convinced that it has now become one of the staple industries of the country. The amount carried from Durham to Cleveland and Barrow -in -Furness is of it- self sufficient to prove the magnitude and importance of this variety of fuel. Petroleum Crude Oil Coal-Gas, &c. Native petroleum, the crude oil obtained from the distillation of bituminous shales, and coal-gas, have recently been the sub- jects of experiment to see how far they could be regulated and rendered available as heating materials. The experiments have hitherto been somewhat unsatisfactory when conducted on the large scale ; but this has arisen more from the nature of the ap- pliances than from the character of the materials employed. The theoretical evaporative power of petroleum, paraffin -oil, and coal-gas, far exceeds that of coal or anthracite; and if proper appliances could be invented and the materials produced at available prices, there seems no reason why substances so con- centrated and unattended by refuse should not be employed, even on the largest scale. In the mean time, for small steam- boilers, for lamps, grates, stoves, and similar domestic purposes, oils and gases are coming more and more into use as cheap and effective fuels. Patent, or Artificial Fuels. Under this name a great many compounds (most of them patented) have recently been brought before the public, and especially since the increased price of ordinary pit-coal. The bases of most of these fuels are coal-screenings, dust or dross, with various admixtures of coal-tar, clay-liquor, or pulped peat, to give them coherence and consistence. During the last and early in the current century, similar attempts were made to uti- lise coal-screenings, slack, and dust, by semi-fusing or caking the material and pressing it into moulds ; but these attempts failed, partly from the expensive nature of the processes, and partly from the difficulty of igniting the blocks which had been largely deprived of their bitumen. Now, the raw material is simply mixed with some pulpy or tenacious substance to give it coherence, and compressed into blocks of convenient dimen- sions. In some instances the coal or coke waste is washed LIGHT-PRODUCERS. 169 before being used ; but in all, the material is granulated or re- duced to fragments, incorporated with the liquor or pulp, and then pressed into blocks or briquettes of greater consistency than either coke or coal. From their shape these briquettes can be stored away in small space on board ship; and for domestic use afford a cleanly and cheerful fuel. As yet the consumption of these artificial fuels has not been on a large scale in Britain, but on the Continent several of them (Peras, Parisian Coal, Charbon Briquettes, &c.) are in consider- able demand at about two-thirds the price of ordinary house- hold coal. The amount of patent fuel prepared in Britain dur- ing the year 1872 was about 230,000 tons, of which not fewer than 207,241 were exported to foreign countries. Of these fuels, Wylam's, Barker's, Bell's, &c., are well spoken of, and may, under the continued high price of coals, come more largely into use. In America, the artificial fuel of Capt. Hays (an ad- mixture of anthracite dust, clay-pulp, and coal-tar) is highly commended, and can be produced at little more than half the price of the anthracite itself. The following are analyses of some of these artificial fuels : - 1 Carbon. Hydrogen. Nitrogen. 1 in I < 1 Wylam's, . .10 79.91 S-69 1.68 1.25 6.69 4.94 65.8 Bell's, Warlich's . , .. .- .14 87.88 90.02 5.22 0.81 trace 0.71 1.62 0.42 in ash 4.96 2.91 71.7 85-1 Barker's, . .28 92.00 ... 1.05 ... 4.00 87,S Livingstone's, Lyon's, .18 13 85.07 86.36 4-13 4.56 ... 1.29 2.03 2.07 4-52 4.66 * Volatile matters, 6.70. II. LIGHT-PRODUCERS. The conversion of wood, vegetable and animal oils, fats, wax, gums, and resins into inflammable gases, is the usual and primi- tive mode of supplying artificial light ; but as man gathers in large communities and requires more brilliant and abundant illumination for his cities, workshops, and public buildings, the primitive sources become insufficient, and, as in the case of fuels, he has to have recourse to the mineral kingdom. From this he derives certain hydrocarbons jjaphtha, petroleum, I/O HEAT AND LIGHT PRODUCING MATERIALS. asphalt, bituminous shales, and coals ; and from these, by chemical and mechanical appliances, he obtains the most copi- ous and brilliant illuminating materials. Naturally the hydro- carbons are very volatile and unstable, and thus, on exposure to the air, pass into each other limpid naphtha into petroleum, petroleum into mineral pitch or bitumen, and bitumen on further exposure into asphalt. Without much scientific error they may be described under the following heads : Gas and Naphtha Springs. In the working of coals and lignites, and occasionally in bor- ing in carboniferous, lignitiferous, and saliferous districts, dis- charges of carburetted hydrogen are met with, and those in some instances have been collected and lighted. In the neigh- bourhood of Fredonia, State of New York, a gas-spring from bituminous limestone is said to yield about 800 cubic feet in twelve hours, and this is collected and used for lighting the locality. According to Fouque, it is an admixture of marsh gas (CH 4 ) and hydride of ethyl (C 2 H 6 ). The salt-mine of Szlatina, in Hungary, is also said to be lighted by gas exuded from its beds of bituminous marl-clay ; and in China, accord- ing to the Rev. Mr Imbert, gas springs from the salt-bearing beds of Szu Tchouan are collected and carried in bamboo tubes both for the purposes of lighting and heating. In our own coal-fields (as at Killingworth, Jarrow, and Usworth, near New- castle) blowers of gas are sometimes persistent for years, though not, so far as we are aware, turned to any useful account. Gen- erally speaking, however, such issues are uncertain, and after a few months' or years' escape, get exhausted, and disappear. Gas-springs occur also in volcanic and convulsed tracts, but are usually too varied in their composition and too uncertain in their discharge to be used economically. Naphtha, which is a limpid, volatile, and highly inflammable variety of bitumen, is found exuding from rocks and soils in volcanic countries, and also in tracts where coals and lignites seem to be undergoing a slow natural process of distillation. One of the finest and purest varieties is that obtained from Baku and Scamachia on the western shores of the Caspian, where it rises from calcareous rocks in the state of an odorous inflammable vapour, or is collected in the liquid state by sink- ing shallow wells. Naturally it is of a yellowish colour, but may be rendered colourless by distillation. Its specific grav- ity is about .75; it boils at 160, and appears to be a pure hydrocarbon, consisting of 86 carbon and 14 hydrogen. Most of the naphtha of commerce is obtained from the distillation of LIGHT-PRODUCERS. I J I coal-tar, or directly from coals and bituminous shales. Owing to its volatile nature, it is somewhat dangerous as a lighting oil, and requires great care in its manipulation. Petroleum and Oil- Wells. Petroleum, or rock-oil, so called from its oozing out from certain strata like oil, is usually of a dark yellowish-brown colour, more or less limpid, according to external tempera- ture, and consists of 88 carbon and 12 hydrogen. It occurs in various formations, chiefly in connection with fields of coal and lignite, and appears to arise from the decomposition or distillation of the strata by slow subterranean heat. In general, it comes to the surface associated with water ; hence the " oil-wells " of America, Canada, Trinidad, Persia, Burmah, and other countries, which are now largely worked for distil- lation and rectification into illuminating oils, naphtha, and other similar products. Many millions of gallons are annually procured from the preceding districts ; and when properly rectified, and burned in suitably constructed lamps, the par- affin-oils afford at once a safe, brilliant, and economical light. " A good petroleum oil (Dingl. polyt. J., ccxi. 76) should be colourless or light yellow ; its smell should not be unpleasant ; its specific gravity at 15 should not exceed 0.804, an d should not be under 0.795. When shaken with a mixture of equal volumes of sulphuric acid and water, it should impart a pale yellow colour to the acid, and itself become less coloured ; and finally, heated to 34, it should not burn when a light is applied." While petroleum occurs most abundantly in carboniferous and lignitiferous formations, it is found also in strata of all ages, from the Silurian upwards. The oil-wells of Canada flow from Silurian and Devonian rocks ; those of the United States from Devonian and carboniferous; those of Trinidad from tertiary lignites ; those of the Caspian and Persia from tertiary shales and limestones ; and those of Rangoon from tertiary and post-tertiary clays and lignites. Indeed, mineral oil seems to be a product of all ages ; and while the greater portion undoubtedly arises from the slow decomposition of vegetable matter, some of it may also be due to the decomposition of animal remains fishes, shell-fish, Crustacea (the trilobitic shales of Canada), and the minuter forms of life which enter largely into the composition of many shales, limestones, and other strata. Abich has sug- gested that bitumen may be a primitive compound, engendered in the interior of the earth, like carbonic acid and nitrogen, the 1/2 HEAT AND LIGHT PRODUCING MATERIALS. real origin of which is also unknown ; but in the present state of our knowledge, the decomposition of organic (vegetable and animal) substances offers the most satisfactory solution. In many instances the petroleum merely oozes or trickles out from the crevices of rocks ; in others it oozes through clays and sands, and can be collected in shallow wells : in some cases, it comes up with springs of water, and floats on their surface ; in others, as in North America, when the oil is " struck," it bursts forth from the bore-hole in conjunction with water with great force, as if it had been pent up in subterranean reservoirs; and not unfrequentlyin such wells its flow is intermit- tent and irregular. " The average depth " (says Dr Gesner, writing in 1861) " at which oil is obtained, has not yet far ex- ceeded 250 feet.* Deeper sinkings may hereafter be found profitable. Carburetted hydrogen gas frequently escapes from the pipe, when it is first let down into the earth, and sometimes salt water rises with the oil. So great is the discharge of the petroleum in some instances, that sufficient vessels cannot be obtained for its reception, and it runs in oily streams over the surface. Some springs yield 200 barrels a-day; and a reservoir near Tideout, Erie county, Pennsylvania, when first struck, discharged 300 barrels. Accurate records have not been kept of all the strata penetrated ; but they appear to consist chiefly of limestone, sandstone, and shale.' ; We may add that at the present moment (1874) several springs are said to be running 500 barrels a-day ; hence the unequal and unprofitable com- petition between the British shale-oil manufacturer and the American importer. In whichever way the supply may be obtained, the trade in mineral oil has, during the last fourteen years (since 1859), assumed most gigantic proportions, and has become a new source of industry and wealth, not only in America and Canada, but in Trinidad, Italy, Spain, Switzerland, Germany, Turkey, Russia, Persia, and Burmah. Indeed, the occurrence of petro- leum may be said to be world-wide, though few regions can vie with those of the Caspian, Rangoon, California, Canada, and the United States', where the oil-region includes a vast tract of country (computed at 63,000 square miles) running parallel with the Alleghany Mountains, and extending from Lake On- tario on the north, to the valley of the Kanawha, in Virginia. * In Canada, many borings have been carried down to 500 feet, and occa- sionally without striking oil. When this happens, the bore is said to be a "dry hole;" and it is not unusual to send down an "earthquake shell," which, on explosion, so shatters the surrounding rock as to let in the oil from any veins or fissures that may lie within the sphere of its action. LIGHT-PRODUCERS. 173 The natural distillation of bitumen is a slow and gradual process, and may go on for ages, or in other words, till the American Oil-Weil (after Gesner). vegetable masses producing it be thoroughly debituminised. The petroleum well of St Catherine's, near Edinburgh, arising from lower carboniferous shales, is mentioned early in the fifteenth century, and it still yields a small but regular amount of dark- brown bitumen, which floats as a scum on the slowly issuing water. Oil-wells,' like many of the North American, which gush forth with great violence at first tapping, gradually become weaker, and often cease altogether. In such cases, what nature has been distilling and accumulating under pressure for ages, is rapidly discharged from the bore-holes, and the future supply is thus limited to the amount which nature annually distils. If the bituminiferous rocks be still undergoing metamorphism, a cer- tain amount of petroleum may be looked for ; but if the metamorphism has become complete, no further supply can be ob- tained. In either case the oil-supply of America, gigantic as it is, must by-and-by diminish, and all 1/4 HEAT AND LIGHT PRODUCING MATERIALS. the more rapidly, the more extensively and energetically the area is tapped and drawn from. On an average, one hundred barrels of crude or natural petroleum yield about seventy-five of refined oil. Solid Bitumens Pitch, Asphalt, &c. Bitumen, in its purest and most fluid state constitutes naphtha (86 carbon, 14 hydrogen) ; when of the consistence of oil, it is known as petroleum (i to 8 per cent of nitrogen, oxygen, and ashes) ; in its next state of inspissation it is called maltha, or slaggy mineral pitch ; then elaterite, or elastic bitumen ; and ultimately, on further exposure to the air, it becomes indurated into asphalt, which varies considerably in purity some speci- mens yielding from 8 to 14 per cent of oxygen and nitrogen, and from 4 to 6 of inorganic ashes. Besides mineral pitch and asphalt, there are other viscid and solid hydrocarbons, as elaterite, hatchetine, ozokerite, &c. ; but with the exception of maltha, asphalt, and ozokerite, none of them appear in such quantities as to be of commercial importance. Available ac- cumulations of pitch and asphalt are found in Trinidad, Bar- badoes, Cuba, Canada, Virginia, Texas, France, Switzerland, Turkey, Persia, and India sometimes in solid exudations, as in Trinidad, Texas, and Virginia, and in other cases in com- bination with gravels, sandstones, and limestones. " The cele- brated pitch-lake of Trinidad, says Dr Gesner, is upwards of three miles in circumference, and forms the head of La Brae harbour. At the time of my visit, the bitumen, of the con- sistence of thin mortar, was flowing out from the side of a hill, and making its way outwards over more compact layers to- wards the sea. As the semi-solid and sulphureous mineral ad- vances and is exposed to the atmosphere, it becomes more solid ; but ever continues to advance and encroach upon the water of the harbour. The surface of the bitumen is occupied by small ponds of water, clear and transparent, in which there are several kinds of fishes. The sea, near the shore, sends up considerable quantities of naphtha from submarine springs, and the water is covered by an iridescent film of oil. In the cliffs along the shores there are strata of lignite, in which it has been supposed by some the bitumen and naphtha have their origin." Whatever their origin and mode of occurrence, these bitu- mens require conversion either into oils or gases before being available for lighting purposes, and several ingenious processes are in use for such conversion. The mineral fats and tallows are rarely in abundance sufficient for economic uses; but LIGHT-PRODUCERS. 1/5 where, like the ozokerites of Galicia and Bohemia, they occur in considerable quantities, they are usually distilled, and con- verted into paraffin-oil for lamps, and into solid paraffin for the manufacture of candles. The Galician ozokerite is said to contain about 25 per cent of solid paraffin, while the Scottish oil-shales ordinarily yield not more than 2 per cent. Other substances fitted for the production of oils have more recently come into notice, such as the " turbite" of Brazil, the " white coal" of Australia, and the " Waitata shale" of New Zealand, all of which seem to be recent clayey deposits largely impregnated with bitumen. Albertite or Albert-Coal. Another bituminous mineral, known as Albertite or Albert- Coal, from its occurrence at Hillsboro', Albert County, New Brunswick, is also of importance as an abundant light-producer. At Hillsboro' it appears as an injected vein, situated almost vertically in the earth, and from one to sixteen feet in thick- ness. It is associated with rocks highly charged with bitu- men, and has neither roof, floor, nor other accompaniments which distinguish seams or beds of true coal. Asa mineral, it is black and brilliant as jet, breaks with a fine conchoidal fracture, and does not soil the fingers. It melts and drops in the flame of a candle, and dissolves in naphtha and other solvents, forming a varnish. It has all the essentials of an asphalt, and according to Gesner consists of carbon, 85.40 ; hydrogen, 9.200; nitrogen, 3.06; sulphur, a trace; oxygen, 2.22 ; and ash, 0.12. On an average it yields no gallons of crude oil per ton, of which 70 per cent may be made into a brilliant lamp-oil. This mineral has also been discovered in veins near the junction of the Old Red Sandstone and Metamorphic Schists of Sutherlandshire, in Scotland ; but the veins rarely exceeding one or two inches in thickness, render it commercially unavail- able. It is of very fine quality, however, being even more compact and lustrous than the Hillsboro' variety. Peat. It has also been attempted to employ peat, which occurs in inexhaustible supplies, as a light-producer. Good varieties of Irish peat are said to have yielded to the Irish Peat Company 3 Ib. of paraffin, i gallon of lamp-oil, and 2 gallons of lubri- cating oil per ton. In Sir James Matheson's work at the Lews, 100 tons of peat give, it is said, about 7 per cent of tar, which yielded, on an average, a weekly produce of 749 gallons i;6 HEAT AND LIGHT PRODUCING MATERIALS. of illuminating oil. When prices were at 2s. a gallon, this gave a handsome profit ; but petroleum has not for years brought half the sum, hence the discontinuance of the oil-manufacture, and the application of the tar to ship-yard purposes. So long, indeed, as the richer petroleums, bituminous shales, and oil- coals, can be had in abundance, it seems impossible to utilise peat in this direction. Bituminous Shales. In many geological formations tertiary, cretaceous, oolitic, triassic, and carboniferous there occur dark coaly-looking beds, generally known as bituminous or bituminiferous shales. Some of these approach almost to the character of coals, while others are merely dark-coloured argillaceous strata. They are all evidently old estuarine and marine muds, and differ in aspect and quality according to the amount of vegetable matter that enters into their composition. Geologically, they occur interstratified with the sandstones, limestones, fire-clays, coals, and ironstones of their respective formations, and vary in thickness and quality like the other strata, some beds being wholly available for the retort, others only partially so, and some very thick beds having one or more layers of superior richness. They are mined like ordinary coals, but, from their tough flaggy character and unequal thickness, require a some- what special manipulation. Some of the wealden and oolitic shales are of fair quality, and might be distilled for certain purposes fuel and gas- making but not, according to past manufacturing experiences, for illuminating oils.* It is chiefly those of the carboni- ferous system that since 1858 have been brought into use for the distillation of paraffin and paraffin-oils crude or lubri- cating oil, rectified or light oil, solid paraffin, mineral spirits, and ammonia, being among the products obtained during their distillation and rectification. Bituminous shales occur in most of our British coal-fields ; but hitherto it has been mainly those in the lower coal-measures of Linlithgow, Lanark, Ayrshire, Fife, and Mid-Lothian, that have been largely raised for this species of manufacture. Indeed, the mining and distillation of * According to Dr Hoffman, the Kimmeridge shale yields to analysis : Mineral matter, . . . . . ..... 23.5 Carbon, ....... 19.5 Light oil, .... L '<-; . 2.3 Heavy oil, containing 1.9 per cent paraffin, . . 36.7 Gas, water, ammonia, &c., . . " ,. ' 18.0 LIGHT-PRODUCERS. 1 77 shales have created quite a revolution in the industry and as- pect of some districts like Linlithgowshire ; and estates which sixteen years ago brought only a few hundreds per annum to their proprietors now bring as many thousands, and hamlets of a few houses are now large and busy towns. All this has arisen since the introduction of Young's process for the distilla- tion of coals and shales at a low red heat, whereby condensable gases are given off, and these subsequently reduced to crude oil, and the crude oils rectified into light paraffin-oil solid paraffin, ammonia, mineral spirits, &c., being among the usual products of rectification and treatment. Few branches of in- dustry have had such a marvellous and rapid rise as that of the production of shale-oils; and as the supply of the raw material is practically unlimited, and the pressure on gas- coal becomes more and more severe, we may still look forward to its further extension and improvement not only for the manufacture of paraffin-oil and paraffin-candles, but for the production of crude oils for conversion into dry gas for the lighting of workshops, factories, and country mansions. Many of the shales now used yield from 1 8 to 80 gallons of crude oil per ton, a superior shale being characterised by its lightness, toughness, or " boardiness " as the miners term it, and by its brown streak. The following are analyses of some of the better known oil-yielding substances, as given by Dr Gesner in his ' Treatise on Coal, Petroleum, and other Dis- tilled Oils,' and by other authorities : Volatile Gallons of crude Locality. matters. Coke. oil per ton. Torbane Mineral, . 70.10 29.90 120 51. 49. 96 12. 00 Lesmahago Cannel, . Leeswood Green Cannel, Kimmeridge Shale, Wigan Cannel, Derbyshire Cannel, . Poole Shale, Newcastle Coal, Albertite, N. Bk., . Stellarite, Nova Scotia, Hartley Cannel, N.S.W., Asphalt Rock, . Pictou Shale, N.S. . Breckenridge Coal, U.S., Arkansas Bitumen, . Canada Petroleum, . Virginian n West Lothian Shales, 44. 56. 74 48-36 53. 82 42. 58. 50 35- 65. 48 61.30 30.65 no 65.56 25.23 zoo 140 43- 57- 64 27- 73- 47 61.30 3 -65 130 60. 60. 64 70. 30. 118 60. 40. 170 25-45 Cannel Coals Gas-Coals. However useful and well adapted for many purposes the naph- thas, petroleums, paraffins, and paraffin-oils may be, there is no M 1 78 HEAT AND LIGHT PRODUCING MATERIALS. lighting substance as yet known so convenient, so easily dis- tributed, so eminently under control, and withal so brilliant, as common illuminating coal-gas. Compare the gas-jets of our streets, shops, and factories with the whale-oil lamps of fifty years ago, and it will at once be admitted that few inventions have been so useful and successful as the manufacture and distribu- tion of this familiar illuminator. Under proper treatment any variety of bituminous coal will yield an illuminating gas, and a great proportion of our towns derive their supplies from this source. Of course, bituminous coals vary much in their quality; and while some, like the best Newcastle, will yield from 9000 to 9500 cubic feet per ton, others of a harder and drier nature will yield little more than half that amount. Again, some are freer from sulphide of iron and other impurities, and require less purification ; others, after distillation, leave a firm and avail- able coke ; while many that yield a fair percentage of gas leave but a soft and worthless residue.* In the choice of a coal the gas-manufacturer has to take these and other circumstances into consideration, and it is greatly owing to his skill in selection and treatment whether a gas-work will yield a satisfactory or unsatisfactory return to its shareholders. Indeed, eminent as many of our gas-engineers undoubtedly are, there is still much to be learned in the matter of retorts, the nature of coals, the temperature of distillation, the subsequent processes of purification, and the utilisation of by-products. But while ordinary bituminous coals are used in many, per- haps in the majority of gas-works, the " cannels," " parrots," or, as they are often termed, "gas-coals," produce, on the whole, not only a larger amount, but a superior quality of illuminating material. These cannels, like other coals, vary in appearance and quality ; but, generally speaking, they are compact and jet-like in texture, brittle, break with a conchoidal fracture, are more or less lustrous, and do not soil the fingers when handled. They occur most abundantly in the Lanca- shire, Yorkshire, North Wales, and Scotch coal-fields ; and are said to be called "cannels" from the candle-like flame they emit and " parrots," by the Scotch miners, from the sparkling and crackling way in which they fly off in splinters when first thrown on the fire. Sometimes they occur in independent seams, but not unfrequently they form the upper portion of a splint coal, or even of a bed of blackband ironstone. Geo- logically, they seem to have arisen from a more thorough maceration of the vegetable mass, and under such conditions * In some of the towns of Bohemia, where gas is made from lignite, a small proportion of ordinary coal is added', and this improves the coke without de- teriorating the quality of the gas. LIGHT-PRODUCERS. 1/9 as permitted of a more equable bituminisation than ordinary coal. Their maceration is proved by the remains of shells and fishes (teeth, fin-spines, bones, and coprolites) which many of them imbed ; and further, by the fact that they sometimes pass into coaly blackbands, and, vice versa, coaly blackbands into cannels. While eminently gas-producers of the finest quality, the main objection to these coals by the gas-manufacturer is that they yield an inferior coke, and often no coke in the proper sense of the term, but a soft pulverulent residue of carbon and clay. Before the introduction of coal-gas these cannels were all but rejected, but since then they have gradu- ally risen in demand ; and what fifty years ago was scarcely worth 55. a ton are now selling at 255. and 305., and even at higher figures. Several of these cannels those of Wigan in Lancashire, Wellsgreen in Flintshire, Lesmahagow in Lanark- shire, and Wemyss and Capeldrae in Fife have a high repu- tation as gas-producers, though none of these can compete in cubic feet per ton with the brown " boardy" cannel of Boghead, Bathville, and Torbanehill in Linlithgowshire, which is now all but exhausted, and in 1873 brought as much as 4 per ton for paraffin purposes. As a general rule, however, the larger the amount of gas the more worthless the coke ; hence the objection of the gas-manufacturers to these rich cannels, and hence also the common practice of mixing them with poorer and better coking varieties. The following tabulation exhibits some of the better known cannels, and their average yield of gas per ton : Boghead or Torbane Mine Methil or Pirnie, Fifeshire, Overtown, Lanark, . Capeldrae, Fifeshire, Rocksoles, Lanark, . Kirkness, Kinross-shire, Lesmahagow, Lanark, Adamhill, Ayrshire, . Rigside, Lanark, ral, . 14,880 cubic 13,000 12,500 11,900 1 1, 800 n,68o 11,600 11,500 Wellsgreen, Flintshire, Wemyss, Fifeshire, . Arniston, Mid-Lothian, Skatrig, Lanark, - 11,400 11,000 10,800 10.400 Lochgelly, Fifeshire, . . .9,500 Such are the Heat and Light Producers obtained from the crust of the earth. They are all of vegetable origin, and differ in structure, texture, and composition, partly according to the conditions under which they were accumulated, but chiefly according to their age and the amount of mineralisation they have undergone. As we have already shown, there is a ISO HEAT AND LIGHT PRODUCING MATERIALS. gradual passage from existing vegetable growths to peat, from peat to lignite, from lignite to coal, and from coal to anthra- cite. It is thus that the coal family presents so many varieties, and that these varieties, in the distillation or metamorphism they have undergone or are still undergoing, produce so many hydrocarbons both in the gaseous, the liquid, and solid con- ditions. They occur in every formation, but it is chiefly in the older systems that they acquire their greatest thickness, compactness, and regularity. Many coal-fields are no doubt unknown, many are being worked, and many are wellnigh ex- hausted ; and considering the rapidly increasing consumption * in an age so thoroughly mechanical as the present, every care should be taken not only to utilise these fossil fuels and light- producers by the most economic methods, but to see that they are extracted from the crust to the utmost extent compatible with surface amenity and the safety of the miner. See Chap- ter VIII. on " Mine Engineering." The subjoined table, from Hunt's * Mineral Statistics,' shows the amount of coal raised during the year 1872 from the vari- ous coal-fields of England, Scotland, and Ireland : Tons. North Durham, Northumberland, and Cumberland, 13,010,000 South Durham, . . . . . . 17,395,000 Yorkshire, "\ Derbyshire, f Nottinghamshire, V . > ". . . 10,657,100 Warwickshire, I Leicestershire, / South Staffordshire and Worcestershire, . . 10,550,000 North Staffordshire, ) Cheshire, [ . , .^^ . . . . 6,327,188 Shropshire, ) Lancashire, North and East, ... . . 9,363,236 West Lancashire and North Wales, . . . 9,000,000 Gloucestershire, ) Monmouthshire, > . . . .- . . 7,000,000 Somersetshire, ) South Wales, . '. ; Glasgow (J. Brown) ; /, Dowlais, South Wales (E. Riley) : a b c d e / Silica, . Alumina Potash Soda 63-30 23-30 51,80 30.40 trace 51.10 31-35 55-30 27-75 2.19 0.44 66.10 22.54 67.12 21. 18 2.O2 Lime 0-73 o.zo 1.48 1-^4 0.67 O 7^ 1.42 trace 0.32 0.84 Iron oxide, . . , Water, combined, i. 80 4.14 4.63 *< 2.01 5-34 3.14 I-8 5 4.82 Water, hygroscopic, Organic matter, 10.30 13.11 10.47 10-53 1-39 O.QO 99-43 99-95 100.57 99.64 98.54 100.44 The fire-clays are raised by the same shaft as the coal, un- less when their outcrop comes to the surface, and then they are obtained by open workings.' They usually vary from one to O 210 REFRACTORY OR FIRE-RESISTING SUBSTANCES. four or five feet in thickness, and occasionally the thicker beds contain a band or bands of stone. A good fire-clay should have a uniform texture, a somewhat greasy feel, and be free from any of the alkaline earths. When properly ground, pugged, and mellowed, it is fit to be worked into any form and to be baked without showing either crack or distortion. The following account of the manufacture at Stourbridge, from Lieut. Grover's Report on Fire-clay Goods in the International Ex- hibition of 1871, shows well the method and process of treat- ment: "The clay is first exposed in spoil heaps over as large an area as can be secured, for from three to eighteen months, according to the state of the weather. The action of frost, as with ordinary brick-earth, is of great service in disintegrating the compact tough lumps of clay, and in dry weather the clay is frequently watered. In very wet weather three months' ex- posure will suffice for its proper mellowing or ripening, and it ultimately slacks and falls to pieces. After sufficient weather- ing, the clay is ground in circular pans by heavy stone-rollers shod with iron rims. Being ground, the clay is carried on an endless band to a ' riddle ' of about 4 or 6 mesh to an inch for fire-bricks, 6 or 10 for fine cement-clay, and 12 or 14 mesh for glass-house pot-clay the larger-sized mesh being used for the sifting of the clay in wet weather. The large particles that will not pass through the riddle are carried back on an endless band to the pan, and there reground. As a general rule, it is only for very large fire-brick lumps, that reground pots, cru- cibles, or bricks locally termed ' grogg ' are added to the clay before grinding ; and fire-cement clay is always ground pure. After passing through the riddle, the clay is tempered or brought to a proper degree of plasticity by the addition of water. It is then thoroughly stirred and kneaded in a circular iron pug-mill, by revolving knives projecting from a circular shaft driven by steam-power. The clay is forced down by the obliquity of the rotating knives, and streams slowly from a hole near the bottom, whence, being cut by wires into the proper forms, it travels on in an endless band to the moulding- sheds. The bricks are then moulded by hand in the usual manner, and dried at a temperature of 60 or 70 degrees in sheds heated by flues. In fine weather, however, the sun's heat is made to economise fuel. The bricks are burned in circular-domed kilns or cupolas, locally termed ' ovens,' where they remain from eight to fourteen days under gradually increasing temper- ature, which amounts to white heat for three or four days. They usually require seven days to cool down the heat being gradually withdrawn as it was gradually raised." PREPARED SUBSTANCES. 211 The uses to which fire-clay is applied are very varied, and extensive as varied fire-bricks, linings for furnaces, grate- backs, soles for ovens, chimney-flues, gas-retorts, coke-ovens, crucibles, glass smelting-pots, safes, garden-borders, vases, statuettes, and the like, being among the more abundant manufactures. Many of these are of great beauty and sym- metry, and all but indestructible by fire; while sewage- pipes, when thoroughly glazed and carefully laid, afford by far the best material for the purpose which modern science has invented. Indeed, so far as experience goes, there is nothing so durable, so clean and sweet, or so easily flushed as well- made, well-glazed, fire-clay pipes ; and thus, for sanitary uses, they stand unrivalled. The old-fashioned, square, stone-built drain required a large amount of water to flush it, decayed in course of time, leaked, and became a refuge to rats : the pipe- drain (circular or elliptical) is flushed by a mere trickle of water, endures for generations, and gives no harbour to vermin. In some manufactures (crucibles, furnace-linings, and the like) the clay is mixed with small and varying proportions of graphite, coke-powder, quartz -sand, and metallic oxides, ac- cording to the purpose in view, and occasionally an admixture of "cement" or "grogg" (old fabrics reduced to powder) is found to be of advantage. We have no statistics of the quantity of fire-clay annually raised in Britain; but considering the number of works in Staffordshire (about twenty), in Durham, in Lanark, and other places, it must amount to many thousand tons, and is still on the increase. According to Hunt's 'Mineral Statistics,' the quantity of clay, fine andyfo?, raised in Britain during the year 1872, was estimated at 1,200,000 tons value, ^450,000 ; and of this the fire-clays must constitute no inconsiderable amount. Silicious Sands. The celebrated Dinas bricks of Glamorganshire may be regarded more as artificial standstones than as bricks in the ordinary sense of the term. They are fabricated from material obtained from the vale of Neath, and, according to Dr Siemens, are the only substances practically available on a large scale, which he has found, capable of resisting the intense heat (4000 Fahr.) of steel-smelting furnaces. Analyses show them to consist of silica, 95.98; alumina, 1.20; lime, 2.15; magnesia, 0.24; iron oxide, 0.48; and manganous oxide, traces. They are imitated in Germany (Wagner's Technology) by an admixture of pure quartz-sand and i per cent of lime. 212 REFRACTORY OR FIRE-RESISTING SUBSTANCES. Fossil-Flour. Another fire-resisting substance obtained from the earth, and occasionally fabricated into bricks, is "Fossil-flour? a mealy, silicious deposit consisting of the myriad-shields- of infusoria, or the frustules of diatoms. Mingled with a paste of clay or lime, as has been shown by Fabroni in Italy and Fouret in France, this substance can be fashioned into bricks so light as to float in water, and therefore well adapted for fire-proof purposes on board ship without sensibly increasing the weight of the vessel. Having been already noticed under "Fictile Arts" (Chapter X.), the reader is referred to that section for further details. Graphite. Graphite (so called from its use in writing-pencils, and known also as plumbago or black-lead from its appearance, though lead does not enter into its composition) is another refractory sub- stance, now largely used in the manufacture of crucibles. It consists almost wholly of carbon there being present in some specimens a small percentage of mechanically admixed iron oxide, with occasional traces of silica. It occurs chiefly in the primary or metamorphic rocks, in nests and stratiform masses, and is found abundantly in many countries United States, Canada, Scandinavia, Germany, Urals, Siberia, &c. in various degrees of purity and texture. In our own country unim- portant nests occur in the gneisses of the Scottish Highland?, and in trap-altered portions of the coal-formation ; but a very fine and valuable variety is found at Borrowdale in Cumber- land, running in vein-like form through trap-rocks which inter- sect the clay-slates of that locality. This vein has not been worked for years, but when mined yielded some choice blocks for the manufacturer of drawing-pencils. Commercially, graphite is used for making writing-pencils, for polishing, and other purposes to be noticed under other heads : here we advert only to its use in the fabrication of crucibles for metal smelters and refiners. For this purpose the graphite is finely ground, and two parts intimately mixed with one part of best fire-clay, and then moulded into the requisite size and form. This composition bears a high heat and sudden changes of temperature, and forms a clean, smooth- surfaced, and profitable crucible. For some purposes coke and old crucibles reduced to a fine powder are added to the admixture each maker preferring some composition of his own. Thus, the Berlin crucible consists of 8 parts in bulk of fire-clay and cement, 5 of coke, and 4 of graphite ; the Passau, NATURAL SUBSTANCES. 213 of 56 fire-clay, 34 carbon, 8 iron oxide, and 2 magnesia ; the Hessian, of fire-clay containing a little iron oxide and silicious sand; the Cornish, of the best Poole or Stourbridge clay, ground pots, and sand ; and the Birmingham glass-pots, of the best Stourbridge or Monmouth clay. Fire-clay suitable for crucibles " pot-clay " as it is termed is by no means abun- dant, and brings a high price, that in the Stourbridge seam selling at five times the price of the ordinary material Alum, &c. Among fire-resisting substances may be noticed the alum of commerce, the nature and preparation of which is described in Chapter XIV. Steeped in a solution of this salt, cloth, paper, and wood become almost incombustible at least do not ignite so readily, and when ignited, burn away slowly and with diffi- culty. "If alum and common salt," says Jackson ('Minerals and their Uses'), "are reduced to an impalpable powder, and mixed with spirits of wine, and several coats of this be laid upon the skin of the hand, a red-hot iron may be held without inconvenience. This is, in fact, the secret of the human sala- manders, or incombustible jugglers, fire-eaters, &c." As a check to the inflammability of light dresses worn by ladies, the solution of alum might be more extensively and advantageously employed* Other solutions have been recommended by chemists, such as magnesium sulphate and borax, ammonium sulphate and gypsum, and sodium tungstate all of which lessen the inflam- mability of fabrics, by enveloping their fibres with a thin coating, which prevents the escape of inflammable gases. II. NATURAL SUBSTANCES. Firestones. Any stone that stands heat for a considerable time without perceptible injury is entitled to the designation of a Firestone. The term, however, is usually applied to certain sandstones of the greensand, oolitic, and coal formations employed in the construction of ovens, glass-furnaces, and similar erections sub- jected to high and oftentimes to intermittent temperatures. The upper greensand of Kent and Surrey (Reigate) yields a stone of this description which was at one time much prized ; some of the soft yellow sandstones of the Tyne (Walker and Bellingham) have also been employed in furnace-structures ; and the sandstone of Craigenbank, near Borrowstounness, has been 214 REFRACTORY OR FIRE-RESISTING SUBSTANCES. shipped to St Petersburg for furnaces, ovens, and similar pur- poses. Such sandstones, however, are now all but superseded by fire-clay fabrics. The firestone of Nevada, U.S., is de- scribed as a light, porous, silicious rock, having a specific gravity of 1.49, capable of being sawn into blocks of any form, and able to resist intense and intermittent temperatures. Leckstones. Another stone occasionally employed in oven and furnace structures, but especially as oven-soles, is obtained from the traps of the coal-formation. The Leckstones, as they are called, are open, granular varieties of trap (old ash-beds), and when carefully selected and dressed, stand well the alternations of heating and cooling. We have seen them quarried in Fife and Linlithgow, but the cheaper and handier slabs of fire-clay have driven them, we believe, entirely out of the market. Petstone. Potstone, the lapis ollaris of the ancients, and so called from its use, is a soft magnesian or talcose rock, of a greenish-grey or leek-green colour, sectile, and capable of being fashioned into pots, vases, and other articles. Mineralogically, it is an uncertain admixture of talc, chlorite, asbestos, and the like, occurring in beds among the serpentines and crystalline rocks of various countries : in other words, coarse granular varieties of steatite or soapstone. Like most magnesian minerals, it is little affected by heat, and was early fashioned into pots and pipkins pipkins, which had the property not only of being unaffected by changes of heat and cold, but of communicating no bad taste or quality to the food, and of being thoroughly cleaned by being heated red-hot. It is now seldom used for this purpose save in northern Italy and the Grisons ; but slabs of steatite are employed in Norway, Sweden, and America for furnaces, stove-linings, and ovens. It is also fashioned into gas-burners, which possess the property of not corroding, nor becoming clogged up, as is frequently the case with those made of metal. The Corsicans, it is said, use a fibrous variety, or asbestos (for both are nearly allied silicates of magnesia), in the fabrication of pots or pipkins, by mixing it with clay, and thereby obtaining a lighter and more durable vessel than could be obtained from the use of clay alone. Some talc-slates and gneisses also offer great resistance to high temperatures, and are occasionally employed in the con- NATURAL SUBSTANCES. 215 struction of reverberatory and other furnaces. Indeed, most silicio-magnesian rocks are endowed with this property, besides being readily cut and fashioned into any required form. Asbestos. Asbestos and Amianthus are the names applied by mineralo- gists to fine fibrous varieties of tremolite, actinolite, and other members of the hornblende family. They are all essentially silicates of magnesia, with a little lime, and traces of alumina, iron, manganese, and water. The fibres often readily separ- able, elastic, and flexible were used by the ancients in the manufacture of an incombustible cloth for the funeral pile; hence the name asbestos, inconsumable ; and hence also ami- anthtis, unsoilable, because the fabric when passed through the fire came out clean and unaltered. There are many varieties, and these receive their names from their appearance and quality as rock-wood, rock-cork, mountain-leather, fossil-paper, fossil-flax, &c. In rock-wood, the fibres are long, parallel, curved, and compact ; in rock-cork they have a felted texture, and so light as to swim on water ; in mountain-leather, they form flat flexible pieces ; and in fossil-flax they are so loose and silky that Dolomieu, when in Corsica, used it for packing his other minerals. Asbestos thus passes from the silky flexi- bility of amianthus to a degree of rigidity and compactness which admits of receiving a polish. It occurs among the meta- morphic rocks of many countries, and especially in connection with serpentine, which it traverses in irregular veins, varying from half an inch to two or even three feet in thickness the fibres being transverse to the cheeks of the vein. As a refractory or fire-resisting substance, it has been put to many uses : by the ancients, in the manufacture of incombus- tible fabrics, for funeral-pyre sheets, and for table-napkins ; and in modern times, for incombustible lamp-wicks, for filling gas-grates the fibres remaining red-hot without being con- sumedfor making fire-proof safes, and occasionally for manu- facturing indestructible paper. Recently it has been employed on a large and important scale in the manufacture of "-pack- ing" for steam-pistons, and of "paper-board" for the junction of steam-pipes, and the like. For these purposes it is obtained in large supplies from Italy, Corsica, the Tyrol, &c., in Europe, and from Massachusetts in America. The variety employed at the Asbestos Steam-packing Company's factory in Glasgow is obtained, we believe, from the north of Italy and Corsica, and is of a lamellar-fibrous texture, varying from three to 2l6 REFRACTORY OR FIRE-RESISTING SUBSTANCES. twenty or more inches in length. Being exceedingly tough, it is first broken into pieces by sledgehammer, then passed through corrugated rollers to soften it, next put through a teasing-machine and reduced to flossy fibres, and ultimately passed through a mill which slightly twists it into strands, en- closing these at the same time in a sheathing of pack-thread to give them greater consistency. In this state it is ready for the mechanical engineer, and is reported to stand longer than any other material yet employed as steam-packing. The paper-board is felted into sheets of various dimensions, whose thickness varies from that of a sheet of writing-paper to that of the heaviest pasteboard, and makes one of the handiest sub- stitutes for lutings that has ever been adopted. The substances noticed in the preceding pages are of vital importance to the Arts and Manufactures. They are essential in all our smelting and refining furnaces ; in our grates, hearths, flues, and chimneys ; in our gas and oil distilleries ; in our baking, pottery, and glass ovens ; and, in fact, wher- ever intense or long-continued heat has to be resisted. One of their main recommendations is that they are all abundant, easily obtained, and readily manipulated. Their supply is equal to any demand, and there is practically no limit to the forms or modes in which they can be applied. Considering their cheapness and abundance, and the frequency of destruc- tive fires in factories and warehouses, it seems culpable that they are not more extensively employed as floorings, parti- tions, linings, and even roofings their lightness, and the exactitude with which they can be shaped and fitted together, rendering them nearly as convenient as wood, without its liability to combustion. XIII. PIGMENTS, DYES, AND DETERGENTS. THE substances noticed under the present head are intimately connected with the Arts and Manufactures, both in the way of utility and ornament. The pigments when well prepared and carefully applied, are the best preservations of wooden and metallic structures ; the dyes give beauty and colouring to fabrics otherwise tame and uninviting ; and the detergents are essential to cleanliness and health. It is true that pig- ments, dyes, and detergents are obtained from the vegetable and animal as well as from the mineral kingdom ; but those from the latter have a brilliancy, permanence, and abundance which do not belong to those of the former. These sub- stances early attracted the attention of mankind the savage smearing his body with ochre, daubing his robe with reddle, or washing himself with magnesian clay, seeking, only in a ruder way, the same effect as the man of civilisation and re- finement by his most costly colours and detergents. Few of these substances can be applied in their natural state ; most of them have to undergo treatment and preparation ; and some of them can only be obtained in perfection by intricate chemical processes and manipulation. It is more, however, with the raw materials that we have here to deal their mineral characters and geological positions the processes by which they are brought to their finished state being altogether technological. i. PIGMENTS. " By paints," says Wagner, in his ' Handbook of Chemical Technology, " we understand substances which, as a rule, are insoluble in water, and are mixed with either weak glue solu- tion, being then termed water-colours, or with linseed-oil, called oil-paints. To these pigments belong white -lead, red -lead, 2l8 PIGMENTS, DYES, AND DETERGENTS. ultramarine, Berlin blue, vermilion, chrome -yellow, bone- black, &c. The ordinary water-colours are insoluble in water, being finely suspended therein by the aid of gum, white of egg, &c. The pastel pigments used for drawing are made up of various colouring matters mixed with pipe-clay, soap, and gum - tragacanth mucilage, and moulded into cylindrical sticks." Mineral Pigments. Among the most common and abundant of these pigments or colouring matters are the hydrated oxides of iron, known as ochres, boles, reddles, and the like. Strictly speaking, ochre (Gr. ochros, yellow) is a hydrated peroxide of iron, con- sisting of about 80 of the hydrate and 20 of water; but it is very rarely found pure, being often, in fact, clay coloured yellow by hydrate of iron, though a fair ochre should not contain less than 15 or 20 per cent of the hydrate. Naturally it varies from pale yellow to a deep orange or brown; but the manufac- tured article is usually toned to any shade by treatment and ad- mixture. It occurs in all formations; much of that used in Britain being obtained from the coal-formation, where it appears as a product of decomposition. Bole (Gr. bolos, a clod) is the term usually applied to friable clayey earths coloured by the per- oxide of iron, and varying from yellow to yellowish-red and reddish -brown. The term is rather an indefinite one, and loosely applied ; but a useful variety may consist of about 3 2 silica, 28 alumina, 21 iron peroxide, and 17 water. A variety from Cape di Bove yielded to C. von Hauer 45.64 silica, 29.33 alumina, 8.88 iron peroxide, magnesia a trace, and water 14.72 ; while another from New Holland gave 38.22 silica, 31.00 alumina, 11.00 iron peroxide, traces of lime and mag- nesia, and 1 8. 8 1 water. Bole occurs in irregular beds and disseminated masses in various formations, some of the finest sorts (Sinopian earth) being procured from Italy and Asia Minor. The better-known varieties are the Armenian, of a bright red colour ; the Sinopian, of a deeper red ; the Bohemian, of a yellow red ; the Blois, of a pale yellow ; the French, of a pale red ; the Lemnian, of a yellowish red ; and the Silesian, of a similar but brighter hue. Reddle, which is merely a corrup- tion of red-clay, is another of these argillaceous hydrated per- oxides of iron, usually of a deep red, and, in fact, a decom- posed haematite. It occurs abundantly in England, France, and Germany, and usually in the haematite-yielding districts of the carboniferous limestone, as Cumberland, north Lanca- shire, Somerset, and Devon. PIGMENTS. 219 All these substances are prepared for the colour-merchant by grinding, washing, and drying ; and the desired shade of colour is obtained by admixture. Another closely allied colouring material is Umber, which presents various shades of brown, and which occurs either naturally in veins or beds, or is prepared artificially from vari- ous admixtures. The " umber " proper of the mineralogist is a soft earthy combination of the peroxides of iron and manga- nese, with minor proportions of silica, alumina, and water 48 iron peroxide, 20 manganese peroxide, 13 silica, 5 alumina, and 14 water. It is usually found in veins in the crystalline schists, and appears to be a product of decomposition. Commercially it is obtained from the island of Cyprus, Anglesea, Isle of Man, Forest of Dean, and other localities. Much of the umber of the colourman, however, is merely an ochraceous admixture ; and that from Cologne is said to be only brown lignite finely pulverised. Some idea of the value of these ochres and umbers may be formed from the fact that in 1872 upwards of 3300 tons (worth ^8240) were raised from Anglesea, Devon, Cornwall, and the Isle of Man. Whiting, or Spanish White, one of our most common but use- ful colouring matters, is obtained from the softest and purest white chalks by grinding and elutriation. It is extensively used as a whitewash ; and occasionally, when carefully and deli- cately prepared, as a cheap white paint. A serviceable white- wash for external walls, and one possessing disinfecting proper- ties, is obtained by diluting quicklime the purer and whiter the limestone, the more brilliant the whitewash. Coloured washes and rubbing bricks for external use have usually a basis of whiting or clay, the basis being obtained from ochre, reddle, bluestone, or other cheap material. Ultramarine (literally "beyond the seas," from its being brought from China and Further Asia), so highly esteemed for the extreme beauty, softness, and durability of its fine azure- blue, was originally prepared from the lapis lazuli. This mineral, which occurs in the old crystalline schists and limestones (see Chapter on "Precious Stones"), is rather rare, and after treatment yields only a small percentage of the colouring matter hence the former high price of the pigment. From analyses of the stone, which consists of 45.40 silica, 31.67 alumina, 9.09 soda, 5.89 sulphuric acid, 3.52 lime, 0.86 iron, 0.42 chlorine, and o.i 2 water, Gmelin, in 1822, was led to attempt its artificial 220 PIGMENTS, DYES, AND DETERGENTS. production. His experiments were successful; but not till many years after was ultramarine produced on a commercial scale, though now as much as 180,000 cwt. are annually manu- factured in Europe, at a mere fraction of the price of the natural product. The artificial pigment can be made to rival the natural in beauty and softness, at the same time that it admits of a greater variety of shades and tonings. It is manufactured prin- cipally in Germany and France, and consists of definite propor- tions of kaolin or silicate of alumina, calcined sulphate of soda, calcined soda (sulphuret of sodium is a by-product of the manu- facture), sulphur, and pulverised charcoal or pit-coal other in- gredients, as gypsum, baryta, &c., being added to tone the colour to special requirements. Different manufacturers adopt differ- ent methods and proportions ; but the following may be taken as an example of the composition of the artificial pigment : 46.60 silica, 23.30 alumina, 3.83 sulphuric acid, 21.48 soda, i. 06 iron peroxide, with traces of lime, sulphur, and magnesia. Ultramarine is largely employed as a paint, as a pigment for paper-hangings, in calico-printing, for colouring printing-ink, for the bluing of linen, and for imparting blue tints to various fabrics; and is said to be rapidly superseding smalt, litmus, and Berlin blue. Metallic Pigments. A great many pigments are prepared from the metals lead, zinc, copper, cobalt, chromium, arsenic, iron, manganese, mer- cury, &c. ; but as the processes are purely technological, they belong to chemistry rather than geology. The metals, no doubt, belong to the mineral kingdom, and will be treated in other Chapter (XVIII.); but all the reductions, manipulations, and admixtures by which they are converted into colours of unrivalled brilliancy and durability, are matters that lie beyond the domain of the geologist. In illustration, however, of their importance as colour-producers, we may adduce a few examples : From lead we obtained massicot or the yellow oxide, litharge, red-lead, and white-lead ; from chromium and lead, chrome- yellow, chrome-orange, and chrome-green; from cobalt, smalt or cobalt-blue, cobalt-ultramarine, cobalt-green, and cobalt- bronze ; from zinc, zinc-white ; from copper, Brunswick green, mineral green, emerald green, Bremen green and blue, and the like; from mercury, vermilion; from gold, purple of Cassius; from antimony, orange, Neapolitan yellow, and vermilion-red ; from arsenic, realgar and orpiment ; and from iron and manganese, various tints of black, red, brown, and yellow. Indeed it is PIGMENTS. 221 from the metals that we obtain the majority of our most brilliant and durable pigments ; and chemistry is every year inventing new methods and producing new colours the art of the colour- manufacturer being at once one of the most subtle and suc- cessful. The subject, perhaps, may be rendered "more obvious by tabulating the colours and the mineral and metallic sources from which they are derived : White pigments, from lead, zinc, heavy-spar or sulphate of baryta, chalk, and admixtures. Yellow pigments, from antimony, lead, arsenic, chromium, chalk, and admixtures. Orange pigments, from ochre, chromium, lead, chalk, and admixtures. Brown pigments, from umber, Terra di Sienna, manganese, and admix- tures. Red pigments, from ochre, bole, reddle, chrome, mercury, arsenic, lead, and admixtures. Black- pigments, from iron, manganese, asphalt, coal-tar, and admixtures. Blue pigments, from cobalt, copper, iron, lapis lazuli, potash, soda, and admixtures. Purple pigments, from gold and tin, and from admixtures. Green pigments, from copper, chrome, arsenic, potash, and admixtures. Intermediate shades, like compound colours, are all obtained by skilful admixture the produce, in fact, of the chemist and technologist. Pastel Pigments. As already mentioned, pastel pigments for writing, drawing, and marking, consist of colouring matters worked up with pipe-clay, steatite, soap, and various gums, to give them body and consistency. Writing and drawing pencils, drawing- chalks, lithographic chalks 1 and the like, belong to this class of materials. Some of them, like the common black-lead pencils, consist of native mineral substances ; others, like the coloured crayons, are manufactured admixtures. Their pre- paration is wholly technical ; we only allude to the minerals which enter into their composition. Formerly, black-lead pencils were sawn from the finer varieties of graphite, like that of Borrowdale in Cumberland ; but now the great majority of those in ordinary use are manufactured from graphite finely triturated, and then compressed into blocks in imitation of the native mineral the various shades of B, BB, HB, &c., being brought out by admixture and treat- ment. The Borrowdale mine having been closed for many years, the Keswick pencils, like others in the market, are now chiefly made from the manufactured material. For the com- position, modes of occurrence, and other characteristics of 222 PIGMENTS, DYES, AND DETERGENTS. graphite, which is found in the metamorphic rocks of many countries, the reader is referred to Chapter XII. Coloured Crayons or Drawing-Chalks. Red, blue, and other tints are chiefly made of fine pastes of pipe-clay, china-clay, or steatite, intimately mixed with earthy or metallic pigments. Some of these so-called chalks, however, are natural products, such as Red chalk, a clay or reddle containing from 15 to 20 per cent of iron peroxide ; Brown chalk, a fine variety of umber ; Black chalk, a variety of carbonaceous drawing-slate ; and French chalk, a variety of steatite or soapstone. Lithography. While speaking of chalks and crayons, we may appropriately advert to the limestones fitted for the purposes of Lithography, and which also come under the domain of Economic Geology. Though attempts have been made to utilise some of our own liassic and oolitic limestones, the slabs of the best quality are still obtained from the quarries of Solenhofen, near Munich, where the art of lithography had its birth. There, and throughout Pappenheim, on both sides of the Danube, litho- graphic slabs of all sizes and qualities can be obtained from the flaggy oolites. Good serviceable stones have usually a yellow or bluish-grey colour, are compact and uniform in tex- ture, and free from veins, flaws, and spots, that would interfere with the delicate lines of the lithographer. The quarrying, dressing, and polishing of lithographic slabs for home use, and their exportation to all parts of the world, has of late years become an important branch of industry in Upper Germany. Varnishes. Closely related to the pigments are the varnishes com- pounds which are spread over the surface of any body to give it a shining, transparent, and hard coat, capable, more or less, of resisting the action of air and moisture. The great major- ity of the varnishes employed by cabinetmakers, japanners, tanners, and others, are solutions of gums, resins, and wax in alcohol, turpentine, oils, and the like, and consequently lie beyond the domain of Geology. A few, however, are prepared from amber and asphalt the former forming a very hard and durable varnish, the latter being the main ingredient in most of the black or Japan varnishes. DETERGENTS. 223 II. DYES. " Dyeing," says Wagner, " is distinguished from painting by the fact that the pigments are fixed to the animal and vege- table textile fabrics according to certain physico-chemical principles, and are not, as in painting, simply fixed by ad- hesion to the surface, although painters and artists occasionally use the same pigments. Printing consists in the duplication of coloured patterns, and is a very important part of dyeing. In the art of dyeing, some colouring matters are applied by immersing the tissue to be coloured in the decoction or solution of the pigment. Some substances are applied to the surface of the woven fabric by the intervention of what is termed a ' mordant,' which secures the adhesion, fixing, and permanency of the colours." The great majority of dyes and dye-stuffs are obtained from the vegetable kingdom ; some from the animal ; and, till re- cently, only a few from the mineral. Though these are chiefly of organic origin, the " mordants," or substances employed in fixing or striking their colours, whether in woollen, silk, cotton, or linen, are all, or nearly all, of inorganic origin such as acetates of iron, lead, and alumina, sulphates of iron and alumina, aluminate of soda, and alum. In this way the art of dyeing comes within the range of Economic Geology. Of recent years, however, the relationship has become more intimate, and by the researches of modern chemistry we now derive from the inorganic world a variety of dyes of unsur- passed beauty and brilliancy. Strange as it may seem, these are chiefly obtained from coal-tar a dark, dingy, and uninvit- ing by-product of our gas-works. Chemically treated, by a number of ingenious processes this substance yields the aniline or coal-tar colours of commerce fuchsin, magenta, aniline blue and violet, Manchester yellow, aniline orange and aniline brown, coralline, alizarine, Magdala red, and aniline black. Few triumphs of chemistry have been more marvellous than the production of these beautiful colours no substances so unlike as a mass of pitchy coal-tar, and the brilliant flush of roseine, mauve, and magenta. III. DETERGENTS. Fuller's Earth. One of the best-known and abundant of mineral detergents is fuller's earth or fuller's clay, so called from its being em- 224 PIGMENTS, DYES, AND DETERGENTS. ployed in the fulling of woollens. In composition it is some- what varied ; but all the varieties are soft, unctuous, hydrous silicates of alumina that of Reigate, from the greensand of Surrey, consisting of 53 silica, n alumina, 24 water, and 9 iron oxide, with traces of magnesia and lime. Good fuller's earth is usually massive, opaque, soft, dull, with a greasy feel and an earthy fracture ; scarcely adheres to the tongue ; and when placed in water, falls down to an impalpable powder without forming a paste with it. It occurs abundantly in the oolitic and cretaceous systems of England, in beds from one to several feet in thickness, and of a greenish or greyish-green colour. So important at one time was this earth to the woollen manufacture of England, that its exportation was prohibited by Act of Parliament. Its place is now mainly supplied by soap and other chemical detergents, though considerable quantities are said to be still dug and -prepared for the fuller in Surrey, Gloucestershire, and Bedfordshire. Besides being used by the fuller, under the names of fuller's earth, Walker's earth or walkerite, and smectite (Gr. smectep, a cleaner) it is also em- ployed in paper-making, and as an addition to artificial ultra- marine. Nowadays the principal detergents, whether employed in woollen, silk, cotton, linen, or leather manufacture, are of chemi- cal preparation soaps, leys of soda and potash, chlorine, chloride of lime, &c. and as far as the limes, alkaline salts, and soluble silica (which enters into the composition of some soaps), are concerned, come under the cognisance of Geology. The operations of washing, bleaching, and tanning are all more or less facilitated by preparations obtained wholly, or in part, from the mineral kingdom. The same may be said of sugar- refining, in which lime, gypsum, and baryta are now success- fully employed, not only in producing a purer article, but in facilitating the operation. As explained in the preceding pages, most of the pigments, several of the dyes, and many of the detergents, are obtained either directly or indirectly from the mineral kingdom, and in this way come within the scope of Economic Geology. The elaboration of these substances belongs more especially to chemistry ; but to the working geologist is left the discovery of the raw materials, their modes of occurrence, abundance, and the facility with which they can be procured. Many of them have long been known ; but some are the results of recent re- search, and hold out the hope that others may yet reward the skill and industry of the diligent inquirer. The earth is a DETERGENTS. 225 vast storehouse of mineral and metallic wealth, only awaiting the requirements of man, and the skill to utilise them ; and the geologist best performs his function, when in conjunction with the chemist and technologist, he is ever on the watch for new products and more advantageous appliances. Numerous, beautiful, and useful as our pigments, dyes, and detergents un- doubtedly are, it cannot for a moment be supposed that we have either exhausted the field of their variety, or the sources from which they are derived. The artificial preparation of ultramarine, and the discovery of the coal-tar or aniline colours, are apposite cases in illustration, and hold out the in- centive alike to chemist and geologist to persevere in their researches for results equally successful and satisfactory. The discovery of mineral substances has not been exhausted, any more than the limits of invention have been reached, by those who have gone before us. Works which may be consulted. Wagner's 'Handbook of Chemical Technology' Crooke's Edition ; Ure's ' Dictionary of Arts and Manufactures ' Hunt's Revision ; Knapp's 'Chemical Technology' vol. ii. ; Watt's 'Dictionary of Chemistry. ' XIV. SALTS AND SALINE EARTHS. BY the Salts and Saline Earths we mean those substances which, like rock-salt, natron, and nitre, are obtained from the rocky crust, either in a crystallised state comparatively pure, or so associated with earthy matters as to require chemical processes of extraction and purification. These substances play im- portant parts in the arts and industries in domestic economy, in medicine, agriculture, bleaching, dyeing, glass - making, powder-making, glazing, enamelling, and various other pro- cesses. Some, like rock-salt, occur in stratiform masses j some are obtained by the evaporation of saline waters ; and others, again, are found commingled with sand, gravel, and earthy debris, in the sites of desiccated lakes, deserted sea-lagoons, and old upraised sea-beaches. Many of these salts are hydrous, that is, they contain a definite proportion of water of crystal- isation ; others are destitute of water, and are dry or anhydrous salts. Some attract moisture when exposed to the air, and are said to be deliquescent ; others suffer their water to escape, and become opaque and pulverulent, and are said to be efflorescent. They are all more or less soluble in cold water, and much more easily so in boiling water forming brines and saturated solu- tions. Whatever their characteristics, they are easily treated, and many of them are produced on the large scale by artificial processes. I. SALTS OF SODA. Foremost among these, both in point of bulk and import- ance, is Rock-salt, common salt, or chloride of sodium, 60.4 chlorine and 39.6 sodium. This mineral occurs as an efflor- escence in most of the salt-deserts of the world, in old sea- reaches, and on the shores of salt-lakes. It is thrown up in solution by saline springs, and forms a principal ingredient in the waters of the ocean. It is also found as a rock-mass SALTS OF SODA. 22/ in several formations, often in a state of considerable purity, but more frequently coloured by iron oxides and commingled with earthy impurities. In its purest state it may consist of 98 or 99 of chloride of sodium, with traces of chloride of mag- nesium, sulphate of lime, chloride of calcium, and insoluble matter the rock-salt of Chester yielding to Henry 98.3 chloride of sodium, 0.05 chloride of magnesium, 0.65 sulphate of lime, and i of insoluble ingredients. In its impure con- dition it may contain from a sixth to even a half of earthy admixtures. Pure chloride of sodium is not liable to deliquesce, but it rapidly attracts moisture from the air when it con- tains chlorides of magnesium and calcium. In the British Isles the great repository of rock-salt is the Trias, or Upper New Red Sandstone (Cheshire, Middles- borough, Antrim) ; but deposits of equal magnitude are found in connection with oolitic strata, as in the Salzburg Alps with cretaceous greensands, as at Cordova in Spain with chalk and tertiary rocks in the Valley of Cardona in the district of the Pyrenees with tertiary marls, as in Sicily and at Wielitscka in Poland ; and salt or brine springs are known to issue from carboniferous and older strata. It is thus a product of all epochs, and must have been formed either by the gradual and long-continued desiccation of limited areas of salt water alter- nately cut off and placed in communication with the ocean, or by precipitation from saturated solutions, brought about, perhaps, by the evaporating power of volcanic or other thermal agency. The Cheshire deposits of rock-salt, which may be taken as a typical illustration, lie along the line of the valley of the Weaver, in small patches, about Northwich. There are two main beds lying beneath 120 feet of coloured marls, sands, and irregular bands of salt and gypsum, in which no traces of animal or vegetable fossils occur. The upper bed of salt is 75 feet thick ; it is separated from the lower one by 30 feet of coloured marls, sands, and salt-bands, similar to the general cover : and the lower bed of salt is above 100 feet thick, but has nowhere been perforated. They extend in an irregular oval area, about a mile and a half in length by three-quarters of a mile in breadth. The salt in these deposits is in some por- tions pure and transparent, and in others of a dirty reddish hue, and mixed to the amount of half its bulk with earthy im- purities. It is not stratified nor laminated, but divided into vertical prisms of various forms and magnitudes, sometimes more than a yard in diameter the outer sides of these rude crystallisations being generally pure and transparent. s 228 SALTS AND SALINE EARTHS. Rock-salt is seldom sufficiently pure to be crushed for direct use, but has to undergo lixiviation and preparation. Occa- sionally it is more economical to pump the brine; from old mines and salt-springs and evaporate, than to raise the solid mineral. Indeed, the sands which alternate with the marls and salt-beds are saturated with brine, and in several localities are the chief sources from which the salt is obtained. The preparation of salt from sea-water (bay-salt), at one time so largely carried on in Britain, is now little if at all resorted to, and where practised is often facilitated by the addition of rock-salt to the natural brine. In tropical and sub-tropical countries, however, a large amount is still prepared, partly by natural and partly by artificial evaporation. The great centres of the salt industry in Britain are Cheshire and Wor- cester the mines of the former, and the brine-pits of the latter, not only supplying almost the whole of the home consumption, but exporting annually nearly 800,000 tons (747,803 in 1872) to all parts of the world, at a value of ^"592,100! In 1872, the total quantity of salt returned as made in the United Kingdom, amounted to 1,309,497 tons. In 1873, the amount of rock-salt and salt produced in Cheshire was 1,013,497 tons; in Worcestershire, 276,000 tons; and in Ireland, 20,000 tons quantities which show at a glance the extent and importance of this branch of mineral industry. The uses of salt in the arts and manufactures are at once numerous and important. Passing over its value as a condi- ment and antiseptic in domestic economy, it is largely em- ployed in agriculture and the manufacture of artificial manures, in the glazing of pottery and earthenware, in the preparation of soda r chlorine, and sal-ammoniac, in tanning, and in many metallurgical processes. Natron (Lat. natrium, soda), or hydrated carbonate of soda, is an abundant natural product, consisting of about 19 soda, 27 carbonic acid, and 54 water. It occurs in solution in the waters of many springs and salt-lakes (Germany, Egypt, Cen- tral Asia, &c.) ; as a crystallised incrustation on the beds of dried-up lakes, in deserted river-courses (Central Asia, Colom- bia, &c.) ; and in numerous salinas or upheaved sea-reaches (South America) ; as a pulverulent efflorescence on the ground, as in the plain of Debreczin in Hungary; and as a product of decomposition in many lavas and other volcanic rocks. In general it is found mingled with sand, clay, and other impuri- ties, from which it requires to be dissolved and evaporated to recover it in the crude crystallised form. At one time it was SALTS OF SODA. 22Q largely, and is still to some extent, prepared from the ashes (kelp, barilla) of -certain sea-plants ; but now the bulk of the soda of commerce is obtained by chemical processes from common salt, ' and minor portions, we believe, from cryolite, bauxite, and during the conversion of the nitrate of soda into the nitrate of potash for the manufacture of gunpowder. The amount of soda (caustic, carbonate, and bicarbonate) annually produced in Britain is said to exceed 400,000 tons. This salt is employed in bleaching, washing, dyeing, in the manufacture of soap and glass, and for numerous industrial purposes. Trona (Arabic), or the native sesquicarbonate of soda, is found in similar situations, and employed for similar purposes as the preceding salt. It consists of about 37 soda, 38 carbonic acid, 2.5 sulphate of soda, and 22.5 water. Nitratine is the mineralogical term for nitrate of soda, which consists of 36.6 soda and 63.4 nitric acid. This salt, like the carbonates, occurs in many situations, but most abundantly in the salinas or desert saline tracts of South America. These salinas have been already noticed under Chapter III., and for their extent and richness are among the most wonderful re- positories of saline ingredients in the world. Nitrate of soda is largely used as a manure, and is employed .in the arts as a substitute for nitre ; but it is unfitted for gunpowder from its tendency to deliquesce. Glauber-salt (after Glauber, a German chemist) is the sul- phate of soda the sal mirabile of the older chemists, consist- ing of soda 19.3, sulphuric acid 24.8, and water 55.9. It occurs chiefly as an efflorescence in quarries and on old walls, as in the salt-mines of Austria, Spain, and other countries ; it is deposited in great abundance from the hot springs at Carls- bad, and is found in many other mineral waters ; and is like- wise procured from salt-springs, and forms a crust or efflores- cence on the borders of salt -lakes in Central Asia, Egypt, Southern Russia, the United States, and other regions. Glau- ber-salt is usually of a greyish or yellowish white colour, has a cooling and then a bitter saline taste, and is extremely efflor- escent. It is used in medicine. Glauberite, a nearly allied salt, and so called from its con- taining a large amount of Glauber-salt, is a sulphate of soda 230 SALTS AND SALINE EARTHS. and lime 5 1 sulphate of soda and 49 sulphate of lime ; or sulphuric acid 57.5, lime 20.1, and soda 22.4. Borax (Arab.), or Borate of Soda (boracic acid 36.5, soda 16.3, and water 47), is found associated with rock-salt in loose crystals among sands and clays on the shores of certain salt- lakes in Tibet and Nepaul, in Ceylon, South America, and California. Many springs also yield borax in small quantities, and according to G. E. Moore, the waters of Borax Lake in California contain 535 grains of crystallised borax to the gallon. In its crude or impure state it is known as tincal, and from this the pure borax of commerce is derived by several chemical processes. It is also made in large quantities from the boracic acid of the Tuscan lagoons. These lagoons occupy a large extent of surface, and consist of numerous fumeroles and springs in a violent state of ebullition. The vapours contain boracic acid, and by making these pass through reservoirs of water they impregnate the water with the acid. This impregnated water is then evaporated in leaden reservoirs by the heat of the vapours themselves, and leaves the acid in a state of crystallisation. By various processes the crystallised acid is combined with carbonate of soda (in the proportion of 38 of the former to 45 of the latter) to produce the borax of commerce. Boracic acid is also contained in the mineral Hayescine, known as boro-calcite or borate of lime (50 boracic acid, 18 lime, and 35 water), which occurs in incrustations near the Tuscan lagoons, and largely in the salinas of South America, where it is found as soft rounded nodules, from the size of a hazel-nut to that of a potato, having when broken up a silky, fibrous, radiated structure, of a snow-white colour. In this crude state it is imported into Britain under the native name of Tiza. Borax has a sweetish taste, affects vegetable colours like an alkali, effloresces and becomes opaque in a dry atmosphere, melts at a heat a little above that of boiling water, and gives out its water of crystallisation, forming a dry spongy mass known as calcined borax. Industrially, borax forms the most valuable re-agent for blowpipe purposes ; it is used in the preparation of fine glass and artificial gems, in enamelling, in soldering, as a flux in several metallurgical operations, and as an ingredient in cer- tain varnishes, in toilet soaps, and in cosmetics. The non- metallic element Boron, which is a dark greenish - brown powder, tasteless, and inodorous, is obtained by chemical treatment from boracic acid. SALTS OF POTASH. 231 Another rare and important salt of soda is Cryolite (Gr. kryos. ice ; lithos, stone), a double fluoride of sodium and alumi- nium, consisting of 13.10 aluminium, 33.27 sodium, and 53.63 fluorine. Hitherto it has been brought only from West Green- land, where it occurs with other minerals in gneiss in a vein about 80 feet thick, massive, and of lamellar structure. There are two varieties a snow white and a rusty yellow, and both are used as commercial ores of aluminium. II. SALTS OF POTASH. The most important of the potash salts is the nitrate known as nitre (Nitria in Egypt) or saltpetre (petra, a rock), from its occurring so frequently in connection with loose shingly soils. It consists of 46.6 potash and 53.4 nitric acid. " It is," says Brande, ' Diet, of Science/ " spontaneously generated in the soil, and crystallises upon its surface in several parts of the world, especially in India, whence nearly the whole of the nitre used in Britain is derived. It has occasionally been pro- duced artificially in nitre-beds, formed of a mixture of cal- careous soil and animal matter. In these nitrate of lime is slowly formed, which is extracted by lixiviation,and carbonate of potash added to the solution, which by double decomposi- tion gives rise to the formation of nitrate of potash and car- bonate of lime the latter is precipitated, the former remains in solution, and is obtained in crystals by evaporation." Nitre crystallises in six-sided prisms, is soluble in four parts of cold water, and in less than its weight of boiling water. It has a cooling taste, is antiseptic, and is not altered by exposure. At 616 it fuses, deflagrates vividly on burning coals, and detonates with combustible substances. " Nitre," says Dana, " requires for its formation dry air and long periods without rain ; hence its frequency in India, Persia, Egypt, Algeria, and Spain. The potash comes mainly from the debris of felspathic rocks in the soil, and the oxidation of the nitrogen of the air is promoted by organic matters ; hence the nitre is generally associated with nitrogenous decom- posed organic substances." * The potash salts obtained from superficial deposits, from kelp, sea-water, &c., are now inconsiderable compared with what are obtained by chemical processes from the natural deposits of Stassfurt in Germany. These deposits, which were discovered in 1851 and first worked in 1857, consist of a series of saliferous beds carnallite, kieserite, kainite, poly- 232 SALTS AND SALINE EARTHS. halite, common salt, &c. in bands of various thickness and purity, and all rich in salts of potash, soda, magnesia, and lime, These beds form a very complex series in the salt-formation of Germany, and are evidently the results of marine evapora- tion and deposition. F. Bischoff divides them vertically into four regions, corresponding, he observes, to the natural order of origin from an evaporating saline, viz., i, or lower, the anhydrite region; 2, the poly 'halite ; 3, the kieserite ; and 4, the carnallite. The kieserite is in beds from 9 to 12 inches thick, alternating wtih common salt. The whole deposit is about 190 feet thick, and has the following mean percentage composition : Common salt (chloride of sodium), 65; kieserite (sulphate of magnesia), 1 7 ; carnallite (double chloride of potassium and magnesium), 13 ; hydrated chloride of mag- nesium, 3 ; and anhydrite (sulphate of lime) 2 = 100. Similar compounds are found in the saliferous system of Kalutz in Hungary, and at the salt-mines of Maman in Persia. Nitre is largely employed in the arts in glas's-making, in medicine as a diuretic, in metallurgy as an antiseptic, and for producing nitric acid ; but especially, and most extensively, in the manufacture of gunpowder, lucifer-matches, detonating powder, and the like. III. SALTS OF MAGNESIA. The most abundant and best known of the magnesian salts is the sulphate, consisting of 16.26 magnesia, 32.52 sulphuric acid, and 51.22 water. It is generally known as Epsomite or Epsom salts, from the springs of Epsom in Surrey, in whose waters it forms the most notable ingredient. It occurs, how- ever, in many mineral waters (Seidlitz, Saidschutz, &c.), and as botryoidal masses and capillary efflorescences in old mines, veins, coal-workings, quarries, and caverns. It is a white lustrous salt, translucent and brittle, with a bitter saline taste. Though occurring abundantly in nature, the greater portion of the Epsom salts of commerce is manufactured either from the magnesian limestones of Durham and York, or from the white chalk-like carbonate of magnesia (Magnesite) imported from the Mediterranean, which is said to produce a finer and purer sample. The Magnesian limestones have been already noticed under Chapter V. Magnesite generally occurs in veins or in masses associated with serpentine, and consists of 5 1 magnesia, and 49 carbonic acid. The salts of magnesia are used chiefly in medicine ; and the earth itself in the preparation of the metal magnesium. SALTS OF ALUMINA. 233 IV. SALTS OF AMMONIA. The principal salt under this group is sal-ammoniac, or the muriate of ammonia, consisting of chloride of ammonium 99.5, and sulphate of ammonia 0.5, and so called from the temple of Ammon in Egypt, where it was originally extracted from the soot obtained by burning camels' dung. It is now largely produced by the destructive distillation of organic bodies containing nitrogen, but occurs native in crusts, stalactites, and pulverulent masses, chiefly in rents and fissures near active volcanoes, in the vicinity of ignited coal-seams, and in the guano of the Chincha islands. It is of a greyish or yellowish white, according to impurities of iron, sulphur, &c. ; has a saline pungent taste, is easily soluble in water, and volatilises without fusing. Sal-ammoniac is used in medicine, in dyeing, and in various metallurgic processes. The carbonate of ammonia (ammonia 32.9, carbonic acid 32.9, and water 55.7), and the sulphate of ammonia (sulphuric acid 53.3, ammonia 34.7, and water 12), are salts occurring in a crude or native state the former chiefly in connection with guano deposits, and the latter in the neighbourhood of vol- canoes, and as a product of the combustion of coal and the manufacture of gas and paraffin-oils. The crude sulphate can be obtained in large quantities from the ammoniacal water of gas and oil works ; in other words, from the distillation of bituminous shales, gas-coals, and peats the latter yielding, according to Sir Robert Kane, about 25 Ib. per ton. These salts are employed in the manufacture of sal-ammoniac, in the preparation of ammonia-alum, and, in their crude state, as stimulating manures. (Saline Manures, Chap. III.) V. SALTS OF ALUMINA. What are known as Alums are double salts that is, sulphates of alumina, with sulphates of potash, of soda, of ammonia, of magnesia, or of iron ; hence spoken of as potash-alum, soda- alum, ammonia-alum, magnesia- alum, and iron or feather alum. They occur in nature on the surfaces and in the chinks and fissures of many rocks in minute snow-like crystals, or in feathery efflorescences, but never in commercially available masses. They are extracted by chemical processes, and the rocks containing them in notable proportion generally manifest their presence when exposed to air and moisture, by emitting 234 SALTS AND SALINE EARTHS. whitish or yellowish-white efflorescences of the salts ; and these, as well as the water which trickles from the rocks, are readily detected by their sweetish astringent taste the taste peculiar to common alum. Alum is manufactured from certain transition slates (Nor- way), from coal-shales (Renfrew and Lanark), from lias-shales (Yorkshire), lignite-shales (Germany), and from alum-stone in the volcanic formations of Sicily ; hence such geological de- signations as alum-slate, alum-shale, aluminite, alum-stone, &c. For the extraction of the salts these aluminous earths are variously treated : some containing iron pyrites being merely exposed to the disintegrating effect of the air and moisture; others, void of pyrites, being roasted by the adding of brush- wood or coal-slack, during which processes the sulphur of the pyrites becomes converted into sulphuric acid, and sulphate of alumina is formed, together with sulphate of iron. Whether the ustulation is produced by the spontaneous combustion of iron pyrites or by the addition of fuel, a slow continued heat is always most favourable to the reduction of the alum-shales. The salts are extracted by digestion in water the iron sulphate is removed, and potash, soda, ammonia, &c., added to purified sulphate of alumina the salts of alum being obtained by subse- quent partial evaporation to saturation. Alum is also obtained by treating the Dorsetshire and other fine clays with sulphuric acid j but this is a process of technological rather than of geo- logical interest. Common alum is soluble in from 16 to 20 times its own weight of cold water, and in slightly more than its own weight of boiling water. Alum is used in medicine as an astringent, as an antiseptic, as a mordant in dyeing and calico-printing, in the manufacture of paper and leather, for rendering wood and cloth incom- bustible, and for various other purposes. The earliest centres of alum production in Britain were Whitby in Yorkshire, and Hurlett and Campsie near Glasgow ; but more recently large quantities have been produced by the sulphuric-acid process at works near Manchester, Goole in Yorkshire, and other places. A few thousand tons are annually imported ; but a larger amount is exported, the manufacture having of recent years assumed gigantic proportions. The alum of commerce is principally an ammonia-alum (alumina 11.90, sulphuric acid 35.10, ammonia 3.89, and water 48. 1 1) ; the potash-alum, which it has greatly superseded, consists of alumina 10.83, sulphuric acid 33.71, potass 9.95, and water 45.51 ; and soda-alum, of alumina 11.12, sulphuric acid 34.9, soda 6.8, and water 47.1. Aluminate of soda METALLIC SALTS. 235 (alumina 48, soda 44, and chloride of sodium and Glauber- salt 8) is also prepared on a large scale as a useful form of soluble alumina, especially in dyeing and calico-printing. Other salts of alumina are used in commerce the acetate as a mordant in calico-printing, and the sulphate as a substitute for alum ; but with the exception of the fact that the alumina is derived from the rocky crusts, their history and preparation have more of a chemical than of a geological interest. VI. METALLIC SALTS. Under this head are comprehended such salts as the sulphates of iron, copper, and zinc, familiarly known as copperas or green vitriol, blue vitriol, and white vitriol. These salts occur sparingly in a crude or native state, but are prepared on a large scale for the arts and manufactures. They are exten- sively and variously employed, and are amongst the most im- portant products of the manufacturing chemist. The sulphate of iron, familiarly known as copperas or green vitriol, is a salt occurring in various shades of green and greenish yellow, lustrous and brittle, with a strong metallic or astringent taste. It consists of sulphuric acid 28.9, protoxide of iron 25.7, and water 45.4. It is generally produced by the decomposition of iron pyrites in shales and clays, and is found in many situations and formations, though on a limited scale. As an artificial product it is produced on a large scale by moistening the pyritous shales (sulphides of iron), which are found abundantly in the coal-measures (Renfrew and Lanark), &c. ; exposing them to the air, when decomposition takes place, and the sulphide is converted into the sulphate of iron, which is subsequently dissolved and evaporated, to procure it in the crystallised state. Copperas is a valuable salt, and is extensively employed in dyeing and tanning ; in the manufacture of writing-ink, Prus- sian blue, sulphuric acid, and in various other arts and pro- cesses. It is soluble in 1.6 parts of cold, and 0.3 of boiling water. Sulphate of copper or blue vitriol, mineralogically known as chalcanthite, cyanose, and cyanosite, (Gr. kyanos, dark blue), is a fine dark sky-blue salt, having a vitreous lustre, and strong metallic and nauseous taste. It consists of 32 sulphuric acid, 32 oxide of copper, and 36 water, and is found as a product of decomposition in copper-mines, copper-waste heaps, and in 236 SALTS AND SALINE EARTHS. the water issuing from old workings. Though occurring in nature as a secondary production from copper pyrites, or from iron pyrites containing small quantities of copper, it is more frequently prepared artificially, either by the roasting and lixiviation of pyrites and other copper ores, by treating these and metallic copper (old sheathing, copper scraps, and refinery scales,) with sulphuric acid, or as a residuary product of met- allurgic operations. Sulphate of copper when refined is employed in dyeing ope- rations, in calico-printing, as a pigment, in electrotyping, and in various other arts. It is soluble in three parts of cold and in a half part of boiling water. Sulphate of zinc, white vitriol, or Goslarite, as it is mineralo- gically termed, is a salt of a greyish or greenish white, vitreous in lustre, astringent, metallic and nauseous in taste, and occur- ring in old zinc -mines in crystalline tufts, and in massive, botryoidal, and reniform incrustations. It consists of 28 oxide of zinc, 28 sulphuric acid, and 44 water, and is supposed to arise from the decomposition of sulphide of zinc. For indus- trial purposes, " the salt," according to Gmelin, " is prepared by roasting ores containing sulphide of zinc, afterwards ex- hausting them with water, and evaporating the solution to the crystallising point. By fusion in its own water of crystallisa- tion, stirring in wooden troughs with wooden shovels till crystallisation takes place, and subsequent pressing in boxes, commercial zinc vitriol is made to assume the appearance of loaf-sugar." White vitriol is extensively used in medicine and in dyeing. VII. BARYTES STRONTIA. Barytes or Baryta (Gr. barys, heavy) is one of the simple earths, of a whitish or greyish- white colour, deriving its name from its great specific gravity, which is about 4. 2. As deter- mined by Sir Humphry Davy in 1808, it is a protoxide of the metal barium. In nature, it occurs chiefly as a sulphate or carbonate, traversing the older rocks in veins from an inch to several feet in thickness, and familiarly known as heavy spar. ' The native sulphate or "cawk" consists of 65.63 baryta and 34.37 sulphuric acid ; the carbonate, or "Witherite" (after Dr Withering), of 77.59 baryta and 22.41 carbonic acid. These salts of baryta occur abundantly in the British Islands, and are worked in Shropshire, Derbyshire, Northumberland, Cumber- SULPHUR. 237 land, Montgomeryshire, Ayrshire, and till recently in Arran. According to Hunt's 'Mineral Statistics/ the quantity raised in 1872 amounted to 4650 tons sulphate and 4442 carbonate in all, 9092 tons having an estimated value of ^7078. The sulphate is principally obtained from Derbyshire, and from Wetherton and Snailbeach in Shropshire ; the carbonate from Fallowfield near Hexham and Settlingstones in Northumber- land, and from Alston Moor in Cumberland; but available sup- plies occur in Devon, Cornwall, and other parts of the island. The carbonate is employed in the manufacture of plate-glass, as a base for some of the more delicate colours, and in the refining of beet-root sugar; the whiter varieties of the sul- phate, after being heated and thrown into water, are ground, and the heavy white powder used as an adulterant of white- lead. The nitrate is employed in the production of "green- fire " in pyrotechny. Strontia, from the lead-mines of Strontian in Argyleshire, where it was first discovered, is another of the alkaline earths whose metallic base is strontium. It occurs either as a car- bonate (strontianite) or as a sulphate (celestite, so called from its faint tinges of celestial blue). The carbonate is found chiefly at Strontian, the sulphate in the New Red marls of England. Both minerals are found in other countries; but, on the whole, Strontian minerals are rare. As an earth, strontia is nearly as heavy as baryta ; its reduced powder has an acrid burning taste, but not so corrosive as baryta ; its compounds are harmless, while those of baryta are poisonous. The nitrate, which is chemically prepared from the sulphate, is employed in the manufacture of the " red-fire" of the pyrotechnist VIII. SULPHUR. The element sulphur occurs in nature as a greenish-yellow, brittle solid, crystalline in structure, and exhaling a peculiar odour when rubbed. It has a specific gravity of from 1.98 to 2.12; is insoluble in water, but dissolves in other liquids, as oil of turpentine, the fixed oils, and especially in the bisulphuret of carbon. It is a non-conductor of electricity, but acquires negative electricity by friction. It melts at the low temperature of 227, takes fire at 518, and burns with a bluish flame and most suffocating odour. Sulphur occurs abundantly in a free state, chiefly in volcanic districts, where it appears in veins, amorphous masses, in 238 SALTS AND SALINE EARTHS. drusy cavities, or mingled with clay and other earthy impuri- ties Sicily, Lipari Islands, Hungary, Iceland, Jamaica, Mexico, California, East India Islands, and indeed in almost every region of igneous activity. In some districts of Cali- fornia (Omaha) the earthy impurities rarely exceed 15 per cent, in Sicily they often amount to 35 per cent, while in Austria they generally exceed that proportion. Sulphur is also extensively diffused throughout the globe in combination with other substances, forming with the metals the numerous ores known as sulphides, and with the earths the rocks and minerals known as sulphates. It is largely diffused through the waters of the ocean in combination with soda, magnesia, &c., and is present in the structure both of plants and animals. It is ex- tensively employed in the arts, for which it is obtained from volcanic districts in a crude state; from deposits such as those of Poland and Galicia, where it occurs as an ore in connec- tion with clay; or from pyrites, in which it is in chemical union with iron, copper, zinc, or other metal. The preparation of sulphur and sulphuric acid from the metallic sulphides is now an important branch of industrial chemistry; and as these sulphides appear in various conditions and admixtures, the discovery of such as can be used econo- mically, or from which by-products (copper, &c.) can be recov- ered, should be a prime object on the part of the field geolo- gist. The amount of sulphur ore annually brought into the Tyne from Spain, Germany, Norway, and other localities, cannot fall much short of 100,000 tons. Large quantities of sulphur are consumed in the preparation of sulphuric acid, in the manufacture of gunpowder, in the making of matches and fireworks, in sulphuring vines against certain diseases, in vulcanising india-rubber and gutta-percha, in the preparation of certain cements, of ultramarine, and in medicine. It is further employed in the manufacture of sul- phurous acid, sulphites and hyposulphites, sulphide of carbon, vermilion, mosaic gold or bisulphide of tin, and other metallic sulphurets. The substances noticed in the preceding paragraphs are of vast and varied importance in the arts and industries in domestic economy, in medicine, in agriculture, bleaching, dyeing, tanning, glass-making, powder-making, glazing, ena- melling, and numerous other processes. Though seldom found in independent masses of any magnitude, they are widely dif- fused, and require not only geological knowledge to discover their associations, but chemical and mechanical skill to extract SULPHUR. 239 and prepare them for economic application. The majority of them are found as surface deposits in dry and arid regions, but others are intimately blended with the earths, and occur in strata in the older formations. But whether occurring in superficial salinas or as deep-seated beds, whether occurring in native purity or in chemical combination, their presence is readily recognised, and the observant geologist can have no difficulty in bringing them under the notice of the chemist and manufacturer. It is by observation of this kind that the geo- logist best fulfils his function ; and every contribution he can make to the arts and manufactures is at once a triumph of science and a gain to society. Every surface efflorescence, however insignificant, every trickle of styptic water (and every issue of water should be tasted by the field geologist), every mealy disintegration of a rock, and even the presence of such plants as affect saline soils, should all be duly noted as indi- cations of the mineral treasures below. Only a few scattered patches of the earth's crust have been sufficiently explored; the great bulk remains unknown, offering at once the strongest in- centive to scientific research and the most sanguine expecta- tion of industrial extension. Works which may be consulted. Wagner's ' Manual of Technology ' Crooke's Edition ; Knapp's ' Chem- ical Technology ; ' Ure's ' Dictionary of the Arts and Manufactures ' Hunt's Edition; Watt's ' Dictionary of Chemistry.' XV. MINERAL AND THERMAL SPRINGS. CLOSELY related to the Salts and Saline Earths are those mineral and thermal springs whose waters enjoy a reputation for their therapeutic and soothing qualities. These waters are, indeed, but solutions of the salts, or of combinations of the salts already mentioned incorporating, besides, various gases whose liberation on coming to the air gives to many of them their sparkle and piquancy. From the earliest times these waters have attracted the attention of mankind ; their virtues sung, and their sources deified. Issuing from the earth and holding its substances in solution, they come directly under the cognisance of geology, both as regards their chemical compo- sition and the rock-formations from which they flow; and under the notice of the economic geologist for the special medicinal and commercial value attached to theirwaters. To the theoretic geologist they are of special interest, as throwing light on the transformations that are taking place in the interior of the earth, as well as on the nature of the substances so transformed ; and to the industrial geologist they present so many sources of wealth according to the attractiveness of their position and the nature of the ingredients they contain. In Europe and America thousands are annually drawn to them for health and recrea- tion; their waters, in increasing quantities, are bottled and exported to every civilised country ; and in several instances their essential salts are obtained by evaporation, and enter largely into the materia medico, of modern practice. These springs occur in all systems, from the metamorphic schists to the tertiary sands, and from the earliest granitic outbursts to the latest volcanic eruptions being found most abundantly, perhaps, in the older rocks, and in and around former centres of vulcanicity. Wherever there are beds through which water can percolate, or rents and fissures through which it can arise, there it will exert its solvent influences, partly ac- cording to the solubility of the substances with which it comes in contact, partly according to the gases it contains, and partly MINERAL AND THERMAL SPRINGS. 241 according to its temperature hot water, other things being equal, acting with greater energy than cold. In this way various salts of the earths and metals are brought to the surface lime, magnesia, potass, soda, sulphur, silica, iron, c. sometimes singly and simply, and at others numerous- ly and in very complex combinations, sometimes scarcely traceable in the issuing springs, and at others impregnating them almost to saturation. Surface or deep-seated, hot or cold, oozing as the merest trickle, or gushing forth in copious foun- tains, there is no absolutely pure water coming from the rocky crust ; though only that is regarded as " mineral," whose nature manifests itself either to the taste, to the smell, by the bubbling escape of gases, or by its temperature. Looking at springs from a geological point of view, they may be considered under two main heads, Mineral and Ther- mal both holding mineral matter in solution, but the one set characterised by their lower, and the other by their higher temperatures. As already stated, all springs are impregnated less or more with mineral or metallic matters ; but here we notice only those in which the proportions are notable ; and as their temperatures are very varied, we here advert only to those considerably higher than the atmospheric mean of the districts in which they occur. A simple mineral spring may arise either from the solvent power of cold water, as above stated, or it may arise from the solvent energy of hot water at great depths, but which has become cool before reaching the surface ; while thermal springs may arise directly from volcanic heat from that increasing temperature which takes place at the rate of one degree for every 60 or 65 feet of descent into the crust or from chemical interchange, which generally takes place with an evolution of heat more or less perceptible. Springs of all temperatures up to the boiling-point, and some- times beyond it, occur in most volcanic regions, and are evi- dently dependent on the fire-forces that are operating below. The hot springs of Iceland, of the Azores, Tuscany, the Yellow- stone in North America, and New Zealand, are well-known ex- amples on a large scale : but thousands less noticeable are to be met with in all active volcanic centres. Silica, lime, alumina, sulphur, borax, and various metallic salts, are deposited from their waters, while several gases and acid vapours are discharged from them as they come to the surface. The following, from M. de Fouque's account of the hot springs of the Azores (Compt. Rend. Ixxvi.), gives a fair idea of the nature and com- plexity of the waters arising from such centres of vulcanicity : " The valley of Furnas, in the eastern part of San Miguel, was disturbed about three centuries ago by volcanic eruptions, * Q 242 MINERAL AND THERMAL SPRINGS. and the soil is now perforated by a number of geysers. The three largest and most active of these have received the name ' Caldeiras.' One of these only furnishes a continuous stream of water; another sends forth intermittent currents; while the third emits only water, vapour, and gas. Besides these boiling springs, there exist others which possess a temperature about 61 Fahr., and whose waters are ferruginous. The water of some is very alkaline and but slightly sulphurous ; others are not in the least sulphurous : many contain a considerable amount of hydroferric carbonate and carbonic acid ; and some, again, free sulphuric acid. These springs, especially those containing sulphuric acid, are used medicinally. All of them contain a large quantity of silica in solution so large, indeed, that it is deposited at the mouth. Soda salts and free carbonic acid are present in large quantity; while iron, lime, and magnesia are comparatively scarce. Several of the springs contain traces of bromides, iodides, and fluorides ; boracic acid and arsenic are not present." But while thermal springs are most abundant, as might be expected, in volcanic districts, they are also to be found in other regions from which vulcanicity has long since departed, and even in sedimentary areas in which it is difficult to trace any connection with subterranean agencies. The Pyrenees, for example, abound in thermal waters, some exceeding 185, and yet no igneous force has been operating there for ages. The waters of Bath (120) and Buxton (82) issue respectively from oolitic and carboniferous limestones, and are far removed from rocks of eruptive origin. There is little difficulty in assigning a sufficient cause for thermal waters when they occur in volcanic centres ; but when issuing from old hill-ranges, or from sedi- mentary rocks, the difficulty is greatly increased, and we must fall back upon residual connections with old igneous foci, upon the gradually increasing temperature which is experienced as we descend into the crust, or upon chemical changes which are still going on among the deeper-seated strata. The problem is beset with many difficulties ; and in the mean time geology must rest contented with indicating rather than with assigning a true and sufficient cause. In another Chapter (VII.) reference has already been made to the stratigraphical relations of springs and subterranean waters, but here it may be recapitulated, that they occur most frequently along lines of faults and fissures ; that they appear in greatest numbers in broken and dislocated areas ; that they break out at all heights, but most abundantly along the flanks of mountains and in abrupt valleys ; that they are found most copiously at depths not exceeding 2500 feet; and that in well- MINERAL AND THERMAL SPRINGS. 243 defined basins they generally partake of the same mineral character. It must be remembered, however, that water-bear- ing beds containing different mineral constituents may occur at different depths in the same formation ; and as a consequence chalybeate and sulphur, saline and earthy, and even cold and hot, may break forth within a few hundred yards of each other. In this way springs of varied character often appear in clusters as, for example, at Homburg and our own Harrogate. Springs, as already stated, arise from every formation ; but those most abundantly charged with mineral salts are more frequent in sedimentary than in igneous rocks. In igneous masses, whether granite, greenstone, or lava, the mineral is more crystalline and compact, and less pervious to water; in sedimentary strata the particles are less crystalline and co- herent, and therefore more pervious and accessible to the solvent power of the permeating fluid. Springs issuing from granites and greenstones are comparatively pure ; those arising from sands, gravels, sandstones, limestones, shales, and iron- stones, are all more or less impregnated with mineral and metallic matter. The soluble matters occurring in stratified formations, whether tertiary, secondary, or primary, are very numerous ; hence the complex composition carbonates, sulphates and chlorides of lime, magnesia, potass, soda, and iron, as well as silicic acid of many of our mineral waters. No doubt, water issuing from limestones will be chiefly cal- careous, from ironstones chalybeate, from rock-salt saline, and from volcanic tracts, if hot, chiefly silicious ; but generally speaking, subterranean waters traverse many different beds, and during their percolation new combinations are brought about which render their ultimate composition very complex, and very difficult to be accounted for. There is, perhaps, no branch of chemistry so difficult as that of water-analysis ; no problem in geology so perplexing as that relating to the origin of the salts and gases held in solution by mineral waters. The following substances, some of them in very minute proportions, have been detected by spectrum analysis in the waters of Germany : Oxygen and ozone, nitrogen, chlorine, hydrogen, carburetted hydrogen, carbonic acid, ammonia ; hydrosulphuric, hydrochloric, sulphuric, sulphur- ous, nitric, nitrous, phosphoric, antimonic, silicic, and boracic acids ; calcium, sodium, potassium, bromine, iodine, fluorine, arsenic, sulphur, lithium, rubidium, caesium, barium, strontium, magnesium, aluminium, manganese, iron, copper, lead, and zinc. The really important constituents, however, according to Dr MacPherson (' Baths and Wells of Europe ') are carbonate and sulphate of soda, chloride of sodium, carbonate and 244 MINERAL AND THERMAL SPRINGS. sulphate of magnesia, carbonate and sulphate of lime, car- bonate and sulphate of iron, sulphurets of sodium and of lime, bromine and iodine, carbonic acid and nitrogen. As these ingredients are evidently the result of decompositions and transformations taking place in the interior of the earth, one would naturally suppose that in course of time mineral springs would become feebler in composition and cooler in tempera- ture and so in course of ages they must. It is remarkable, however, that many celebrated by the ancients are still in equal favour, and, as far as observation has been recorded, flow as freely as ever, maintain the same temperatures, and discharge the same amount of saline constituents. Owing to the variety and complexity of their substances, it is very difficult, in treating of mineral waters, to classify them in any simple and intelligible manner. To speak of them merely as calcareous, silicious, saline, and chalybeate, is too general ; and to attempt any strictly chemical classification is, in the mean time, impossible. The following, according to the authority above quoted, is a popular French arrangement : i. Sulphur waters, f Sulphuret of soda. ( Sulphuret of lime. f Chloride of sodium. 2. Common salt waters, . < Chloride of soda, bicarbonated. ( Chloride of soda, sulphuretted. f Carbonate of soda. 3. Bicarbonated waters, . < Carbonate of lime. ( Mixed carbonates. f Sulphate of soda. 4. Sulphated waters, . ) Sulphate of magnesia. ' I Sulphate of lime. V Mixed sulphates. . f Bicarbonate of iron. 5. Iron waters, ' ( Sulphate of iron, with manganese. And the following is that usually adopted in Germany : i. Alkaline, '*' '.' ; v {a. Simple carbonated. 6. Alkaline. c. Alkali and common salt. 2. Glauber-salt, {a. Pure. 3. Iron, .. ' ; ----- -. b. Alkaline and saline. c. Earthy and saline. {a. Simple. 4. Common salt, . - . :.--..- b. Concentrated. c. With bromine or iodine. 5. Epsom salt. 6. Sulphur. 7. Earthy and calcareous. 8. Indifferent. After all, as the principal interest of mineral springs arises from their reputed medicinal virtues, that arrangement usually adopted by the Faculty, if not the most scientific, is perhaps the most appropriate ; namely, Indifferent, Earthy, Sulphur, Saline, MINERAL AND THERMAL SPRINGS. 245 Alkaline, Purgative, and Chalybeate. To these may be added the Bituminous, which, though chiefly valued for their illumi- nating products (Chap. IX.), have long been employed as lu- bricants and plasters in certain external affections. Under these respective heads we may glance at some of the more celebrated, and in particular at those of our own islands. Indifferent Waters. Under this head are usually ranked such waters as contain a very small amount of mineral constituents ranging, for in- stance, from 2 to 6 parts in the 10,000. So feeble, indeed, are many of them that they would have escaped notice, and been regarded as simple potable waters, had it not been for their temperature, which varies in the better known of Europe from 63 to 140 Fahr. Among the most notable of these waters are Gastein (3.4, 95-u8), Pfeffers (2.9, 99.5), Wilbad (5.7, 95-ioi), and Teplitz (6.7, ioi-i2o), in Germany; Plombieres (2.8, 66-i58), Bains (3, 73-i2o), and Chaude- fontaine (3, 94), in France; Caldas de Oviedo (1.5, 108) and Panticoza (1.9, 85-95) in Spain; and Buxton (3.2, 82) and Matlock (68) in our own country. The springs of Bux- ton and Matlock rise from the thick-bedded mountain lime- stone of Derbyshire the former containing, according to Dr Lyon Playfair, about 20 grains of saline ingredients per im- perial gallon; namely, carbonate of lime 7^, carbonate of magnesia 4^, sulphate of lime, the chlorides of sodium and potassium, 2^ each: with fractional proportions of silex and iron oxide. Besides the solid contents, there are discharged, at the moment the water issues from its source, about 3.47 cubic inches of carbonic acid, and 206 cubic inches of nitro- gen per gallon. Various theories have been advanced to account for the temperature and constituents of the Buxton waters ; but none of them, in the mean time, have been re- ceived as satisfactory. Chemical changes are, no doubt, going on below, and something must be suffering oxidation ; but what or where ? is the problem that still awaits the solution of the chemical geologist. Several of these indifferent springs are largely frequented during their respective seasons their waters being used both for drinking and bathing. Their therapeutic virtues are vari- ously extolled dyspepsia, rheumatism, affections of the joints, gout, neuralgia, loss of power, and paralysis, being among the maladies on which they are said to have a beneficial effect. As the majority of them are situated in elevated and picturesque regions, perhaps the bracing air, change of scenery, and cheerful society, may not be the least of their hygienic recommendations. 246 MINERAL AND THERMAL SPRINGS. Earthy Waters. Earthy waters are those which hold in solution a consider- able portion of the salts of lime, magnesia, alumina, and other earths. They differ from the indifferent springs chiefly in the larger amount of mineral ingredients, as well as in the higher temperature which seems necessary to dissolve and sustain these increased proportions. Their most abundant salts are carbonate and sulphate of lime, carbonate and chloride of magnesium, sulphate of soda and chloride of sodium, sulphate of potass, and sulphate of alumina. Their solid constituents vary from 10 to 44 parts in the 10,000; and their temperature from 80 to 1 60 and upwards. Among the most celebrated of these earthy waters are Lucca (26.3, 122), San Giuliano (34.5, 105), and Bormio (10.3, 104), in Italy; Bagneres de Bigorres (28.4, 123), Garsao (4i-48), St Amond and Con- trexeville, in France; Leuk (18.6, 123) and Baden (53.4, 124) in Switzerland; Sacedon (85), Alzola (87), and Fitero (118), in Spain; and Bath (20.2, io8-i2o) in our own coun- try. The springs of Bath rise from the oolitic limestones of the district, and have, according to the analysis of Meek and Galloway, the following composition, viz. : Carbonate oflime, 8. 820 grains. Carbonate of magnesia, . . . o. 329 Carbonate of iron, . . ... . 1.873 Sulphate of lime, . 80.052 Sulphate of potass, . . . . . . 4.641 Sulphate of soda, . . . V . ''. . 19.229 Chloride of sodium, . . ..;". . 12.642 Chloride of magnesia, . . . , . . 14.581 Silicic acid, . . . 2.982 An imperial gallon containing 144.018 grains. Therapeutical ly, these earthy waters are used much more for bathing than for drinking, though some of the weaker sorts are taken internally in limited quantities. Several of them have a high reputation for rheumatism, partial anchylosis of the joints, neuralgia, partial paralysis, uterine, nervous, and cutaneous affections ; and are not only annually visited by thousands, but are bottled (Contrexeville, Pougas, &c.,) and exported in con- siderable quantities. Several of them have been known and used from the time of the Romans, and no doubt by the primitive .inhabitants, in their own rude way, long before Rome and the Romans had existence. Sulphur Waters. Several of the waters noticed under the heads Indifferent and Earthy contain traces of sulphur; but only those emitting sulphurous odours or depositing sulphur from their stream are MINERAL AND THERMAL SPRINGS. 247 entitled to be ranked under the present section. They are weak solutions of sulphur in combination with alkalies, or of hydrosulphuric acid, and in all likelihood arise from the de- composition of sulphides in the rocky interior. They may be cold or hot and the majority are undoubtedly thermal; but those occurring in the British Islands are exclusively cold. Their mineral constituents are very varied, ranging from 3 to 156 parts in 10,000, and of this the sulphur may vary from the merest trace to 4 ; while their temperatures range from cold and lukewarm up to 185. Among the most celebrated of these are Bareges,* Cauterets, St Sauveur, Eaux- Bonnes, Eaux-Chaudes, Bagneres de Luchon, and Ame'lie de Bains, in the Pyrenees ; St Honore, Enghien, Pierrefonds, Challes, and Aix-le-Bains, in France ; Santander, Archena, Carballo, and Caratraca, in Spain ; Baden, Schinznach, Stachelberg, Gurni- gel, and others, in Switzerland ; Baden, Ofen, and Mehadia, in Austria; Aix-la-Chapelle and Weilbach in Germany; Acqui and Abano in Italy ; Harrogate, Askern, Dinsdale, Gilsland, and Shap, in England ; Llandridnod in Wales ; Moffat and Strathpeffer in Scotland ; and Lisdunvarna in Ireland. The following tabulation, from Dr MacPherson's * Baths and Wells of Europe/ will give some idea of their composition and char- acter : Cold Sulphur. Sulphur. Total contents. Tempera- ture. Eleva- tion. Cambo, .012 .015 .071 .150 .326 435 .896 2. 2OO m Sulphu trace 039 .048 .095 .096 .097 135 :$ .230 .229 .870 32.4 19.3 n.6 141. 27.6 30-7 156. 8.4 r. 28.8 21. 3- I 7 2.5 1.8 65-9 2.1 y 26.2 108.5 140. 96.8 147. 90.5 109. 134- 185. "3- 135-5 167. 96.7 3600 1425 300 765 520 2100 8 10 2400 2525 3254 4100 2000 1060 Weilbach Neundorf, .... Enghien, .... Harrogate, .... Challes, War Aix-les-Bains, Aix-la-Chapelle, Eaux-Chaudes, Eaux-Bonnes, S. Sauveur, .... Cauterets Bareges, .... Luchon, .... Schinznach, .... * The glairy semi-organic substance, known as Baregine, was first detected in these waters, but has since been found in several of the hot Pyrennean springs. Its nature and origin are still imperfectly understood. 248 MINERAL AND THERMAL SPRINGS. The sulphur wells of Britain (Harrogate, Askern, Dinsdale, Gilsland, Snap, Moffat, Strathpeffer, Llandridnod, and Lis- dunvarna) are much frequented by invalids and pleasure- seekers, who have the advantage not only of the sulphur waters, but of the saline and chalybeate springs which occur in the neighbourhood. Sulphur, sulphate and carbonate of lime, chloride of sodium and sulphate of soda, carbonic acid, and sulphuretted hydrogen, are their chief constituents, though in general they have a very complex composition, as may be seen from Professor Hoffman's analyses of three of the Harro- gate springs : Old Well. Montpellier W. Hospital W. Sulphate of lime, .182 594 51.660 Carbonate of lime, . Chloride of calcium, 12.365 Si-735 24. 182 61.910 25.560 Chloride of magnesium, Carbonate of magnesia, SS-693 54.667 17.140 3- 2 5i Chloride of potassium, 64.701 5-750 3-975 Carbonate of potasa, Chloride of sodium, 866.180 803.093 369.014 Sulphide of sodium, 15-479 14.414 7-155 Carbonate of soda, . Silica, .246 1.840 525 Total grains per gallon, 1096.580 966.456 437.968 With traces of bromide and iodide of sodium, ammonia, carbonates of iron and manganese, and organic matter. The gases evolved are carbonic, car- buretted hydrogen, sulphuretted hydrogen, and nitrogen ranging from 20 to 40 cubic inches per gallon. Employed both internally and externally, these sulphur or saline-sulphur waters have a high reputation both at home and on the Continent, are annually visited by thousands, and in some instances (Challes, near Chambery, &c.) bottled and ex- ported. In local guide-books and medical works on mineral waters, their curative properties embrace a wide range of maladies rheumatism, affections of the bones and joints, neuralgia, dyspepsia, hypochondriasis, chronic constipation, cutaneous disorders, scrofula and glandular enlargement, abdominal plethora, local congestions, and mucous catarrhs, being chiefly dwelt upon as yielding to their medicinal virtues. On the Continent many of these springs are situated in pretty and picturesque or in high and bracing situations, and afford ample opportunities for pleasant relaxation, often as beneficial MINERAL AND THERMAL SPRINGS. 249 as medicine; but at home, with the exception, perhaps, of Dinsdale, Gilsland, Moffat, and Strathpeffer, our saline-sulphur springs are situated in localities which have anything but genial or attractive surroundings. Saline Waters. In those waters usually designated Salt or Saline, common salt or chloride of sodium is the characteristic ingredient, and this is most frequently associated with chloride of calcium, carbo- nate of lime, and chloride of magnesium. A great many springs contain salt in small proportions ; but only those in which it is distinctly perceptible to the taste are entitled to the designa- tion of saline. They arise from all formations, from the Silurian to the Tertiary inclusive ; but in England brine-springs proper are restricted to the Trias. Many of these are, no doubt, con- nected with deposits of rock-salt ; but others, and perhaps the majority, derive their salinity from slow solution and chemical transformation. In some instances it has been attempted to trace them to infiltrations of sea-water ; but, generally speaking, this is an untenable hypothesis, as they occur in Silurian, Old Red, and Carboniferous districts hundreds of miles from the sea and hundreds of feet above its level. They are found in every region of the globe, and have early attracted the attention of mankind, as well as of many of the lower animals that periodi- cally frequent their sources either to drink or bathe in their waters, or to lick the saline muds that surround them. Thera- peutically, some of the weaker sorts, and in which there are other salts, are used chiefly for drinking ; others, which are also of mixed composition and thermal, are used both for drinking and bathing ; while the more concentrated, whether hot or cold, are employed mainly for bathing. Closely connected with these springs are the salt-lakes which occur in various parts of the world Africa, Central Asia, and North America and which are fed either directly by salt- springs, or by streams that traverse tracts of saline sands and gravel. These lakes vary in size from mere pools to seas like Aral, thousands of square miles in area, and in salinity (according to the season of the year) from waters slightly brackish like those of the Caspian, to others intensely bitter like those of the Dead Sea, which contain fully 24 per cent of mineral ingredients. The follow- ing tabulation exhibits the character of some of the better known and more frequented salt-springs in Europe : 250 MINERAL AND THERMAL SPRINGS. Cold Salt- Springs. Salt. Mineral contents. Temp. Car. acid. Kronthal, .... 29. 38.3 36. Niederbronn, . . . 30.8 46.2 Kissingen, .... 61. 85.2 3L9 Kreusnach, .... 95-5 112. 2 IO2. 132.9 26. q Soden . . 14.8 Q 166.1 .. 16 7 Woodhall j-^u.y 214. 279. J.U./ German Ocean,* . . 285.8 371- Thermal Salt-Springs. 6.2 Q. XM Luxeuil 7 7 V ii. 6 Ai o TOQ Canstadt / / 2O. 4.t. c X ^J ye 18.2 Baden-Baden, 23.1 TOO 27.2 /o r 5S Bourbonne, . 57-7 74-7 149 ... Wiesbaden, . La Porretta, 69.8 83.4 82. 90. 156 95 10.3 Nauheim, 165.4 2 3S- 103 16.9 Monte Catini, 180.8 221.3 88 ... * The following is the mean of several analyses of SEA- WATER by M. Reg- nault : Water t Chloride of sodium, . Chloride of magnesium, Chloride of potassium, Sulphate of lime, Sulphate of magnesia, Carbonate of lime, Bromide of magnesium, Loss (including iodides, silica, &c.), .... Saline Ingredients, 3-505, 66.470 2.700 0.360 0.070 0.140 0.230 0.003 O.OO2 0.25 100.000 Besides common salt, most of these waters contain salts of lime, magnesia, soda, iron, iodine, and other ingredients. Many of the Continental springs (Kissingen, Homburg, Soden, Wies- baden, Baden-Baden, Ischia, Monte Catini, &c.) have a high reputation and are much frequented; while their waters are bottled, and in some instances largely exported. In our own country we have such saline waters as those of Droitwich, Gloucester, Ashby de la Zouch, and Woodhall, in England ; and Bridge of Allan, Pitcaithly, and Innerleithen, in Scotland some of which are fairly frequented, partly for their waters and partly for their sheltered situations (Bridge of Allan and Gloucester) ; while the water of others (Woodhall), containing bromides and iodides, is further exported for drinking. The MINERAL AND THERMAL SPRINGS. 251 following is an analysis of the Woodhall waters as given in Dr Lee's ' Watering-Places of England : ' Common salt, . 189^ grains per pint. Muriate of lime, Muriate of magnesia, Iodine, . Bromine, Nitrogen, cubic inches. Carbonic acid, . These saline waters, hot and cold, are administered inter- nally and externally for a long list of diseases scrofula, cuta- neous affections, anaemia, dyspepsia, relaxed habit and general debility, various nervous affections, rheumatism, gout, and dis- orders often arising from intemperate and reckless living. How far they may be efficacious, or on what speciality their efficacy may depend, lies beyond our sphere ; but viewed from an econ- omic or industrial point, they are the means of annually circu- lating millions of money, and bringing wealth and activity to districts that would otherwise remain poor and unfrequented. We have said nothing of the sea, which is the great centre and reservoir of all saline waters, nor of sea-bathing, which is of universal application as a bracer, healer, and restorer. The favourite resorts along our own shores are very numerous ; and while it may be said that the eastern coasts are more bracing and the western more sheltered, and that some beaches are cleaner and safer than others, still it is simply fashion and caprice which make one place thronged and popular for a few seasons, and leave another, equally eligible for its waters, dull and deserted. Alkaline Waters. As might be expected, from their abundance and frequent combinations in the rock-masses of the crust, the alkaline earths are held largely in solution by the percolating and issuing waters. There is scarcely a spring that comes to the surface which does not contain one or other of their salts carbonates, sulphates, phosphates, sulphides, and chlorides, and this from formations of all ages, sedimentary and eruptive. These waters in which lime and magnesia prevail, have already been noticed under the head of Earthy ; those in which soda and potass are the effective ingredients are regarded as the Alkaline proper. Lithia and strontia are occasionally present, but generally in very minute proportions, though great stress is laid by some practitioners even on the merest traces of these, and such substances as iodine, bromine, fluorine, and arsenic. France and Germany are rich in alkaline waters, 252 MINERAL AND THERMAL SPRINGS. cold and hot ; Britain has none of importance. These Con- tinental springs are not only frequented by thousands for drinking and bathing, but are bottled (Vichy, Seltzer, Heil- brunnen, Bilin, &c.) in very large quantities and exported to other countries. The following tabulation exhibits the chief or effective constituents of some of these celebrated waters omitting, of course, the other ingredients (lime, potass, &c.) which are generally present in greater or less abundance : Carb. of soda. Carb. of magn. Common salt. Carbonic acid. Temp. Vichy, 37-7 5-0 5-0 26.0 105 Bilin, 30.0 5-4 3-8 26.0 Gleichenberg, 25.1 7.8 19-5 27.0 ... St Nectaire, . 24.6 6-7 26.9 24.0 in La Bourboule, 19.4 2.8 39-6 23.0 I2 5 Vic sur Pere, . 18.6 6.0 .12.3 21. Heilbrunnen, 18.2 10.7 14.1 36.8 Salzbrunn, 17.4 6-3 i-7 46.0 Chateauneuf, 16.20 4-3 3-i 36.0 100 Ems, J 3-9 2.8 IO. I 18.9 "5 Royat, 13-4 6-7 17.2 6.0 95 Sellers, . . 8.0 4.6 22.7 20.3 Neuenhar, 7.8 4.4 0.9 18.8 92 Mont Dore, . 6-3 0.9 3-8 114 Wildungen, . 5-9 8.6 10.5 29-3 Nens, . . . 4.1 1.8 I -7 125 Some of these waters are used chiefly for drinking, some chiefly for bathing, and others indiscriminately for drinking and bath- ing. When taken internally, they are said to be efficacious in cases of dyspepsia, liver complaint, diabetes, gravel, gout, and bronchial affections ; when used externally, or both internally and externally, they are recommended not only for the preced- ing cases, but for rheumatism, enlargement of the joints, neu- ralgia, hysteria, and certain female diseases. Their reputation as tonics, diluents, and dissolvents, has led to their artificial manufacture, and a very large trade is now carried on, especi- ally in Britain, in the production not only of alkaline, but of earthy, saline, and other mineral waters. Given, for example, the composition of a Vichy water, as Carbonate of soda, . ,, potash, , , magnesia, ,, lime, Sulphate of soda, Chloride of soda, Carbonic acid gas, . 37-7 2.7 5-0 3-i 2.9 26.0 with minute quantities of phosphate of soda, arsenate of soda, and carbonates of strontian and iron there is no great diffi- culty in chemically imitating the original. Indeed some pre- MINERAL AND THERMAL SPRINGS. 253 fer the artificial to the natural, as being less vapid, and more sparkling and palatable ; but where the latter has been freshly obtained, and properly secured, the Faculty give it, of course, the preference. Purgative Waters. Under the head of Purgative Waters are usually arranged such as contain sulphate of magnesia and sulphate of soda in notable proportions ; those in which the former salt is pre- sent being regarded as the stronger ; and those from which it is absent the weaker varieties. Germany is the great headquarters of purgative waters ; France, Italy, and Spain contain com- paratively few; and in England they are represented by such springs as those of Cheltenham, Leamington, Scarborough, Epsom, Beulah, Streatham, and Trowbridge. Many of these springs arise from Secondary formations : some are cold, others hot ; some are used solely for drinking ; some for drinking and bathing ; several of them are extensively bottled and exported (Piillna, Friederichshall) ; a few (Seidlitz, Epsom, &c.) imitated and artificially prepared ; and some (Cheltenham) evaporated and manufactured into salts. Generally speaking, they have a fair reputation, and some of them (Karlsbad, Marienbad, Elster, &c.) are annually frequented by visitors from all parts of Europe. The following tabulations are given by Dr Mac- Pherson, as exhibiting, in a general way, their characteristic ingredients : Stronger Purging. Solids. Sulph. magn. Sulph. soda. Com. salt. Carb. acid. Ofen, 35048 160.1 I 5- 2 Ptillna, . 322.8 121. 167.1 5-2 Friederichshall Saidochiitz, . , Kissingen, ' ''-. " 252.4 233-3 230.7 51-4 109.9 57-4 62.5 66.1 60.5 118.7 79-4 6.9 4-5 Uriage, . 141.1 25-6 22.9 72.3 ... Beulah, . Cheltenham, 129.3 117. 92. 18.2 23.2 22.2 3-2 Weaker Purging. Solids. Carb. soda. Sulph. soda. Com. salt. Carb. acid. Tern . Karlsbad, . 54-2 13-6 25.2 "3 7.6 164 Marienbad, 95-4 12.9 o 20. 29.6 Elster, 57-5 29.4 18.6 21.7 Tarasp, 121. 6 35-5 25-4 38.3 45-4 Best rich, IT'S 1.8 9-2 4.9 3-3 90 Fured, 22.7 I.O 9-5 9 30-5 St Gervais, Si-6 1.2 28.2 17.9 126 Leamington, 134-9 52.7 52.3 254 MINERAL AND THERMAL SPRINGS. While the purgative waters of Germany are much esteemed and largely frequented, those of England seem to have fallen into disrepute, or at all events are not now sought after as they used to be. Epsom and Beulah are rarely heard of; Chelten- ham, formerly crowded by thousands, has fallen into compara- tive neglect ; Trowbridge is much in the same condition ; Streatham has still its local visitors ; Leamington continues to be a favourite resort for certain health-seekers; and Scarborough is much more sought after for its sea-baths, and as a place of fashionable relaxation, than for its mineral waters. Various causes may have contributed to this : the handier use of saline laxatives at home ; greater facilities of visiting the stronger German waters ; and last, but not least, perhaps, the mere caprice of fashion, which unaccountably removes its favours from such places as Bath and Cheltenham, and as unaccount- ably transfers them to others, as Brighton and Scarborough. The composition of the Beulah, Cheltenham, and Leamington waters has been already indicated ; the following is that of the South Well at Scarborough in grains per gallon : Chloride of sodium, . 39.63 grains. Sulph. of magnesia, Sulph. of lime, Protox. of iron, Nitrogen, . 225.00 ,, 48.21 1.48 6.3 cubic inches. Among the diseases said to be removed or alleviated by the use, external and internal, of these purgative waters, are enu- merated dyspepsia, habitual constipation, affections of the liver, internal congestions, urinary complications, and general obesity. Many of them, from the amount of carbonic acid they contain, are pleasant to drink ; some are agreeably saline, and not a few are slightly acidulous. Chalybeate Waters. Chalybeate or iron springs have long been celebrated for their tonic qualities, and indeed few natural waters are palatable without a small percentage of the carbonate of that metal. They occur abundantly in all formations, from the metamor- phic schists to the tertiary inclusive, and are easily detected by the ochrey tinge that marks the sides of their channels, the rusty iridescent scum which frequently floats on their surface, and their pleasant astringent taste. Wherever there is iron in the crust, whether in veins, in beds, or in minute dissemination through any stratum, there the per- meating waters will act upon it, and in their upward course bring more or less to the surface. In this way, and as iron is by far the most abundant metal, there is scarcely a district without chalybeate springs, although it is only those in which MINERAL AND THERMAL SPRINGS. 255 the proportions are considerable that are sought after for medi- cinal purposes. And yet several of those which have a reputa- tion are not one whit stronger than (if indeed so strong as) dozens we have met with among the metamorphic rocks, the Silurian, the old Red, and the Carboniferous formations of our own island. The following is given in the * Baths and Wells of Europe,' as exhibiting the nature of some of the better known chalybeates : Mineral constituents. Carbonate of iron. Carbonic acid. Tunbridge, . i-3 .6 2. Wildungen, 3-i 35 24.8 Schwalbach, 4-3 .6 53-5 Spa, . 5-7 .5 17- Neuhain, Soden, 8. .48 40. Malmedy, 12.6 .48 25-5 Wyh, . 12.8 2 5 41. Liebenstein, J 3-9 56 2 3- St Moritz, 14.4 .24 30.2 Elster, 20.9 .62 25- Marienbad, 21.5 .42 12. Pyrmont, 23-4 56 2 7 .6 Griesbach, 26.4 .56 29.4 Tarasp, 36.5 33 37-2 Homburg, 40. 47 41. Among these chalybeate springs, Schwalbach, Spa, St Moritz, Wildungen, and Liebenstein have a high reputation, and are much frequented ; while the waters of others are not only drunk on the spot, but bottled and exported. Britain, though containing numerous common chalybeates, is not rich in those impregnated with carbonic acid ; hence their minor reputation as compared with those of the Continent. Tun- bridge is still frequented ; and the chalybeates of Buxton, Har- rogate, Gilsland, &c., are taken by those seeking the other waters of these places ; but there are dozens of springs scattered through the country, and in some instances thera- peutically taken by the local inhabitants. Among these we may notice the Melrose spring, which is favourably spoken of, and next to " Muspratt's Chalybeate " at Harrogate, re- garded as the richest chalybeate in Britain. According to Professor Dewar it contains 78.1 grains of solid ingredients per gallon, namely Carbonate of iron, . 17.5 grains per gallon. Silica 8.5 ,, Sulphate of magnesia, . Chloride of calcium, . Carbonate of lime, Alkaline chlorides, . 7-8 16.0 ,, . 11.4 ," 256 MINERAL AND THERMAL SPRINGS. The stronger iron-waters, or those containing sulphate of iron (Sandrock, Isle of Wight, Hartfell near Moffat, Vicars Bridge near Dollar, &c.), are generally impregnated with lime and alum, and are too unpalatable to be taken internally. The Dollar water is not unfrequently applied externally as a powerful astringent. Chalybeates are chiefly esteemed for their tonic qualities dyspepsia, anaemia, internal haemorrhages, chlorosis, general debility and relaxation, nervous affections, as hysteria ,and neuralgia, being among the complaints on which they are reputed to exert their beneficial influences. Bituminous Springs. Wells yielding petroleum or rock-oil have long been valued for their therapeutic virtues. They rise from many formations (see Chap. IX.), and seem to be the result of a slow natural distillation of bituminous shales, coals, and lignites. Chiefly of vegetable origin, and in some instances partly of animal, the bitumen usually issues forth with water, on which it floats as a dark-brown scum, having a soft oily feel, and rich em- pyreumatic odour. Petroleum occurs in many parts of Asia, and was there early used as an unguent for sores and cutane- ous affections. It is found most abundantly in North America, and there applied (Seneca oil) as a lubricant, a healer of old sores, and an ointment in skin affections by the Red Indians. In Europe, though now almost out of use, .it is still occasionally employed the old oil-well of St Catherine near Edinburgh, for example, being yet in reputation, and its petroleum skimmed off and applied as a medicament in various skin diseases, and in glandular and rheumatic affections. From early notices of this "sacred well" its oil seems to have been similarly em- ployed by the populace of the district during the last four or five hundred years. The oils of our shale-works, though at first producing a slight cutaneous eruption, are said to have subsequently a beneficial influence on the health of those engaged in their manufacture. Mud-Springs. In many volcanic regions, as well as in other districts from which vulcanism has long since departed, there occur mud- springs of various composition and temperature -fumaroks, self at ar as, hornitos, salses, &c. Some of these discharge hot sulphurous muds and vapours ; some hot water, steam, and mud ; some acidulous waters and mud ; and others, steam, gases, and mud of complex composition and varied consistency. MINERAL AND THERMAL SPRINGS. 257 Owing partly to their temperature, and partly to their mineral constituents, several of them have acquired therapeutic repu- tations as baths, and are visited by invalids suffering from rheumatism, affections of the joints, partial paralysis, and analogous diseases, and not unfrequently with beneficial results. St Amand in the Pyrenees, and Abano, Acqui, and Valdieri, in Italy, may be taken as examples of such mud- baths ; the peat-baths and sand-baths of Germany are artificial preparations. Analyses of these discharges from the Azores, the Yellowstone, Andes, New Zealand, &c., show great variety of ingredients, not only of a mineral and metallic, but also of an organic nature, and for whose presence it is extremely difficult to account. Silica, alumina, and sulphur, with salts of lime, soda, and magnesia, are generally the predominating constituents. From what has been stated in the preceding pages, it will be seen that mineral and thermal springs have not only a scientific interest, but a direct commercial or industrial value. Apart altogether from their therapeutic importance to those benefited by their waters, and which cannot be estimated in a pecuniary way, their economic aspects present themselves in a three-fold form. First, many of them are annually visited by thousands, thus bringing population and wealth to the districts in which they are situated ; second, the waters of several are bottled and exported in large and increasing quantities ; * and third, the efficacious salts of others are recovered by evapora- tion, and become part of the stock-in-trade of the chemist and druggist. Viewing them in either way, they are as important to the economic geologist as the rocks, minerals, and metals of the solid crust ; and it should be his endeavour to observe and bring under notice such springs as contain any marked amount of mineral ingredients, or from whose waters there may be any sensible escape of gases. Such springs may be struck in field-draining, in quarrying, in railway cuttings, or in borings for coal ; and the intelligent observer should ever be on the outlook for their occurrence. The experienced field-geologist does not require to carry a laboratory with him to detect such waters. There is always enough in the taste, in the odour, the bubbling up, or in the temperature, to indicate, in a general, way, the character of a spring ; and it is such indications that * We have no statistics of these exports ; but judging from the general use in Britain of such waters as those of Vichy, Seltzer, Carlsbad, Piillna, Friederick- shall, Marienbad, Kissingen, Schwalbach, Ems, Vails, Saratoga, Carrara, &c., the amount must be very considerable. R 258 MINERAL AND THERMAL SPRINGS. should lead him to the chemist, and from the chemist to the medical practitioner. The discovery of a mineral spring may be, as the com- mercial phrase goes, "the making of a place." Many of the watering-places of France and Germany have risen during the current century from obscure hamlets to populous and fashion- able towns ; and at home, Bath, Buxton, Cheltenham, Harro- gate, Moffat, and similar places, have been the direct creation of their thermal and mineral springs. The beauty and amenity of a place may occasionally have much to do with its popu- larity; but no such adjuncts have contributed to the rise of Harrogate, Buxton, or Moffat. But for its springs, there is no special claim in the landscape of Harrogate ; and but for its spa, no one would ever think of spending the summer months among the monotonous solitudes of Shap. What ironstone is to Cleveland, coal to Newcastle, and granite to Aberdeen, so are these mineral and thermal springs to the districts in which they are situated sources of wealth and promoters of general industry. The discovery of a mineral spring may be as im- portant to a locality as the discovery of a seam of coal, with this essential difference, that while the coal may be worked out in a few years, the waters of the spring will continue to flow unchanged for centuries; and that while the coal requires expensive and dangerous labour to bring it to bank, the mineral waters gush forth into the open day in readiness to be used and utilised. Enough, we think, has been said to show the importance of the mineral and thermal waters that issue from the rocky crust. Therapeutically, it is extremely difficult to account for the action of several ingredients they contain, and especially of those which, like iodine, bromine, lithium, and arsenic, occur in such infinitesimal quantities. Still, there is the fact of these waters being taken and believed in ; and however much doctors may differ as to their special properties and effects, many of them have been frequented from time imme- morial, and still continue to be frequented by increasing numbers as nations get wealthier and more luxurious, and as facilities for travelling become more general and extended. Works which may be consulted. Macpherson's ' Baths and Wells of Europe ;' Macpherson's 'Our Baths and Wells, or the Mineral Waters of the British Islands;' Lee's * Watering- Places of England ; ' Lee's ' Baths of Germany ; ' Watt's ' Dictionary of Chemistry.' XVI. MINERAL MEDICINES. THE mineral preparations used in medicine, though small in amount compared with those employed in the ordinary arts, are still, commercially speaking, of considerable value. It is not so much the bulk of the materials, as the skill and care be- stowed on their purification and duly-proportioned admixtures, that add to their pecuniary importance. As these prepara- tions are all derived from the earths and metals described under other sections, it would be superfluous in the present chapter to do more than merely allude to the names and rela- tive amounts of the natural substances. It would be still further out of place, in a work on Economic Geology, to enter upon their therapeutic virtues, and all the more that medical practitioners are often at variance both as to reputed efficacy, bulk of dose, and mode of administration. All that is here needed is a mere enumeration of the mineral materia medica, that the student may perceive how intimately every product of the earth is connected with man's wellbeing and comfort, and consequently becomes a marketable or commercial com- modity. Nor is it alone the raw materials and their pharma- ceutical preparations, but the medical skill in testing their efficacy, and the chemist's care in dispensing, that must be taken into account in estimating the material importance of the mineral medicines. A large amount of highly-skilled la- bour is expended upon them at every stage of their prepara- tion; hence their mere bulk bears no proportion to their veritable value. Arranging these substances alphabetically, as in works on Materia Medica and Therapeutics, we have the following summary : Alum, in solutions and in powder as dried or burnt alum used internally as an astringent and purgative ; and externally as an astringent and escharotic. Ammonia, as free ammonia, and in several preparations as th 260 MINERAL MEDICINES. carbonate, bicarbonate, chloride, bromide, acetate, phosphate, &c. Used internally as stimulants, diaphoretics, diuretics, antispas- modics, &c. ; and externally in liniments as rubefacients. Antimony, in several preparations as sulphurated, tartarated, oxide, and chloride. Used internally as diaphoretics, expectorants, &c. ; and externally in unguents as counter-irritants. Arsenic, in many preparations as arsenite of potash, arsenite of soda, arsenite of iron, hydrochloric solution of arsenic, and hydrio- date of arsenic and mercury. Used internally in small doses as an alterative and tonic in skin and nervous affections; and externally as a lotion in cutaneous diseases. Arsenious acid, or the white oxide of arsenic, is a powerful irritant poison. Barium, in solutions of the chloride (a very poisonous salt) as an alterative in glandular affections. Bismuth, in several preparations, as the carbonate, subnitrate, and citrate. Administered internally in solutions, in powder, and in lozenges, as a sedative ; and externally as a sedative. The sub- nitrate forms the well-known cosmetic, " pearl powder." Bromine, in the free state, as a local irritant and caustic, and in the preparation of bromide of potassium, and bromide of ammo- nium ; now largely employed (especially the former) as a remedial agent in nervous affections. Cadmium, in the preparation of the iodide and sulphate. Used chiefly externally as ointments and lotions for scrofulous sores and swellings. Cerium, in the preparation of the oxalate, oxide, and nitrate. Used internally as sedatives and nervous tonics. Chlorine, dissolved in water as a lotion, and inhaled in the form of vapour as a stimulant and irritant. Copper, in the preparation of the sulphate (blue vitriol) and the subacetate (verdigris). The former used internally and exter- nally as an astringent, &c. ; the latter, in powder as an escharotic. Gold, in the double chloride of gold and sodium, is occasionally employed, and appears to -act in a manner similar to mercury. Gold-leaf is used in dentistry for stopping teeth. Iodine, used in the free state, as well as in the preparation of several liniments, lotions, tinctures, and ointments for external applications, in cases of scrofula, tumours, glandular enlarge- ments, and the like ; and inhaled as vapour for bronchial and lung affections. Iron, employed in many preparations as the carbonate, sulph- ate, arseniate, phosphate, perchloride, peroxide, pernitrate, tartrate, citrate, &c., and occasionally in the pure or reduced state. Used chiefly internally in the form of solutions, syrups, pills, and loz- enges, as astringents, tonics, and correctors of the blood. Lead, .in many preparations, as the oxide, iodide, acetate or sugar of lead, subacetate or Goulard's lotion, carbonate, and ni- trate. Applied, for the most part, externally in lotions, ointments, plasters, &c., as sedatives and astringents. Lime, in preparations, as quicklime, prepared chalk, chloride, and phosphate. Used internally as antacids, astringents, antiscor- MINERAL MEDICINES. 26 1 butics, &c. ; and externally as caustics, tooth-powders, and in liniments for burns. The chloride and chlorinated are extensively employed in the preparation of chloroform, and as disinfectants and antiseptics. Lithia, in the preparation of the carbonate and citrate, which are used chiefly in effervescing draughts, as antacids and diu- retics. Magnesia, largely employed in the preparation of the oxide, carbonate, sulphate, citrate, and other salts. Used internally, and chiefly in solutions as antacids, aperients, and purgatives. Manganese, in the preparation of the sulphate and carbonate, which are occasionally employed as purgatives, and in cases of anaemia. The permanganates of potass and soda are largely em- ployed as deodorisers and disinfectants. Mercury has been long and largely used in medicine, partly in the free state, but chiefly in the preparation of such compounds as the subchloride (calomel), the perchloride (corrosive sublimate), ammoniated mercury (white precipitate), iodide of mercury, sul- phide, nitrate, &c. It has also been variously administered, inter- nally and externally, in powder, pill, plaster, ointment, and lini- ment. Its preparations bulk largely in the pharmacopoeia, and have been as variously employed as alteratives, purgatives, in biliary affections, in syphilis, reduction of malignant tumours, in certain skin diseases, &c., &c. Corrosive sublimate is also em- ployed as an antiseptic. Petroleum, employed internally as a stimulant, diaphoretic, and expectorant; and externally in squamous skin diseases and in rheumatism. Carbolic acid is extensively employed as a deodor- iser and disinfectant. Phosphortts, used chiefly in the preparation of phosphoric acid, which is occasionally given in weak solutions as an astringent, and in cases of osseous tumours and scrofulous affections. Potass, in many preparations, such as solution of potass, caus- tic potash, the carbonate, bicarbonate, acetate, citrate, tartrate, sulphate, nitrate, permanganate, bromide, iodide, &c. Adminis- tered in solutions, pills, and lozenges, largely consumed as potash- water, and applied externally as lotions and unguents. Variously given as antacids, sedatives, febrifuges, refrigerants, diuretics, &c. The permanganate is employed as a deodoriser and disinfectant. Silver, in preparations as the nitrate and oxide. Used internally as an astringent, tonic, and alterative ; externally in lotions, as an astringent and irritant the nitrate in the solid state being caustic. Soda, in many preparations, as the carbonate, bicarbonate, sul- phate, sulphite, biborate, tartrate, citro-tartrate, chlorate, and chlo- ride of sodium or common salt. The salts of soda are. largely employed in the manufacture of soda-water, and administered in solutions and lozenges as aperients, purgatives, diuretics, and antacids. Sulphur, as flowers of sulphur and milk of sulphur in confec- tions and ointments. Used internally as a stimulant, laxative, &c. ; and externally as a stimulant, and in skin diseases. Inhaled 262 MINERAL MEDICINES. as vapour ; and employed in weak solutions of sulphuric and sul- phurous acids as a refrigerant, tonic, and astringent. Zinc, in several preparations, as the oxide, chloride, sulphate or white vitriol, carbonate, acetate, and valerianate. Generally em- ployed internally as tonics, astringents, and emetics ; and exter- nally as desiccants, astringents, and escharotics. The chloride (Burnett's solution) is largely used as a deodoriser and disin- fectant. The minerals and metals being described in other chapters, the preceding is the merest summary of those whose prepara- tions are employed in medicine. Some are very sparingly used, and others, as the salts of magnesia, potash, and soda, very largely consumed ; but, whether sparingly or largely, they have all a commercial value, and consequently come within the cognisance of the economic geologist. In many instances their industrial applications are noticed under other heads ; but a summary like the preceding brings them at once under the eye of the student, and enables him better to comprehend the nature and amount of materia medica derived from the mine- ral kingdom. Their preparations and specific applications lie beyond the scope of his science; but the substances from which they are obtained their nature, position, and abund- ance belong exclusively to his research and determination. Works which may be consulted. Neligan's ' Materia Medica ; ' Royle's ' Manual of Materia Medica and Therapeutics ; ' Garrod's ' Essentials of Materia Medica and Thera- peutics. ' XVII. THE GEMS AND PRECIOUS STONES. THE Gems and Precious Stones have always been to man whether savage or civilised objects of the liveliest interest and attraction. Their sparkle and play of colours, their un- tarnished beauty and durability, have ever made them the coveted ornaments alike of the troglodyte of the cave and the prince of the palace. The most gorgeous wreath of flowers scarcely survives the day it is woven, the most brilliant head- dress of feathers is soon sullied and worn, but the necklace or amulet of gems retains its glitter and freshness for generations. No wonder, then, that they have been so universally prized, so long the essential adjuncts of barbaric splendour, and still the most esteemed and precious ornaments of refinement and civilisation. As minerals they bulk very slenderly in the crust of the earth, being druses in veins and fissures, segregated as geodes in the pyrogenous rocks, or developed as accidental or accessory crystals in the older metamorphic strata. In what- ever formation or position they occur, they are never found in masses ; and when found, comparatively few have sufficient purity and brilliancy to render them specially attractive. For this reason most of them retain a wonderful uniformity in value ; and though fashion may occasionally enhance or dimi- nish the demand for certain sorts, yet in the long-run the finer gems and precious stones can ever secure a ready and remu- nerative market. Looking at them from a lapidary's point of view, it were endless, and useless as endless, to enumerate the forms into which they may be cut, or the variety of names by which they are known. Mineralogically, the most esteemed and better known that is, those most abundantly employed in the orna- mental arts can be arranged into a few groups according to their prevailing chemical] constituents ; and to this arrange- ment we shall in the present chapter adhere. The division 2 64 THE GEMS AND PRECIOUS STONES. into Gems and Precious Stones is an old and familiar one, in- cluding under the former the diamond, sapphire, emerald, ruby, topaz, hyacinth, and chrysoberyl and under the latter such as rock-crystal, amethyst, opal, agate, carnelian, jasper, and malachite ; but it is too wide for scientific purposes. The gems or jewels are, no doubt, more select than the precious stones ; but the arrangement conveys no idea of their respec- tive compositions ; and so, without much scientific error, the whole mav be intelligibly ranked as carbons, hydro-carbons, silicas, aluminas, and silicates of alumina, the less known and esteemed being variable compounds of these and other mine- ral substances. I. THE CARBON GROUP. Diamond. Foremost in this group, as among all the other gems, stands the Diamond, so called from its unparalleled hardness (Gr. adamas). It has ever been the most precious of gems, and, chemically speaking, consists of carbon or charcoal in its pure and crystallised form, having a hardness of 10, and specific gravity of 3.5. This form is primarily that of a regular octa- hedron, but of this there are numerous modifications the crystals having often curved faces less or more approximat- ing to spheres. These crystals are cleavable, easily frangible, are not acted upon by acids or alkalies, but burn and are dis- sipated at a heat under the melting-point of silver. They occur loose in alluvial sands and gravels or singly, imbedded in a matrix of sandstone in India, and of mica-slate in Brazil and South America. Geologically, they have been found most abundantly in the old drifts of India and Borneo, Brazil, and the Cape district ; more sparingly, and in minor crystals, in those of the Urals, Carolinas, Mexico, and Australia. The " Diamond Sandstone " of India, which furnishes the detritus in which most of the specimens are found, is said to be of Tertiary origin; the micaceous schists, which yield the dia- monds of Brazil and the Urals, are probably as old as the Cambrian and Laurentian ; while the diamantiferous drifts of the Cape seem to be derived from igneous rocks of Jurassic or later origin. Whatever the age of the original matrix, they are now found at no great depth from the surface in gravelly drifts the cascalho of Brazil being an alluvium consisting of quartzose gravel, stained by oxide of iron, and containing be- sides the diamonds variously-coloured topazes and grains of THE CARBON GROUP. 265 gold ; and that of the Cape consisting of gravelly debris, im- bedding pebbles of rock-crystal, agate, and carnelian. Accord- ing to Dr Gardener (' Travels in Brazil '), the diamond diggings of that country consist of Reddish sandy clay, 20 feet. Tough yellow clay, Coarse reddish sand, Loose gravel (Cascalho*) Hard clay (variable), Schistose rocks, . * Canga when the gravel is compact and conglomerated. Diamonds are found of various colours and in various de- grees of purity, the dark and inferior being known as bort, and the amorphous as carbonado, and only used (see Chap. XI.) as cutting and polishing materials ; the colourless, or those which have some very decided tint (blue or yellow) are most esteemed; those slightly discoloured are the least valuable. Diamonds are cut and polished only by their own dust or powder an art known from remote antiquity in the East, but introduced into Europe only about the end of the fifteenth century, and now centred principally in Amsterdam. They are cut chiefly into two forms rose and brilliant ; the latter having the finest effect, but requiring a greater sacrifice of bulk, some crystals being reduced nearly one-half in weight i. Rose ; 2. Brilliant ; 3. en Cabochon. by the operation. When washed from the matrix, the dia- monds occur in all sizes, from mere points to one or two hun- dred carats (of 3 T / grains each) in weight, larger crystals being extremely rare and often apocryphal. The largest and finest diamonds have hitherto been found in India ; the largest amount perhaps 800 or 1000 Ib. a-year has been procured from Brazil ; but a greater proportion of large stones to small ones has recently been obtained from Africa, though slightly " off colour " as compared with those of India and Brazil. Respecting the origin of the diamond, neither chemistry nor geology has thrown much light on the subject. We know that it consists of carbon in its purest and most concentrated form ; 266 THE GEMS AND PRECIOUS STONES. but whether the carbon is of vegetable or of animal origin, or whether it may not be a purely chemical elaboration altogether apart from organic growth, science has not yet determined. It is true that some observers have thought they detected traces of vegetable structure in the ashes of the diamond, but their observations have not been confirmed; and none of the speci- mens containing foreign matter have as yet given any hint of their formation. It has been remarked that their occurrence in mica-slate does not favour the idea of their immediate vege- table origin, nor does their occurrence in soft quartzose sand- stone indicate the operation of excessive heat. Indeed their combustible nature forbids the idea of intense heat in connec- tion with their formation ; and yet high heat under pressure, or a long-continued low heat manifesting itself in chemical change, may have effected the crystallisation of carbon in decaying organic matter. Chaucourtois (as quoted by Dana) observes that the formation from a hydrocarburetted vapour or gas is analogous to that of sulphur from hydrosulphuretted emana- tions. In the oxidation of the latter by the humid process, the hydrogen becomes oxidised, and only a part of the sulphur changes to sulphurous acid, the rest remaining as sulphur ; so in the humid oxidation of a carburetted hydrogen, the hydro- gen is oxidised, part of the carbon becomes carbonic acid, and the rest remains as carbon and may form crystallised diamonds. Amber. Amber (Arabic), well known as an ornamental substance, is a fossil gum or gum-resin, usually found in connection with Tertiary lignites. In hardness it ranges from 2 to 2.5, is rather brittle, easily cut, of various shades of yellow, from almost pale white to orange brown, and semi-transparent. It is very light (specific gravity 1.08), becomes negatively electric by friction, and burns like other hydrocarbons with much smoke and flame. It consists of about 78 carbon, 12 hydrogen, and 8 oxygen, and frequently encloses fragments of leaves, insects, and the like showing that it must once have been in the state of a gummy or viscous exudation. It occurs in irregular nodules, from the size of a hazel-nut to that of a man's head, the latter size, however, being rare. It is found in Sicily, Poland, Saxony, Burmah, Siberia, and Greenland, in Tertiary clays ; on the Yorkshire coast of our own country ; but in par- ticular on the Baltic coast of East Prussia, where it is thrown up after storms, and strewn along the shore. It is, also, but very seldom, obtained by digging down to the lower beds of THE CARBON GROUP. 267 the Tertiary lignites in North Germany ; and there it occurs in connection with coniferous trunks and branches. These forests of amber-pines (Pinites sucdnifer) seem to have been situated in the north-eastern part of what is now the bed of the Baltic, and were probably destroyed at the commencement of the Drift period. The insects enclosed in the amber cannot be referred by entomologists to living species ; but it has been observed that in their general characteristics they resemble more the insects of warm climates than those of temperate latitudes. As an ornamental substance, amber was at one time much more valued in this country than now j but it is still highly prized in the East, and some of the pale-yellow translucent pieces bring extravagant prices. It has been, and is still, employed in the manufacture of necklaces, bracelets, ear-drops, toilet-boxes, cane-handles, mouth-pieces of pipes, and other small works of art; and industrially for the distillation of succinic acid and the oil of amber the residue forming the basis of one of the finest black varnishes. Ambrite. Ambrite is the name given by Dr Hochstetter to a fossil or sub-fossil resin occurring in the soil of the province of Auck- land, New Zealand, and somewhat resembling amber in colour and quality. It is found in pieces from the size of a hen's egg to that of the head, and consists of about 77 carbon, 10 hydrogen, and 13 oxygen. It resembles the resin of the Australian pine (Dammara Australis), but wants the rich colour and trans- parency of amber. Some of the finer pieces have been manu- factured into ornaments ; but its principal use is in the prepara- tion of varnishes. Jet. /<#, so extensively used for personal ornaments, is a compact, highly lustrous variety of lignite, deriving its name (jayet, gagita) from Gaga, a river in Asia Minor, whence it was ob- tained by the ancients. It occurs in many countries Turkey, Spain, France, Prussia, England and in formations ranging from the Tertiary to the Lias inclusive. It is found in lumps and branch-like fragments the coarser pieces often revealing their ligneous texture ; while the fine are of an intense velvety black, compact, resinous in lustre, and breaking with a conch- oidal fracture like asphalt. It is almost as light as amber, is electric when rubbed, sectile, but rather brittle, and requires delicate handling. Jet is largely manufactured for mourning ornaments, for ear- 268 THE GEMS AND PRECIOUS STONES. drops, beads, rosaries, necklaces, buttons, bracelets, clasps, rings, and other articles of personal decoration. In France, the departments of Aude, of the Var, the Pyrenees, of Ariege, and of Ardennes, are celebrated for this manufacture, which is also carried on, though to a less extent, in Northern Germany. In our own country, Whitby in Yorkshire is the head-centre of production, the raw material being obtained in great purity and beauty from the bituminous shales of the Upper Lias in that locality. About ^20,000 is mentioned as the annual value of the Whitby manufactures. Jet is occasionally imitated by glass and vulcanite, bat the imitation is readily detected by the greater weight and hardness of the former, and by the inferior lustre and sulphurous odour of the latter, when rubbed or held for a while in the warm hand. Dogwood. Oak and other hard woods that have lain long in peat-bogs and marshes containing iron, assume a dark hue from the action of the metal on their tannin. Trunks of fine and firm grain, when slowly dried and skilfully cut and polished, make handsome mourning ornaments, as brooches, bracelets, beads, &c. Irish bogwood, which is often intensely black (though its colour can be artificially heightened), set with rock-crystals (Irish diamonds), was at one time much sought after for such purposes. Many of the so-called "bogwoods," however, are merely stained imitations. Cannel-Coal. Some of the more compact varieties of Cannel-Coal have, like jet, been manufactured into necklaces, brooches, vases, candle- sticks, table-tops, and the like, but these more as objects of local curiosity than as articles of regular trade, for which the inferior texture and lustre of the material renders it unsuitable. II. THE ALUMINA GROUP. Corundum, or Corundum-stone (Hindoo, Korrund) is the name given to crystallised forms of alumina, and consists of from 95 to 98 alumina and 3 water, with traces of lime, silica, and magnesia. It usually occurs in six-sided prisms, and in obtuse and acute six-sided pyramids, but is likewise found granular and massive, having a hardness of 9, and a specific gravity of 4. It is chiefly of a greyish or greenish tint, but is THE ALUMINA GROUP. 269 sometimes nearly colourless and slightly translucent ; uneven in fracture, tough when compact, and the hardest of all known minerals except the diamond. It occurs in the old crystalline rocks granites, gneisses, mica-shists, quartzites, and crystal- line limestones, and is found in India, China, Asia Minor, Scandinavia, and the United States especially in North Carolina, where it occupies veins in serpentine, traversing the country for nearly 200 miles. Indifferent specimens are said to occur in Cumberland, Cornwall, and the Mourne Moun- tains. "The name corundum" says Mr Bristow, "is commonly confined to the opaque rough crystals and cleavable masses, generally of a dingy colour, and often dark ; while the term emery embraces the more or less impure, massive, granular, and compact kinds; and sapphire and ruby comprises the transparent, brightly tinted varieties." Only the transparent and tinted varieties are employed as gems : the opaque and massive sorts reduced to powder are used for polishing and cutting, as already noticed in Chapter XL Ruby. Ruby (from the Lat. rubeo, to flush with red) is a mineralo- gical as well as lapidary's term for the fine red transparent varieties of spinel and corundum. The finest red and violet varieties are obtained from Ceylon, Ava, Burmah, and other parts of the East, hence known as Oriental Ruby ; and when uniform in colour, free from flaws, and large, rank next to the diamond among gems. Restricting the name Ruby to the red transparent varieties of corundum, it is customary to speak of the full carmine-red as Spinel Ruby ; the pale rose- red, as Solas Ruby ; the orange-red, as Vermeille ; the yellow- ish-red, as Rubicelle; and the violet, as Almandine ; but of course there are many intermediate shades, as there are diver- sities of composition, among the so-called "rubies" of the lapidary and jeweller. The " corundums " proper consist almost entirely of alumina, with minute but varying propor- tions of iron peroxide or other colouring matter ; the " spinels," on the other hand, contain from 10 to 20 per cent of magnesia, with minute but varying proportions of silica, lime, and iron hence their superior hardness. The rubies are generally set in rings, brooches, and other personal ornaments, and surrounded by brilliants. They bring high prices, a perfect ruby of i carat being worth, it is said, 10 guineas; of 2 carats, 42 guineas; of 3 carats, 100 guineas; and of 6 carats, above 1000 guineas. 2/O THE GEMS AND PRECIOUS STONES. Sapphire. Sapphire (Gr.) is the name usually given to brightly coloured varieties of corundum, other than the red or oriental ruby. The blue are generally called Oriental Sapphire; the trans- parent or translucent yellow or white, Oriental Topaz ; the green, Oriental Emerald ; the violet, Oriental Amethyst ; the hair-brown, Adamantine Spar; when transparent, with a pale reddish or bluish reflection, Girasol Sapphire ; and with pearly opalescence, Chatoyant or Opalescent Sapphire. Like the rest of the corundum family, the sapphire consists chiefly of alu- mina (98.5, according to Klaproth), with traces of iron peroxide and other colouring matter. It occurs in prismatic crystals in the crystalline rocks of Ceylon, Burmah, India, Bohemia, the United States, and other countries, but is chiefly found in rolled pebbles in the detritus of streams and river-courses. As already mentioned, sapphire is the hardest of known substances except the diamond. It is therefore cut by means of diamond-dust, and polished on copper and lead wheels with emery-powder. A good stone of 10 carats is said to be worth ^50, and one of 20 carats, worth ^200. Turquois. The Turquois, of which there are two sorts the Oriental or Mineral Turquois, and the Occidental or Bone Turquois when cut in \ovfcabochon, is much employed in jewellery on account of its beautiful tone of colour (a peculiar blue or bluish-green), which contrasts well with diamonds, pearls, and gold. The mineral turquois is a hydrous phosphate of alumina, with phos- phate of lime, silica, and oxides of copper and iron 47 alu- mina, 27 phosphoric acid, 3 phosphate of lime, 2 oxide of copper, i peroxide of iron, and 19 water. The finest speci- mens have hitherto been obtained from Persia, Tibet, and Arabia, where it is said to be imbedded in sandstones of un- known age. The bone turquois, or odontolite, on the other hand, is merely bone or ivory coloured sky-blue or bluish- green by phosphate of iron, and is chiefly obtained from the sub-fossil deposits of ivory in northern Asia, the mammoth- drifts of Siberia and the adjacent islands. The turquois is much esteemed as a setting on account of its fine uniform blue, which is unimpaired in gas or candle light. It is often imitated ; but the solid subdued tone of the real gem is readily distinguished from the vitreous lustre and gloss of the paste imitation on the one hand, and from the flawed-like aspect of odontolite on the other. Besides, odonto- lite effervesces with acids, gives out a fetid odour when heated, and is also inferior in specific gravity. THE SILICA-ALUMINA GROUP. III. THE SILICA-ALUMINA GROUP. Topaz. The silicates of alumina constitute a numerous class of minerals ; but only those of fine colours and translucency are ranked among the gems. One of the most esteemed is the Topaz so called, it is said, from its being obtained by the ancients from Topazos, an island in the Red Sea. In com- position, it is a fluo- silicate of alumina, occurring in finely streaked prismatic crystals, transparent in various degrees, vitreous, electric when heated or rubbed, and of various colours or colourless the yellow, blue, and white being the most esteemed. It is also found in indistinctly crystalline masses and rounded fragments. It occurs chiefly in the granitic and crystalline rocks, mostly in drusy cavities, and frequently associated with rock-crystal, tourmaline, and beryl, or with fluor-spar and. other minerals containing fluorine. It stands 8 in] the scale of hardness, and has a specific gravity of 3.5. A specimen from Saxony yielded to Berzelius 34.24 silica, 57.38 alumina, and 14.99 fluorine. The topazes are highly valued as ornamental stones, and are often of large size compared with other gems. The chief supplies are obtained from Brazil and Siberia, though good specimens are also occasionally procured from Burmah, Ceylon, Asia Minor, Bohemia, the Scottish Highlands, Mourne Moun- tains, Mexico, the United States, and Australia. Those from Brazil have generally deep yellow tints, but become pink or pale crimson on exposure to heat; and many "Brazilian rubies " are said to be merely topazes that have been success- fully treated in this way. The blue or "Brazilian sapphire" of the lapidary is simply a topaz of a deep celestial blue, which has a fine effect when well cut and set ; and the colourless and transparent from the same region, known as gouttes (Feau, or drops of water, when skilfully facetted, is said to come close to the diamond in lustre and brilliancy. Those from Siberia have usually a bluish tinge resembling aquamarine, and are often very limpid and transparent. The Saxon topazes are of a pale wine-yellow ; and those found in the Scottish Highlands of a sky-blue, often with a tinge of reddish-brown. Indeed the topazes are very variable in colour and transparency, resembling in this respect the rock-crystals, from which, how- ever, they may be distinguished by their greater hardness and more vitreous lustre. 2/2 THE GEMS AND PRECIOUS STONES. Emerald. The Emerald, which has long ranked high as a gem, is generally of a rich deep-green colour; the less brilliant and colourless varieties being known as beryls. The crystals occur in hexagonal prisms, rarely in columnar aggregates, and usually marked with longitudinal striae. They are transparent to sub translucent, rather brittle, 7.5 in hardness, and 2.7 in specific gravity. The emerald is found either imbedded or in druses, in most countries in the old crystalline rocks ; but in the celebrated modern locality of Muzo, New Granada, in a Secondary limestone abounding in ammonites. The finest speci- mens are brought from South America ; but fair varieties have been found in Columbia, Norway, Abyssinia, India, and Siberia. According to Vauquelin, who, in analysing the emerald, first discovered the earth glucina, the purest specimens consist of 65 silica, 14 alumina, 13 glucina, 2.56 lime, and 3.50 oxide of chromium, to which last the gem was supposed to owe its fine green colour. According to the more recent researches of M. Lewy, however, the colouring matter is considered to be a carburet of hydrogen, and of animal origin: a supposition to which its presence in the fossiliferous limestone of Muzo gives great support. The colour of the emerald can easily be destroyed by heat a circumstance which does not occur in those gems that are coloured by oxide of chromium. As a precious stone, the emerald is said to rank next to the ruby in value. It may be distinguished from all other gems by its pure unbroken green. It is usually table-cut ; and ap- pears to greatest advantage when surrounded by brilliants, the lustre of which contrasts agreeably with its own quiet tints. Beryl. Beryl (Lat. beryllus) is the mineralogical as well as the lapi- dary's term for the less brilliant and colourless varieties of the emerald. The finest beryls or aquamarines (so called from their sea-green tints) are found in Siberia, chiefly in druses or veins in granite, along with rock-crystal, or tourmaline, and topaz. Some crystals exceed a foot in length and several inches in diameter, but others of still more gigantic dimensions have been found in the United States. Esteemed gems also occur in the granite of Wicklow and Aberdeen, in Norway, Bavaria, the tin-mines of Bohemia, Brazil, and many other localities. When pure, aquamarine is much esteemed in jewellery, espe- cially in ornamenting articles of dress, and the ancients em- ployed it occasionally in the engraving of medallions. " Pebbles of quartz," says Bristow, " are sometimes taken THE SILICA-ALUMINA GROUP. 273 for beryls, and vice versa. The two may be distinguished by observing that the crystals of beryl are striated longitudinally, while those of quartz are striated transversely, or at right angles to the axis of the prism. Moreover, the fracture of the two minerals is widely different; for the beryl breaks in smooth planes, the faces of which are at right angles to the axis of the crystals, whereas the fractured surface of quartz is invariably conchoidal." Lapis Lazuli. Lapis Lazuli is a well-known mineral of an ultramarine or fine azure-blue colour, of various intensity. When crystallised it occurs in dodecahedrons, but is generally found massive and disseminated; of a finely granular or compact texture, hardness about 5.5, and specific gravity 2.4. It varies con- siderably in composition ; but, on the whole, may be said to consist of from 45 to 50 silica, 30 to 32 alumina, 6 sulphuric acid, 9 soda, with minor and varying proportions of lime, iron peroxide, chlorine, and sulphur. The depth of the colour seems to depend on the amount of iron and sulphur. It is found chiefly in crystalline limestones, but occurs also in the granitoid and crystalline schists. The finest specimens are ob- tained from Siberia, China, Tibet, and Tartary. When suf- ficiently large and pure it is employed as an ornamental stone; but its chief use is in the preparation of the fine pigment called ultramarine, as already noticed in Chapter XIII. Lapis lazuli takes a pretty good polish, and notwithstanding its deficiency in lustre, the beauty of its colour has caused it to be used in jewellery, generally for brooches, clasps, ear- drops, ring-stones, and shirt-studs. It is seldom employed for seals on account of its softness. The more richly coloured varieties are used for mosaics, and are also fashioned into vases and other costly ornaments. Felspars. To these more valued silicic-aluminous gems may be added several of the Felspars, which occasionally exhibit a fine opales- cent play of colours. Among these may be noticed Adularia felspar, or moonstone, a translucent potash variety, which, when cut en cabochon, displays a pale-blue opalescence ; Labrador felspar, or Labradorite, a soda-lime variety, which produces a pearly iridescence when light falls on it in certain directions : Amazon-stone, another potash variety, of a bluish-green or sometimes verdigris green, exhibiting when cut a peculiar spangly iridescence ; and variolite, a dark-green variety, con- taining disseminated sphericles of a paler hue. Most of these S 274 THE GEMS AND PRECIOUS STONES. felspars are found of considerable size, and are well fitted for inlaid work, and for the manufacture of caskets, snuff-boxes, and similar ornaments. Garnets. The Garnets constitute an extensive and extremely variable family, according as alumina, iron, lime, magnesia, or similar bases are associated with the silica which composes about half the mineral. They are all, in fact, silicates of one or more of these bases, and are usually arranged into six sections viz., alumina -lime garnets, alumina - magnesia garnets, alumina- iron garnets, alumina - manganese garnets, iron-lime garnets, and lime -chrome garnets. They occur chiefly in gneiss, mica-schist, and other crystalline strata, but are found also in granite, trap, and other igneous rocks. The garnet proper appears in dodecahedral crystals and druses, in grains, and occasionally massive, or so thickly interspersed in the gneiss or mica-schist as to become garnet-rock, and in this case, when crushed to powder, employed as a cutting and polishing material under the name of "red emery" (Chap. XL) The hardness of garnet varies from 6 to 7, and its specific gravity from 3 to 4. In colour it is usually deep amber-red, reddish -brown, or black, but occasionally olive-green passing into yellow ; its lustre is resinous or vitreous ; and it is transparent in all degrees. Of the better known and more valuable varieties we may men- tion the Almandine, or noble garnet, of a beautiful columbine- red; the Grossalar, or olive-green; the Hessonite, or Cinnamon- stone ; the Colophonite, or resinous garnet; the Pyrope, Fire- garnet, Alabandine, or Carbuncle (when cut en cabochori] ; and the Topazolite. Garnets have a world-wide distribution, but those of commerce are chiefly obtained from Bohemia, Ceylon, Pegu, and Brazil. They are extracted from the matrix; gathered from river-drifts; and occasionally, as near Elie in Fifeshire (Elie rubies), found in the shore-sands which fringe the trap-tuffs from which they are weathered and detached. "Garnet," according to Bristow, " is easily worked, and, when facet-cut, is nearly always (on account of the depth of its colour) formed into thin tables, which are sometimes concave, or hollowed out on the under side. Cut stones of this latter description, when skilfully set with bright silver-foil, have often been sold for rubies." Zircons. The Zircons, of which there are several varieties fazjargoon, colourless or smoky, the hyacinth, bright red or reddish-orange, THE SILICA GROUP. 2/5 and the zirconite, reddish-brown are valuable gems, consisting of about 66 zirconia and 34 silica, having a hardness of 7.5, and specific gravity of 4.5. They occur in the older meta- morphic and granitic rocks, and are found in Ceylon, Italy, Saxony, Scandinavia, Scotland, Canada, and Greenland. The Cingalese jargoon is a highly lustrous variety, known as the " Matura diamond," and occasionally sold for the real gem ; and the bright red of the hyacinth renders it suitable for finger - rings and pendants. Though less in fashion than formerly, the zircons form bright and durable ornaments, being perhaps the least alterable of minerals. It was in the zircon that Klaproth discovered the earth zirconia, in 1789. IV. THE SILICA GROUP. The Silicious Gems or Quartzes present a very numerous family, but here we have to deal only with the more trans- parent, lustrous, and brilliantly coloured varieties. These, without much scientific error, may be arranged into four sections : i. The Vitreous, or those which have a bright glassy lustre as rock-crystal, rose-quartz, siderite, cairngorm, amethyst, avanturine, &c. ; 2. The Chalcedonic, or those which display the subvitreous or waxy lustre and transparency of chalcedony as agate, carnelian, chalcedony, onyx, &c. ; 3. The Opaline, or hydrous varieties, having the resinous lustre and semi - transparency of opal as fire-opal, hyalite, cacholong, &c. ; and 4. The Jaspery, or those presenting the duller colours, lustre, and opacity of jasper as blood-stone, jasper, Lydian stone, and the like. Rock- Crystals. Rock-crystal, though usually colourless and transparent, occurs in various shades, and the term is even extended to smoke-coloured and perfectly black varities. It is customary, however, to distinguish the coloured varieties by separate names; hence the violet-blue are known as amethysts; the wine-yellow, topazes ; the cinnamon-yellower \XGwn.,cairngorms ; the indigo-blue, siderites ; -the reddish-pink, rose-quartz ; and so forth. Rock-crystal is found in veins, fissures, and other cavities in every geological formation, but chiefly and most perfectly in the older crystalline and granitic rocks. The primary form is rhombohedral ; but it usually occurs either in six-sided prisms, acutely terminated by six planes ; in acute, simple, six-sided prisms ; or in such prisms and pyramids doubly 2/6 THE GEMS AND PRECIOUS STONES. terminated. The largest and finest specimens are obtained from the Alps, Pyrenees, Siberia, Brazil, Ceylon, Madagascar, ancl in a less degree from Saxony, Norway, Ireland, and the Scottish Highlands. The purest sorts consist almost entirely of silica (99 and upwards), with a trace of alumina, lime, iron oxide, or other colouring matter ; have a fine vitreous lustre, a specific gravity of 2.5 to 2.8, and a hardness of 7, being in this respect only inferior to the topaz, corundum, and diamond. The purest colourless varieties are cut into spectacle-lenses, and also largely used as gems under the names of Bohemian diamonds, Irish diamonds, Bristol diamonds, &c. Some highly transparent crystals, when skilfully cut, have a wonder- ful sparkle, and were extensively used when shoe-buckles, knee-buckles, and similar ornaments were more in fashion. Larger crystals are cut into seals, cups, vases, pendants, buttons, and the like ; and fair specimens are said to be worth from five to twenty shillings a pound, according to size and transparency. The amethystine varieties (coloured by the oxide of manganese) are more highly prized for personal ornaments, but lose their tints under gas or candle light. The cairngorms (from the mountains of that name in Banffshire), when of fine hue, are much valued for brooches, bracelets, ear-drops, seal-stones, and other objects of jewellery; and it is stated by Nicol in his ' Mineralogy/ that at one time an Edinburgh lapidary cut ^400 worth out of a single crystal ! Green and red varieties, when skilfully cut and polished, also furnish handsome stones the latter, under the name of " Bohemian ruby," being some- times passed off for the spinel ruby, though naturally inferior in lustre and hardness. There are other varieties, such as asteriated (star-quartz), avanturine (spangled-quartz), &c., used for ornamental pur- poses; but to notice all would be to present a lapidary's catalogue of stones which differ only in some slight peculiarity of colour or structure, while essentially the same in nature and origin. Those imbedding minute crystals of other minerals and metals are often very pretty ; and by heating quartz, and plunging it it in coloured solutions, curious effects in colour and lustre can be produced, which are apt to be mistaken for natural appear- ances. Calcedonies. The Calcedonic or semi-pellucid varieties calcedony, agate, carnelian, onyx, &c. have long been employed for ornamental purposes. Calcedonies (Chalcedon in Asia Minor) of fine uniform colour are prized for seals their toughness allowing THE SILICA GROUP. 277 them to be cut with great clearness and precision. Chryso- prase (Gr. chrysos, gold ; prasos, leek) is a fine apple-green or yellowish-green variety of calcedony, owing its colour to a small percentage of nickel oxide. Though not much used in this country, chrysoprase is highly valued in Germany and the East, where it is cut into brooches, ring-stones, seal-stones, bracelets, and other kindred ornaments. Geologically, the calcedonies proper occur in geodes and vein-bands, but more frequently as an incrustation or sinter, having a wavy internal structure and mammillated surface. The agates, found mostly in geodes in the amygdaloidal trap-rocks, or in gravels derived from these rocks, occur in many varieties ribbon or striped agates ; fortification-agates, showing the alternating bands in zigzag arrangement, like the plan of a fortification ; brecciated agates, as if composed of cemented fragments ; moss-agates, exhibiting minute den- dritic ramification like moss-growth, &c. The name, ac- cording to Theophrastus, is derived from Achate, a river in Sicily, where fine varieties were found ; but others think it more probably a corruption of the Punic and Hebrew word nakad, spotted, in allusion to their varied colours. The finest agates are usually designated oriental; the moss-agates, Cambay- stones, or Mocha-stones from Mocha in Arabia ; and the banded varieties, as Scotch pebbles, from their frequent occurrence in the traps of Scotland Kinnoul Hill near Perth, the Ochils, and Usan shore near Montrose, being well-known localities. The colouring matter of agates being due to metallic oxides, factitious colours of greater intensity can be produced by boil- ing in various chemical solutions. The agates are cut for brooches, ear-pendants, beads, seal-stones, and the like ; and also, when of large size, for vases, snuff-boxes, knife-handles, mortars, burnishers, and similar objects. Besides those found in Scotland, agates to the value of ^6000 or ,7000 are annually imported from India, Saxony, and other countries. The great emporium of the agates and carnelians, cut and uncut, is Cambay, from which they are sent to all parts of the world. Their finding and treatment is thus described by Forbes in his * Oriental Memoirs : ' Carnelians, agates, and the beautifully variegated stones improperly called Mocha- stones, form a valuable part of the trade of Cambay. The best agates and carnelians are found in peculiar gravelly strata, 30 feet under the surface, in a small tract among the Rajepi- plee Hills, on the banks of Nerbudda. They are not to be met with in any other part of Gujerat, and are generally cut and polished in Cambay. On being taken from their native 278 THE GEMS AND PRECIOUS STONES. bed, they are exposed to the heat of the sun for two years ; and the longer they remain so exposed the brighter and deeper will be the colour of the stone. Fire is sometimes substituted for the solar ray, but with less effect, as the stones frequently crack, and seldom acquire a brilliant lustre. After having undergone this process, they are boiled for two days, and sent to manufacturers at Cambay. The agates are of different hues ; those generally called carnelians are dark, white, and red, in shades from the perfect yellow to the deepest scarlet." The carnelians, so called from their reddish flesh-colours, are generally of uniform tint or clouded, but not striped and banded like the agates. They occur in the same way as agates, and are mostly used for the same purposes, some varieties being well fitted for engraving, and others taking on a very fine and durable polish. The onyxes, so called from a fanciful resemblance to the hues of the human nail, are banded varieties, the alternating bands differing in hue, and thereby rendering them especially fitted for the manufacture of cameos, the lighter layer being carved in relief, while the darker forms the background to the figure. Sard and sardonyx are mere varieties the former in bands of brown, red, and white ; the latter, as its name implies, in alternating bands of sard and onyx. Brown and white, red and white, green and white, are the most frequent alternations of colour ; but these can be intensified by boiling the stone for several days in honey and water, and then soak- ing it in sulphuric acid. Opals. The Opals, or Opaline varieties, are, as already stated, hydrous silicas, consisting of from 90 to 95 of silica, with from 5 to 10 of water, and coloured by traces of iron peroxide, potash, soda, lime, alumina, &c. They are of various colours, milk-white, pearl-grey, reddish-brown, and green ; have a vitreous or resin- ous lustre ; and often exhibit a beautiful play of colours by refracted and reflected light. They are widely distributed in connection with the igneous rocks, and chiefly as concretions, sinters, and incrustations. Bohemia and Mexico yield esteemed varieties, and fair specimens are occasionally found in Corn- wall and Antrim. There are many varieties, some of which are highly esteemed by the lapidary and jeweller. The better known are i. Precious or noble opal, exhibiting a beautiful play of colours ; 2. Hydrophane, or those sub- varieties of noble opal which become transparent on being immersed in water; 3. Sun or fire opal, or girasol, transparent, MISCELLANEOUS GROUP. 279 and having a brilliant vitreous lustre, and generally of a bright hyacinth-red when held between the eye and the light ; 4. Hyalite, or glassy opal, occurring in very glassy, transparent, mammillary incrustations ; 5. Common opal, semi-transparent, and of various colours ; 6. Semi-opal, duller and less pellucid ; 7. Cacholong, or mother-of-pearl opal, having a pearly resinous lustre ; 8. Wood opal, or wood converted into opal by silicious infiltration, and of fibrous structure ; 9. Menilite, or liver opal, a compact semi-resinous variety, from Mount Menil, near Paris: and 10. Jasper-opal, or such ferruginous varieties as pass imperceptibly into common variegated jasper. Jaspers. Thejaspery varieties of quartz are all less or more opaque, and appear striped or mottled in many colours red, yellow, brown, green, grey, white, and black. From their colours, they are usually known by such terms as striped, ribbon, clouded, yellow, red, mottled, or Egyptian. All the varieties are tough, and most of them are coloured by the oxides of iron ; they are found abundantly in veins, bands, and nodules, in rocks of all ages ; and some varieties, like the " porcelain- jaspers," are evidently beds of slaty shale, altered by the action of heat dykes and overflows of basalt, or even in coal-mines which have been on fire. Most of them are susceptible of a fine polish, and are largely manufactured into brooches, brace- lets, snuff-boxes, vases, knife-handles, inlaid work, and other ornamental articles. Though some of the finest varieties are brought from Asia Minor and Egypt, very beautiful specimens are found in Ayrshire (yellow mottled), on the coasts of Forfar, Kincardine, and BanfTshire (red and green, striped and mottled), and on the Dunbar coast (deep-red, banded, and variously mottled). One of the most esteemed is the heliotrope or jasper blood-stone, having a green ground with deep red spots ; fine specimens of which are found in Siberia, India, Transylvania, Bohemia, and occasionally in Italy, Ireland, and Scotland. V. MISCELLANEOUS GROUP. Under this section we include such mineral substances as cannot be properly arranged under any of the preceding groups, and yet which are occasionally employed in jewellery and the ornamental arts. One of the best known of these is Malachite, the green carbonate of copper, consisting of 71.8 copper protoxide, 20 carbonic acid, and 8.2 water, and deriv- 280 THE GEMS AND PRECIOUS STONES. ing its name from the Greek malache, the marsh-mallow, in allusion to its colour. It occurs in copper-rnines in reniform, concretionary, and stalactitiform masses, more or less compact, and in concentric bands of various shades. When cut and polished, it is highly prized for ornamental purposes brooches, snuff-boxes, vases, inlaid work, &c. ; but its softness renders it of less value than it would otherwise be to the lapi- dary and jeweller. The finest specimens are obtained from Siberia, the Urals, and Burra Burra in Australia. For other ornamental stones, not strictly regarded as " pre- cious," the student is referred to Chapter V. VI. PASTES, OR ARTIFICIAL GEMS. From their rarity and value, the gems and precious stones very early became the objects of imitation, and this often with considerable success. As chemistry advanced the imitations became more perfect, and now factitious gems are frequently produced which require all the skill of an expert to detect. These artificial products are made of very pure, fusible, trans- parent, and dense glass, termed strass or paste, with the addi- tion of metallic oxides to impart the necessary tints. This strass consists of silica, alumina, oxide of lead, and potash, with traces of borax and arsenious acid 'to increase its clear- ness and brilliancy. The success of an artificial stone depends chiefly upon the exact imitation of the tint of the real stone, but also in no small degree upon the cutting, polishing, set- ting, and foiling. Being essentially a glass, the artificial pro- ducts differ from the natural in hardness, specific gravity, and power of conducting heat, and may be detected by their in- feriority in these important properties. The hardest glass rarely exceeds 5, while the gems range from 7 to 10 ; glass seldom exceeds 2.5 in specific gravity, the gems range from 2.6 to 4.5 ; glass has not the same cold feel when touched by the tongue, its conductivity being inferior to that of the pre- cious stones. In the preparation of pastes, the ingredients are separately reduced to a fine powder, then mixed and sifted, next carefully fused, and ultimately allowed to cool very slowly. The more tranquil and continuous the fusion, and the more gradual the cooling, the greater is the density and beauty of the product. The proportions of the admixtures and their treatment are strictly matters of chemistry and technology; but we may notice a few to show that they are wholly mineral and metallic, PASTES, OR ARTIFICIAL GEMS. 28 1 and in this respect come within the cognisance of Economic Geology. The imitation of the diamond is obtained by pure silex 100 parts, red oxide of lead 150, calcined potash 35, cal- cined borax 10, and oxide of arsenic i part; the topaz by 1000 strass, 40 antimony, and i purple of cassius ; the ruby by TOGO strass, 5 peroxide of manganese, and a trace of purple of cassius; the emerald by 1000 strass, 8 oxide of copper, and 0.2 oxide of chromium; the sapphire by 1000 strass and 15 oxide of cobalt; the amethyst by 1000 strass, 8 peroxide of manganese, 5 oxide of cobalt, and 0.2 purple of cassius ; the beryl by 1000 strass, 7 glass of antimony, and 0.4 oxide of cobalt ; the carbuncle by 1000 strass, 500 glass of antimony, 4 purple of cassius, and 5 peroxide of manganese ; and so on with many others different fabricators using different propor- tions, according to their success in the imitation. Occurring in drusy cavities as geodes and as accessory minerals, the gems and precious stones do not bulk largely in the rocky crust, but appear (as the Arabic poet has it) merely as " the blossoms of the mineral kingdom ; " hence the high esteem in which they have ever been held, and the uniform values they have maintained. In early times they were procured principally from the East, and the term " Oriental ;> was and is still regarded as a mark of distinction ; but in recent times they have been obtained from the Urals, from Mexico, Brazil, and Southern Africa, in equal purity and per- haps in greater abundance. Notwithstanding these new sources of supply, their money value has been little affected ; the diamonds of Brazil, and more recently those of the Cape, though increasing the numbers, scarcely, if at all, diminishing the price of these, the most brilliant of mineral productions. This arises partly from the greater demand, and partly from the greater wealth of modern society; and as these are eVer increasing factors, there is little likelihood of the gems and precious stones falling much in value, any more than they are likely to fall in favour for their brilliancy and beauty. The practical geologist has thus every incentive to search ; and as new regions are every year being more minutely ex- plored, new sources of supply may reward his diligence, just as we have seen within the current century the gold-fields of California and Australia, and the diamond-fields of the Cape, made known through the keener and more intelligent observa- tion of their first discoverers, The Earth is an exuberant and undenting mother, but she does not thrust her bounties upon her children; and if they would enjoy these, they must make 282 THE GEMS AND PRECIOUS STONES. intelligent endeavour to discover and reasonable effort to secure them. The structure of the globe is better known now than it was fifty years ago, the relations of the rock-formations are more fully understood, and their respective constituents more minutely determined ; and thus the researches of the geo- logist become more definite, and his commercial success more certain. The discovery of a coal-field may, in many respects, be more important than that of a diamond-field ; but while it takes the skill and labour of generations to develop the re- sources of the one, the treasures of the other may be revealed during the toil of a single summer. It is this suddenness, this condensation of wealth within the least possible sphere of time and labour, which becomes the great incentive to gem-hunt- ing; and though often hazardous and uncertain, there is no reason why correct observation and sound deduction should not reduce such uncertainty to a minimum. Works which, may be consulted, Dana's 'System of Mineralogy;' Bristow's 'Glossary of Mineralogy;' Jackson's ' Minerals and their Uses ;' Greg and Lettsom's ' Mineralogy of Great Britain and Ireland. ' XVIII. THE METALS AND METALLIC ORES. THERE is no chapter in Geology more interesting than that which deals with the Metals and Metallic Ores. These sub- stances lie at the foundation of all the higher arts and indus- tries, and little progress can be made, even in civilisation, without some acquaintance with their nature and uses. Man restricted to tools and implements of wood, bone, or stone, can never successfully combat with the forces of nature, or modify them to his service and comfort. He is essentially a savage. But the moment he can arm himself with a weapon of metal, or handle a metallic tool, he gains an ascendancy over external nature, and his course, mentally as well as physically, is there- after onwards and upwards. He always passes through the successive stages of stone, bronze, and iron; and not till he has arrived at the last can he be said to possess tools, implements, and machinery sufficient for the arts and industries of civilised existence. To the metals man owes his finest and most efficient tools, implements, and machinery; his most beautiful and durable ornaments; his most brilliant dyes and pigments; his most convenient medium of exchange; and, indeed, very much of that power which, as an intelligent being, he exercises over the domain of nature. They run through all his arts and in- dustries his endless machinery, instruments, and apparatus his steam-engines, railways, ships, and telegraphs. In fine, there are few or none of his economic processes in which they do not directly or indirectly bear a part. As they are found in nature, it is usual to speak of them as Native Metals and Metallic Ores that is, as metals occurring in a pure and simple state, or as metals chemically combined with other substances thus forming oxides, sulphides, carbonates, silicates, and the like. In the present chapter we shall direct attention princi- pally to their geological recurrence, their abundance, and the 284 THE METALS AND METALLIC ORES. facilities with which they can be procured, leaving the pro- cesses by which they are reduced, smelted, alloyed, and mani- pulated, to the metallurgist and technologist. I. NATIVE METALS. Comparatively few of the metals occur in a free or uncombined state that is, as pure and simple elementary substances. Those most frequently found are gold, platinum, palladium, silver, mercury, copper, arsenic, antimony, bismuth ; and those less frequently and doubtfully iron, lead, zinc, and tin. There also occur, though less abundantly, a series of double-metals, or amalgams of gold and mercury, of silver and mercury, of gold, silver, and mercury, of platinum and iridium, of iridium and osmium, and the like ; but these we need not especially refer to. Gold. Gold, so well and widely known, occurs in various shades of gold yellow, has a hardness from 2.5 to 3.0, and a specific gravity from 16.0 to 19.5, according to its purity. It has ex- treme permanence in air and fire, being little tarnished by any amount of exposure, and melts at 2016 Fahr. It is also extremely malleable and ductile, its malleability being such that it may be beaten into leaves not more than Troyinnr f an inch in thickness, and its ductility so great that one grain is capable of being drawn out into 500 feet of wire. It readily forms alloys with other metals ; and in coinage, as well as in the arts, is generally so alloyed (with copper, silver, &c.) to improve its hardness, and so render it better able to resist the tear and wear of circulation, handling, and cleaning. If 24 carats be taken as the standard of purity, any stated number below 24 will indicate the amount of admixture. Gold is not acted upon by the common acids, but yields to chlorine and nitro-muriatic acid, forming a chloride of gold which is soluble in water. Geologically, gold is a widely distributed metal, and occurs, with few exceptions, in quartz-veins which traverse the meta- morphic or older schistose and slaty rocks. It appears in minute disseminated particles, in scales, strings, arborescent plates, and in nuggets from a few grains to many pounds in weight. When not found in situ in the veinstone, it is usually distributed in stream-drifts of sand and gravel which have been wasted and worn, and transported in course of ages from the mountain-veins to the valleys below. It was from such drifts NATIVE METALS. 285 that the ancients gathered their gold in dust, and scales, and pellets ; and it is still from such deposits in the Urals, Cali- fornia, Australia, New Zealand, and other regions, that the x great commercial supply of the metal is obtained. It is not till the drifts get exhausted, or in districts where stream-work- ing is not remunerative, that the auriferous veins are attacked ; though, generally speaking, where the vein is a fair one, it forms the steadiest and most reliable source of supply. What are termed " gold ores" are not ores in the strict sense of the term ; for whether native amalgams or ores of other metals, the gold they contain, as may be seen by referring to the next section, is still in the free and uncombined metallic condition. According to the present state of our knowledge, the metal is always native, whether occurring in veins of quartz, calc-spar, and baryta, disseminated through the older schistose rocks, incorporated with other ores, or scattered abroad in drifts of sand and gravel.* While gold occurs notably in the drifts of the Urals, Brazils, California, Nevada, Colorado, British Columbia, Australia, and New Zealand, it is also found in minor quantities along the river-courses of many other regions India, Africa, the United States, and Southern Europe and very sparingly in our own islands, as in Wicklow, Devon, Wales, and the Scottish Highlands. It is mined in Brazil, Central America, Mexico, California, Australia, Spain, Hungary, Transylvania, the Urals, Altai Mountains, and in Sweden; but attempts at mining in Britain (Devon and Wales) have hitherto proved unremuner- ative. The metallurgical processes for the reduction and re- fining of gold lie beyond our province ; but whether by wash- ing and smelting, by amalgamation with mercury, by treatment with alkalies or other modes of liquation, some of them require considerable chemical skill and nicety of manipulation. The statistics of gold are very imperfect, and in most cases * With regard to the occurrence of gold, the following remarks by P. B. Smyth, Secretary of Mines for the Colony of Victoria, may be of use to the geological student : ' ' Gold is now found to occur not only in quartz-veins and the alluvial deposits derived from these and the surrounding rocks, but also in the claystone itself ; and, contrary to expectation, flat bands of auriferous quartz have been discovered in dykes of diorite, which intersect the upper Silurian or lower Devonian rocks. Quartz of extraordinary richness has been obtained from these bands, and the new experience of the miner is leading him to look for gold in places hitherto entirely neglected. It is probable that some time may be lost, and that his labours may not always be well directed or success- ful, but it is commendable that he should not be deterred from explorations by warnings and remonstrances founded on surmises often baseless. If he had already followed the older precepts, we should at this moment have been de- pendent- for our yield of gold on the shallower alluviums, and the surface only of the veins of quartz." 286 THE METALS AND METALLIC ORES. little better than guesswork. Not only does the quantity raised in any given locality vary from year to year, but new localities are unreported, and the success of mining adventures is often either kept secret, or exaggerated for speculative pur- poses. Roughly estimated, the total yield of the world may be set down at 460,000 Ib. troy, representing an approximate value of ^23,000,000. The uses and applications of gold in the arts and industries are innumerable. It is employed for coinage, for domestic and personal ornaments, for the formation of alloys, for the preparation of pigments, and for gilding of other metals, wood, plaster, and paper-hangings, and for the preparation of wire and leaf in all their multifarious applications. The extension of its use is generally the test of a nation's wealth, and year after year it is more and more employed in the fabrication of articles of luxury and ornament. Platinum. The metal Platinum or Plating discovered in 1741 in the mines of Peru, and so named by the Spaniards in allusion to its silvery colour -platina, the diminutive form of plata, silver is found only in a native or metallic state. What is termed " platinum ore," or crude platinum, is merely an admixture with other metals, such as palladium, rhodium, osmium, iridium, titanium, gold, silver, iron, and copper. Since its discovery in Peru it has been found in Brazil, California, the Urals, Borneo, and other countries. It is usually obtained from drifts in rounded grains or flattened pellets, of a metallic lustre and white colour. When pure it has very much the colour of silver, but of inferior lustre. It is the heaviest of known metals, its specific gravity after hammering being about 21.5. It is exceedingly ductile, malleable, tenacious, and diffi- cult of fusion, but capable of being welded at a high tempera- ture. It undergoes no change under the combined action of air and moisture, resists the strongest heat of a smith's forge, but can be melted by voltaic electricity, or by the oxy hydrogen blowpipe. It is not acted upon by any of the pure acids, but is dissolved by chlorine and nitro-muriatic acid, and is oxidised at a high temperature by pure potassa and lithia. A metal possessed of such properties is eminently fitted for chemical works and laboratories ; hence it is manufactured into crucibles, evaporating dishes, stills for concentrating sul- phuric acid, spoons, blowpipe-points, tongs, forceps, wire, and similar articles. It is also used for galvanic apparatus, orna- mental work in chains and trinkets, medals, and at one time by the Russian Government for coin. It forms alloys with NATIVE METALS. 287 indium, with iridium and rhodium, and with gold, which are said to possess properties of resistance superior to the pure metal ; and with equal parts of steel it constitutes the best white speculum-alloy known. According to Wagner, the amount of metallic platinum annually produced does not exceed three tons, and of this the greater portion comes from the Urals. Palladium. The metal Palladiiim (Pallas, the goddess), discovered by Wollaston in 1803, is usually found in very small grains, of a steel-grey colour and fibrous structure, in auriferous and pla- tiniferous sands. Its specific gravity is about 11.5; and in fusibility it stands intermediate between gold and platinum. When native it is alloyed with a little platinum and iridium, or with gold and silver, as in the Porpezite of Peru, which con- sists, according to Berzelius, of 85.98 gold, 9.85 palladium, and 4.17 silver. It is ductile as well as malleable, and is considerably harder than platinum. It is oxidised and dis- solved by nitric acid; but its proper solvent is nitro-hydro- chloric acid. It forms alloys, most of which are brittle, with arsenic, iron, bismuth, lead, tin, copper, silver, gold, and plati- num ; the alloy with nickel is ductile. It is sometimes used for the finely divided scales of mathematical and astronomical instruments; for the smaller chemical weights; and i per cent added to steel produces a smoother cutting edge. Silver. The early and well-known metal Silver is found native in the older rocks, in threads and strings, in arborescent moss-like aggregates, and in plates and nuggets often of considerable magnitude. In its native state it often occurs as an alloy with gold, platina, mercury, copper, or arsenic more frequently, perhaps, with mercury than with any other metal. Two speci- mens of " native silver " from Allemont, in Dauphine, yielded respectively to Mr Church's analysis 26.15 an( ^ I &34 of mercury. Being principally obtained from its ores, or from other ores with which it is in intimate union, its nature, pro- perties, and uses will be better considered under the section, " Metallic Ores." Mercury, Copper, Iron, &c. The same may be said of Mercury, Copper, Arsenic, Anti- mony, and Bismuth, which, though occasionally found native, or as native alloys, yet occur in quantities too unimportant to affect their commercial values. The remark is still more appli- cable to Iron, Lead, Zinc, and Tin, which are all lessor more doubt- 288 THE METALS AND METALLIC ORES. fully native, and even when found only in fragments interest- ing to the mineral collector. With regard to native iron, it occurs in two states ist, meteoric iron, which has fallen from the heavens in stones and masses sometimes of considerable size, and contains nickel along with cobalt and traces of other metals ; and 2d, telluric iron, which occurs in minute grains and scales in other mineral veins, and contains carbon, or occasionally some other metal, but not nickel. It is some- times very difficult, however, to assign an origin to certain masses of iron as those, for example, discovered by Nordens- kiold in 1870 at Ovifak in Greenland. There, fifteen huge masses of native iron (one of them calculated at eighteen tons), were found within an area of 150 square feet, and apparently associated with a basaltic rock, which also con- tained many fragments of metallic iron. We say apparently associated, for these detached blocks were partially incrusted with basalt, and the whole evidently owed a common origin. Nordenskiold and Wohler would assign to these masses an extra-terrestrial origin ; while Daubree and Berthelot are in- clined to regard them as products of fusion and eruption from below the enveloping basalt sometimes containing as much as twenty per cent of iron oxide. The following are the results of Daubree's examination : Iron, metallic, ..... Iron, combined with oxygen, sulphur, and phosphorus, Carbon, combined, Carbon, free, Nickel, Cobalt, Oxygen, Arsenic, sulphur, phosphorus, silica, copper, water, &c., 40.94 30-15 3.00 1.64 2.65 0.91 12.10 8.61 100.00 On the whole, the native metals, with the exception of gold, platinum, silver, and mercury, are of no great commercial im- portance ; and it is almost exclusively from the ores that we derive by ingenious and often difficult processes our main metallic supplies. IT. THE METALLIC ORES. As already stated, the great majority of the metals occur in nature, not as free and simple elements, but in combination with other substances, forming what are termed ores. These ores have all, more or less, a stony aspect; but in general their THE METALLIC ORES. 289 higher specific gravities, their more varied colours, and their metallic lustres, in the fresh fracture, serve generally to distinguish them from ordinary stones. Almost all of them occur in veins traversing the older rock-formations the clay-band and black- band ironstones, and the copper-slates of the stratified systems being the chief exceptions. They present numerous varieties, and are often very complex in composition their reduction to the metallic state requiring, in some instances, great chemical skill and expensive manipulation. Mineralogically, they are classed and treated as oxides, sulphides, carbonates, silicates, &c. ; and in many respects this arrangement, which has already been given in Chapter II., has much to recommend it. Occa- sionally they are arranged, according to their metallic bases, as ores of iron, ores of copper, and ores of lead; and these metals, again, treated according to their physical properties of weight, hardness, brittleness, ductility, malleability, and capability of being welded. In metallurgy, this plan has many advantages, as bringing each metal, with its several ores, dis- tinctly and directly under the eye of the inquirer. Indus- trially, it matters little what plan of arrangement is followed, so long as the geological sources and nature of the ores are described, the peculiarities of the metals explained, and their uses in the arts and manufactures briefly indicated. Adopting this view, we shall take the metals in alphabetical order, as sufficient for economic purposes, and as affording, perhaps, the readiest means of reference. It is true that some of them are unknown in the arts ; but even these, in the rapid progress of industry, may yet be utilised, and acquire a commercial value. And economically speaking, there are few substances on which more labour and capital are expended than on the ores and metals in the mining, the transport, and the reduc- tion of the former, and in the working, fashioning, and myriad applications of the latter. Metallurgy in all its branches is a gigantic art, whether as regards the science and ingenuity dis- played, the amount of labour and capital employed, or the value and importance of the substances produced. And gigantic as it seems, it is yearly on the increase, not merely in the amounts produced, but in the adoption of more skilful methods, by which production is cheapened and improved, and substances formerly thrown to the waste-heap utilised and in- vested with commercial importance. Aluminium. Aluminium, though never found in a free or native state, is extensively diffused in nature in the different compounds of T 2QO THE METALS AND METALLIC ORES. alumina. Commercially, it is obtained from cryolite and Bauxite the former a double fluoride of sodium and aluminium found in Greenland, and the latter a hydrous sesquioxide of iron and alumina occurring abundantly near Beaux in France. It is now principally manufactured in France, the works insti- tuted by Mr Isaac L. Bell at Washington in Durham having ceased to prepare it several years ago. As a metal it is silvery white, but less lustrous than silver ; has a specific gravity of only 2.56, and when hammered of 2.67 ; has a fusing-point between those of zinc and silver; is very tenacious; resists oxidation even in moist air : is dissolved only by hydrochloric acid ; conducts electricity eight times better than iron ; but is easily affected in its character by admixture with other metals. One of the most important of its alloys is aluminium bronze, consisting of 90 copper and 10 aluminium. This bronze is extremely hard, tenacious, and ductile, has the colour and bril- liancy of gold, and bars of it may be worked hot as easily as the best quality of steel. Both the pure metal and the bronze are possessed of many properties to recommend their use in the arts and manufactures lightness, toughness, and resist- ance to corroding agencies but somehow neither are manu- factured on a large scale, the demand being chiefly for trinkets and smaller articles of ornament. The ores of aluminium are abundant enough, but no process sufficiently cheap has yet been discovered for the elimination of the metal on a large scale. Antimony. Antimony as a metal is of a tin-white colour, with a greyish or yellowish tarnish ; somewhat sectile, but so brittle as to be easily reduced to powder by trituration ; fuses at- 900 ; and has a specific gravity of 6.712. It is sometimes found native as an alloy with silver, iron, and arsenic ; but it is obtained most abundantly from the sulphide or grey ore of antimony (stibnite), which consists of 74 antimony and 26 sulphur. This ore occurs in veins in the older crystalline and granitic rocks, and is found in Germany, Hungary, Spain, Borneo, Australia, and in Cornwall. Occasionally it is compact or mas- sive, but more frequently occurs in long, prismatic, fibrous-look- ing crystals, sectile and somewhat flexible, cleavable, and easily iusible. There are other ores of antimony, as Allemontite, or arsenical antimony ; Cervantite and Valentinite, or oxides often arising from the alteration of the sulphide ; and Kermesite, or red antimony, a compound of the sulphide and oxide ; but these are commercially unimportant. The ores of antimony are easily reduced to the metallic state, and the metal is chiefly employed in making the alloys called type-metal (6 lead, 2 anti- THE METALLIC ORES. 29 1 moiiy), stereotype-metal (6 lead, i antimony), music-plates, and Britannia metal, which are variable compounds of lead, tin, and antimony. It is used also in anti-friction composi- tions, in the production of "iron black/' and some of its pre- parations are employed in medicine, in the production of orange and yellow pigments, and in the " blue fire " of the pyrotechnist. Our supply of antimony about 2000 tons a- year is wholly imported, none of its ores being at present mined in the British Islands. Arsenic. Arsenic (Gr. arsenikon, masculine), so called from its pos- sessing strong or powerful properties, occurs chiefly in veins in the crystalline and transition strata, along with ores of anti- mony, silver, and lead ; and the purest specimens usually con- tain traces of antimony, iron, silver, or gold. The native metal is generally found in granular irregular masses or dis- seminated ; is brittle ; has a whitish lead-grey colour when newly broken ; but soon tarnishes on exposure to the atmo- sphere, and becomes coated with a black sub-oxide of the metal. When struck or heated, it gives off a strong garlicky smell, known as the "arsenical odour;" and on being pulver- ised and moistened, it undergoes spontaneous combustion. It has a strong tendency to combine with other metals ; hence such natural compounds as arsenic-silver, arsenic-antimony, arsenic-glance, &c. It is found in France, Germany, Bohemia, Transylvania, Norway, United States, and other regions, and usually in combination with other metals. Its more abundant ores are arsenical antimony (63.62 arsenic, 36.38 antimony); white arsenic, or arsenolite (65.76 arsenic, 24.24 oxygen); realgar, or red arsenic (70.09 arsenic, 29.81 sulphur); and orpiment, or the yellow sulphide (61 arsenic, 39 sulphur). Both realgar and orpiment are artificially prepared as pigments, as noticed in Chap. XIII. The metallic arsenic of commerce is chiefly obtained from mispickel, or arsenical iron pyrites. It is used in small quanti- ties in the preparation of several alloys ; in the manufacture of opal-glass ; in the making of shot, to which it imparts a cer- tain degree of hardness ; in pyrotechny and signalling, as a brilliant white light ; in various pharmaceutical preparations j in the production of realgar, the red proto-sulphuret, and of orpiment, the yellow sesqui-sulphuret, or king's yellow; and the well-known pigment, Scheele's green, is an arsenite of copper. The metal and all its compounds are violent poisons. According to the returns received by the Mining Record Office in the year 1872, the amount of arsenic produced in the United 2Q2 THE METALS AND METALLIC ORES. Kingdom (Devon and Cornwall) was 5172 tons, valued at Barium. Barium (Gr. barys, heavy), or the metallic basis of the earth baryta, was discovered by Sir H. Davy in 1808, by the voltaic decomposition of the moistened carbonate of baryta in contact with mercury. It occurs in nature only as an oxide baryta ; and of this there are two well-known varieties, the carbonate and sulphate, whose characters and uses have been described in Chap. XIII. Like sodium and potassium, barium is known only to the chemist. It is of a whitish-grey colour, has little lustre, and on exposure to the air or water becomes rapidly converted into its oxide. In 1872 there were prepared in Cornwall 65 tons chloride of barium, the estimated value of which was Bismuth. The metal Bismuth occurs in various states and combina- tions. Its colour is silver-white, with a slightly reddish tinge ; it is very sectile ; brittle when cold, but somewhat malleable when heated; and readily fusible, even in the flame of a candle. Its specific gravity is 9.727; hardness from 2 to 2.5; and fusing-point, 476 Fahr. It occurs native, associated with the ores of silver, cobalt, and tin, in veins traversing the older crystalline strata. It is found also as an oxide under the name of bismuth ochre; as a sulphuret called bismuthine (81.6 bis- muth, 18.4 sulphur); as a sulphuret with copper, cupreous bismuth or tannenite (62 bismuth, 19 sulphur, 19 copper); as a sulphuret with copper and lead, Aikinite or needle-ore; and in several other less important combinations. It is found in the mines of Cornwall and Cumberland; but the principal com- mercial supply, which is said not to exceed 20 tons a-year, is obtained from Schneeberg in Saxony, from South America, and from South Australia. In 1872, the amount produced in Bri- tain did not exceed two tons. From its fusibility it is easily reduced; but the demand for the metal is limited. The metallic bismuth of commerce is never quite pure, but con- tains from 3 to 5 per cent of other ingredients, as copper, sulphur, antimony, and arsenic. Bismuth is chiefly employed in the formation of alloys with other metals with tin, which it renders more elastic and sonorous; with tin and lead to form soft solder, cliches for stereotype, and cake-moulds for toilet-soaps ; and with tin and lead, in the proportion of 8 bismuth, 5 lead, and 3 tin, to form THE METALLIC ORES. 293 fusible metal, which melts at 200, and is useful in taking casts and other impressions.* It is also used in medicine, in the preparation of pearl-powder ; and the nitrate, mixed with a solu- tion of tin and tartar, has been employed as a mordant in calico-printing. Preparations of the oxide enter into the com- position of some kinds of glass, and are also employed in por- celain-painting and glass-staining. Cadmium. Cadmium is rather a rare metal, and is found chiefly in con- nection with the ores of zinc, the Silesian native oxide of zinc containing from i ^ to 1 1 per cent of cadmium ; that of the United States usually from 3 to 4. It was discovered by Stronmeyer and Herman in 1817, and received its name from its association with zinc, the cadmia fossilis of the older min- eralogists. As a metal, it is of the colour and lustre of tin; soft, sectile, and ductile; but rather harder and more tenacious than tin. Its specific gravity is about 8.6 ; its melting-point considerably under redness ; and when heated in the atmo- sphere it readily takes fire, and burns with a brownish-yellow inodorous smoke. It forms alloys with other metals, but its rarity not more than 20 or 25 cwts. (2839 Ib. in 1872) being annually prepared in Europe prevents its use in the arts. Its price is about 55. per Ib. The iodide and bromide are occasionally employed in photography; the sulphuret is used as a yellow pigment and in pyrotechny ; and mixed with lead, tin, and bismuth, cadmium forms a fusible metal (Wood's alloy), occasionally employed for stopping teeth. This alloy, which melts at 158, consists of 15 bismuth, 8 lead, 4 tin, and 3 cadmium. Caesium. The chloride of Ctesium, one of the alkali metals, was dis- covered in 1860 by Bunsen and Kirchoffin the mother-liquor of certain of the saline springs of Germany, and so named from the two blue lines (Lat, casius, sky-blue) of its peculiar spectrum. It belongs to the same group of elements as lithium, sodium, potassium, and rubidium, and occurs in the waters of Durckheim, Kruznach, Vichy, Baden-Baden, and other springs, * As bismuth enters to a greater or less extent into all the soft solders and fusible metals, the composition and melting-points of a few of these alloys may be given : 8 parts bismuth, 5 lead, 3 tin, . . . . 212 Fahr. 2 ii ii I M I il .... 201 n 5 H 3 ,i 2 , 199 n 15 n n 8 M 4 M 3 cadmium, 158 u 2Q4 THE METALS AND METALLIC ORES. as well as in lepidolite, lithia-mica, carnallite, and other min- erals. It is always found in company with rubidium, and, though its compounds are pretty numerous, has never been obtained in the pure metallic state. Calcium. Calcium, the metallic basis of lime, was first discovered by Sir Humphry Davy, in 1808, by the electric process. It is a substance of a brilliant pale yellow ; sectile, ductile, and mal- leable; has a specific gravity of 1.578; is oxidised on ex- posure to air ; and rapidly decomposes water. It is unknown in the industrial arts and manufactures, and, indeed, is only occasionally seen in the chemical laboratory ; but its com- pounds the carbonate, sulphate, fluoride, phosphate, and silicate are among the most abundant of natural products, forming the various limestones, gypsums, fluor-spars, apatites, and cherts of the geologist. Cerium. Cerium is another of those metallic substances known only to the scientific chemist. It was discovered in 1803, simul- taneously by Klaproth, and by Kissinger and Berzelius. It exists, together with lanthanium and didymium, in cerite, allanite, orthite, and a few other rare minerals, and appears as a greyish-brown infusible powder, which assumes a metallic lustre by friction. Chromium. Chromium, discovered by Vauquelin in 1797, is known to the chemist as a hard, brittle, and greyish powder, having a decided metallic lustre. Of itself, it has received no industrial application ; but several of its compounds are extensively used as brilliant and durable colouring materials. It is found in chrome-ochre (sesquioxide), in chromate of iron or chromite (sesquioxide combined with protoxide of iron), in chromate of lead or crocoisite, in some iron ores, and as the colouring prin- ciple of many minerals emerald, serpentine, olivine, &c. Its most abundant ore is the chromate of iron found in various parts of Germany, France, the Urals, Norway, United States, Scotland, and the Shetland Islands. According to Von Kobell, a Norwegian specimen consisted of sesquioxide of chromium, 54.08 ; protoxide of iron, 25.66 ; alumina, 9.02 ; magnesia, 5.36 ; and silica, 4.83. By treatment of this ore are obtained the chromates of potash, the beautiful yellow chromate, and the red bichromate ; and from these again are prepared chro- THE METALLIC ORES. 295 mic acid, the green oxide of chromium, the blue oxide of chro- mium, chromate of lead, and other salts so largely employed in dyeing, calico-printing, and the colouring of glass and por- celain. The chrome colours, whether yellow, orange, red, green, or blue, are amongst the most brilliant and beautiful we possess, and entitled to be ranked among the most successful achievements of modern chemistry. Cobalt. As a metal, Cobalt is not of itself employed in any of the in- dustrial arts ; but its oxide (prepared by nickel refiners) is ex- tensively used in imparting a fine rich blue to glass, and in the glazing and painting of porcelain and stone-ware. Metallic cobalt exhibits a steel-grey colour with a reddish tinge, is sus- ceptible of a brilliant polish, is malleable and ductile, tougher than iron, and requires a very high temperature for its fusion. Its principal ores are arsenical cobalt, consisting of cobalt, arsenic, iron, and nickel ; and grey cobalt, containing cobalt, arsenic, iron, sulphur, and nickel. These ores occur in Sweden, Ger- many, Cumberland, and Cornwall, in veins associated with other ores. They are picked, ground, and roasted in reverberatory furnaces, after which they undergo various chemical treatments and admixtures to produce what are termed zaffre, and smalt, or azure-blue. This azure-blue, which is essentially a glass of cobalt, silicious sand, and potash, is ultimately reduced to powder, and becomes the fine blue pigment, or "cobalt-blue " of commerce. What are known as cobalt-ultramarine, caerul- eum, cobalt-green, cobalt-yellow, cobalt-bronze, &c., are various colours and pigments obtained from cobalt and admixtures by ingenious chemical processes belonging strictly to the do- main of technology. Germany is the great manufacturer of smalt upward of a thousand tons being annually prepared from her ores of cobalt. According to the returns received by the Mining Record Office in 1872, there was only one ton of cobalt raised in the United Kingdom value 20. Copper. Copper (Lat. cuprum, a corruption of Cyprium, from the island of Cyprus, whence it was originally brought), is one of the most abundant and earliest known metals having been the chief ingredient in bronze for domestic utensils and weapons of war, long before the discovery and reduction of iron. As a metal it is distinguished by its peculiar red (copper-red) colour ; has a hardness of from 2.5 to 3 ; specific gravity from 8.5 to 8.9; is malleable and ductile; less tenacious than iron, but more 296 THE METALS AND METALLIC ORES. than gold, silver, or platinum ; and requires a temperature of nearly 2000 Farm, or that of white heat, to fuse it. In dry air it remains untarnished ; but in a damp atmosphere is soon covered by a green rust or " verdigris." It is readily acted on by acids, which form with it green or blue salts of a poisonous nature ; hence the necessity of care in the employment of copper utensils for culinary and domestic purposes. It is easily detected in solutions by the bright blue produced by the ad- dition of liquid ammonia, by the brown precipitate formed by the ferro-cyanide of potassium, or by its speedily coating a slip of polished steel or iron (a penknife blade, for example) with a film of metallic copper. Copper occurs native in the metamorphic and igneous rocks in threads and strings and arborescent incrustations ; also in- vesting, massive, and disseminated, but rarely in loose grains or lumps. Occasionally it is found deposited in mines from water containing the sulphate, after the manner of the electro- type process ; and not unfrequently large anomalous masses weighing from 1600 to 6000 Ib. (like those of Lake Superior and South America) are found in the igneous rocks. Native copper is also found in Siberia, the Faroe Islands, Cornwall, the Kilbarchan hills, Brazil, Chili, and Peru the American specimens usually containing a small percentage of silver. More frequently and more abundantly it occurs as an ore in many formations the yellow copper ores (pyrites), the grey copper ores, and some of the copper salts being the more important and valuable. These ores, with the exception of the copper-slate of Germany, which is a stratified deposit, are found in veins generally traversing the older rock-systems Metamor- phic, Cambrian, and Silurian. The ores most frequently used by the metallurgist, are cuprite, or the red oxide (88.80 copper, 11.20 oxygen) ; mdaconite, the black oxide, resulting from the decomposition of other ores (from 90 to 98 copper); Redruthite (Redruth in Cornwall), the grey sulphide or vitreous copper (79.12 copper, 20.36 sulphur); chalcopyrite, or copper pyrites, a double sulphide of copper and iron (34 copper, 30 iron, 36 sulphur, &c.); erubescite, another double sulphide of copper and iron, so called from its iridescent or pavonine tints (60 copper, 14 iron, 25 sulphur, &c.); tetrahedrite, a double sulphide of copper and antimony, with zinc, iron, &c., (from 30 to 40 of copper) ; azurite, the blue carbonate (69 copper oxide, 25 carbonic acid, and water); malachite, the green carbonate (70 copper oxide, 21 carbonic acid, and water); chrysocolla, the hydrous silicate of copper, a mixed ore, usually containing about 40 copper oxide, 28 THE METALLIC ORES. 2Q/ silica, 24 water, with iron and alumina ; and atacamite, or the native oxychloride, from Chili and Peru. The salts of copper arsenides, phosphates, sulphates, &c. though extremely numerous, are of more interest to the mineralogist than to the metallurgist and economic geologist. The ores of copper, being of a mixed nature, require various processes of washing, smelting, and refining, to reduce them to the metallic state the resultant metal usually containing traces of other metals, as lead, iron, and antimony. In 1872, the copper ores raised within the United King- dom (chiefly in Cornwall, Devon, Cheshire, Anglesea, and Ireland), amounted to 91,983 tons, valued at ,443,738; and the metal obtained to 5703 tons, computed at ,583,232. During the same year there were imported into the United Kingdom 43,65 6 tons copper ore, 28,779 regulus, 731 old copper for remanufacture, and 47,669 unwrought and part wrought, besides copper manufactures to the value of ,71,278. Copper is extensively employed in the arts and industries of all civilised countries, either alone or as an alloy. Alone, it is used for boilers, pans, &c., in sugar-works, distilleries, breweries, &c. ; for domestic and culinary utensils ; for ship sheathing ; for telegraph and other wires ; and for a great variety of well-known purposes. As an alloy its employment is still more extensive and varied, whether as brass (two parts of copper to one of zinc); mosaic gold (65 copper, 35 zinc) ; Bath metal (78 copper, 22 zinc); pinchbeck (3 of copper and i of zinc) ; ancient bronze (from 4 to 15 of tin); gun-metal (91 copper, 9 tin); bell-metal (78 copper, 22 tin) ; gong-metal (80 copper, 20 tin) ; statuary bronze, varying proportions of copper, tin, zinc, and lead ; German silver, or argentane, an alloy of copper, nickel, and zinc, in varying proportions, according to the colour or hardness required ; or standard metal, an admix- ture of copper and manganese. The salts of copper (sulphates, oxides, &c.), are also largely used in the preparation of blue and green pigments, and some of them are likewise employed in medicine. Didymium. Didymium, one of the rarer metals, of whose properties little is yet known, was discovered by Mosander in 1841, and so called because found as twin-brother (Gr. didymos, twin) with lanthanum in the oxide of cerium. In the metallic state it appears as a grey lustrous powder ; its oxide is a dark-brown powder ; and its salts are of pinkish or amethystine hue. It has no commercial value, and few of its compounds have yet been examined. (( IJ^JVE^BITX f 298 THE METALS AND METALLIC ORES. Glucinum. Glucinum, the basis of the earth glucina, is another of the rarer metals, only known as yet to the scientific chemist. It is of a white silvery colour ; has a density of 2.1 ; has a melting- point below that of silver ; and, according to Debray, can be forged and rolled into sheets like gold. Its earth, glucina, was discovered by Vauquelin in 1798, constituting nearly 14 per cent of the beryl and emerald, which owe to it their fine green colour. It combines with all the acids, and forms with them sweetish salts j hence its name. Neither earth nor metal is used in the arts, though chemists anticipate that the former may probably be employed in the production of artificial gems. Gold. Gold, as mentioned in the preceding section, is found only in the metallic state, either pure and simple, or as an amal- gam with silver (electrum), with palladium (porpezite], and with rhodium. Even when it occurs as auriferous pyrites it is still in the native state, and not as a sulphide, for though invisible in the fresh ore, it becomes visible on the decomposition of the pyrites, as minute shining metallic particles. In the amalgams it rarely forms less than 70 per cent of the mass the remain- der being silver, palladium, or rhodium, with traces of iron and copper ; * and in the pyrites it occurs usually in small but very variable proportions. Whether disseminated in rocks or ap- pearing in veins, gold is always a native metal the iron pyrites, copper pyrites, arsenical pyrites, galena, and blende, with which it is incorporated, being mere accompaniments, like the quartz, calc-spar, and baryta, which usually constitute the matrix or veinstone. Indium. This metal, which was discovered in 1862 by Reid and Richter in the zinc-blende of Freiberg, and so named from the two indigo-coloured lines which characterise its spectrum, has hitherto been obtained in such small quantities as to pre- vent its thorough examination. It is of a lead-grey colour, soft, very malleable, and marks paper like lead. Its com- pounds impart a violet tint to the flame of a Bunsen's burner. Indium. Indium, one of the rare metals discovered by Dr Wollaston, Ife^f a greyish-white colour, brittle, very infusible, and has a * Two specimens of Scottish gold one from Wanlockhead, and another from Sutherlandshire yielded respectively to Mr Church's analysis 12.39 an d 20.71 per cent of silver. THE METALLIC ORES. 299 specific gravity of about 18.6. It occurs in nature in connec- tion with platinum, palladium, and osmium osmium-iridium, or " native alloy," being its most abundant form. It derives its name from the variety of hues (Gr. iris, a rainbow) which the mixture displays while dissolving in hydrochloric acid. It is the most infusible of the known metals, and is used chiefly in porcelain-painting to produce black and grey colours. It is also used for the nibs of gold pens, and is said to be worth 24 an ounce. It forms alloys with copper, gold, mercury, and platinum that with the latter being malleable and capable of being worked and less easily attacked by chemical reagents than pure platinum. Iron. Iron, of all the metals the most useful, is likewise the most abundantly diffused in nature. It is found, though sparingly, as a native alloy; occurs as an ore in rocks of all ages, and in every country is met with in most mineral springs ; and appears in the tissues and fluids of many plants and animals. Though readily tarnished, rusted, or oxidised by exposure to air and moisture, metallic iron has in the fresh fracture a peculiar grey colour known as " iron-grey" or " steel-grey," and when polished possesses much lustre. It is not very malleable, but extremely ductile and very tenacious. At common temperatures it is hard and unyielding, but at a red heat it is soft and pliable, and at a high red heat two pieces can be inseparably united by hammering or welded into one mass. It is very difficult of fusion, requiring for that purpose the highest heat of the blast- furnace. In this state it can be run into moulds, and is then known as cast-iron, which is hard, brittle, and of a granular texture. Subjected to repeated heating and hammering (puddling, as it is termed) it becomes less fusible, assumes a fibrous texture, gets tough and malleable, and is then known as forged or wrought iron. The average specific gravity of cast- iron is 7.27; that of forged, 7.78. Iron is attracted by the magnet, and is of itself susceptible of being rendered- mag- netic a property possessed by no other metal except nickel. Most of the iron of commerce contains variable quantities of carbon, silicon, sulphur, and phosphorus impurities which deteriorate its quality ; hence the scientific efforts of the iron- founder to reduce these to a minimum. Iron is capable of forming alloys with several of the metals, though in this state little used ; and with a small proportion of combined carbon it forms steel* a substance which, from its hardness, strength, * " Those varieties of iron," says Phillips in his 'Elements of Metallurgy,' "in 300 THE METALS AND METALLIC ORES. and susceptibility of receiving a fine cutting-edge, is of incal- culable importance to all the industrial arts and manufac- tures. As mentioned in the preceding section, native iron is a very rare and in some instances doubtful ' substance ; and all the iron of commerce is derived from ores (oxides, carbonates, &c.), either pure or in combination with various earthy ingredients forming ironstones. These~Qes- and ironstones occur in rocks of all ages the ores chjj&ffyrjn veins and abnormal masses among the older rocks, and-tfce ironstones in layers and nod- ular bands among, the strata of the carboniferous, liassic, oolitic, and other later systems. As metal-producers, these ores and ironstones are usually regarded under two sections ist, the SPARRY IRON ORES, the most important member of which is siderite, spathose iron, or carbonate of iron, and which include the day ironstones or " clay-bands " and "black-bands" of the coal and other stratified formations; and, 2d, the OXIDISED IRON ORES, embracing such well-known species as magnetite or magnetic iron, hematite or specular iron, and limonite or brown iron ore. The former section require roast- ing or calcination before being smelted, and are regarded as ores of easy reduction ; the latter go direct to the furnace, and are considered of difficult reduction. Besides these ores, iron is found in many chemical combinations, as chromates, phos- phates, sulphates, and sulphides, which are of great value in the arts, though not used for the production of the metal. Its presence in water is readily detected by the tincture of galls, or by ferro-cyanide of potassium the former turning weak solutions purple or dark-blue, and forming a black precipitate where the metal is more abundant; the latter producing Prussian-blue under similar circumstances. The following ores may be noticed as of chief commercial importance : Magnetite, Magneticlron, ox Black Oxide of Iron, is a rich and valuable ore, consisting, when pure, of 72.40 iron and 27.40 oxygen, or 69 iron peroxide, and 31 iron protoxide. It occurs chiefly in the igneous and metamorphic rocks, either in distinct octahedral crystals disseminated through the mass, or more which the amount of carbon is below the minimum of that contained in cast- iron, and above the maximum of that present in wrought-iron, are known as steel. The distinguishing peculiarity of this substance is its property of becoming hardened by rapid cooling, and softened by being slowly cooled. Steel being in its composition intermediate between cast and wrought iron, is fusible like the one and malleable like the other ; but requires a higher tem- perature for its fusion than cast-iron, and does not draw so readily under the hammer as wrought-iron. Steels in which the proportion of carbon is large, are known as strong steels, and are harder and more easily fusible than mild steels, in which the amount of that substance is less considerable." THE METALLIC ORES. 30 1 frequently in beds and masses of a granular brittle texture, and very rarely in veins. It is found in Sweden, Norway, Russia, Germany, Elba, and Spain, in Europe ; in Siberia ; and in North America the celebrated " Codorus ore" or "steel-ore" of Pennsylvania. From its bedded position it is often worked, as at Dannemora in Sweden, in open quarry ; and though difficult of fusion, is an esteemed ore, especially for the manufacture of steel and certain makes of iron. The impurities most frequently present in magnetite are pyrites, alumina, magnesia, and phos- phate of lime. Hcematite, or Red Oxide of Iron, is a still more abundant ore, occurring in rocks of all ages, sometimes in veins and some- times in nests or amorphous masses, as in the Furness and Whitehaven districts. It appears in several well-known varie- ties, as kidney-ore, in reniform masses, having a radiated crystal- line texture, as compact when void of the crystalline texture, as red-ochre or argillaceous haematite when soft and clayey, as specular iron when in crystals of a dark steel-grey colour, and as micaceous iron when foliated, with a soft unctuous feel. Its distribution is world-wide Scandinavia, Saxony, Elba, Cornwall and Devon, North Lancashire, and West Cumber- land, being the most important European localities. It pro- duces an excellent iron, 69 per cent being not unusual in pure varieties. Limonite, or the Brown Oxide of Iron, is another valuable ore, occurring in several varieties brown ironstone, pea-iron, bog-iron, and yellow-ochre all hydrous oxides, varying alike in mineral aspect and yield of iron, and arising in most instances from the decomposition of other ores. As its name indicates (Gr. leimo, meadow), it is frequently found as a deposit in bogs and marshes, and occurs also in bands and nodules in the secondary and later formations. From its origin, it contains more impurities than magnetite or haematite, and is said to be better fitted for castings than for wrought-iron. Ilmenite, Menaccanite, or Titaniferous Iron, is another import- ant ore, consisting of ferric and ferrous oxides, titanic oxide, and magnesia, in varying proportions. A specimen from Menaccan yielded to V. Kobell 42.57 Ti, 23.21 Fe, 29.27 Fe, 1.22 Mg, and 50 Ca. Titaniferous iron-ore is widely distributed; Norway, Sweden, the Ilmen mountains (hence the name), Canada, United States, Mexico, France, and Men- accan in Cornwall (hence the name), being well-known pro- ductive districts. It occurs also as titanic iron-sand, or ise- rine, in several countries, in which form it is said to produce a very hard and tough variety of iron. (See Titanium.) 302 THE METALS AND METALLIC ORES. Siderite, Spathose Iron, or Carbonate of Iron, is one of the most important sources of the metal, whether found in veins and stratiform masses in the old gneisses and clay-slates, or in beds in the coal, lias, oolite, and later formations. It occurs in crystallised, concretionary, granular, oolitic, and earthy varieties, all differing widely in mineral composition and value. The clay ironstones of the coal-formation appear in earthy bands and nodules (clay-bands), or in beds, mingled with coaly or bituminous matter sufficient for its own calcination (black-bands) ; while those of the lias, oolite, and later forma- tions are found in shelly bands, clayey bands, and nodules or septaria. Productive ores are worked in the old rocks of Germany ; in the coal-fields of France and Britain ; in the lias and oolite of England, and at one time in the Wealden. The amount of metallic iron may range from 20 to 50 per cent ; but ores yielding less than 28 are seldom regarded as of com- mercial importance. Franklinite (from Franklin county, New Jersey), is a com- pound ore, which has recently risen into great commercial im- portance. An average of several analyses by Rammelsberg gives 45.16 iron, 9.38 manganese, 20.30 zinc, and 25.16 oxygen. The ore occurs in metamorphic limestone of Silurian age, form- ing a bed from 20 to 30 feet thick, which is overlaid by 6 or 8 feet of red zinc ore. Both minerals are first treated for zinc, and the residues afterwards smelted for spiegeleisen. All iron ores containing manganese are found to produce excellent iron for the manufacture of steel. (See Manganese.) Iron Pyrites, so universally distributed, " is never directly treated" (we quote Phillips's 'Metallurgy') "for the sake of the iron it contains, but is frequently employed as a source of sulphur in manufactures of alum and sulphuric acid. When heated in the burners attached to sulphuric acid chambers, good pyrites yield about 46 per cent of sulphur, which is burned and oxidised in the usual way ; but the sulphuric acid thus obtained always contains traces of arsenic. Iron pyrites frequently contains small quantities of gold and silver, but these are seldom present in sufficient proportion to allow of their being profitably ex- tracted. Very large quantities of cupreous iron pyrites are now annually imported into this country from Spain and Portugal, and after being burnt for the manufacture of sul- phuric acid, the ' cinders ' are treated for copper by a process of wet extraction. The ferruginous residues (' Blue Billy') thus finally obtained yield on an average 96 percent of ferric oxide, and are extensively employed, both in the blast-furnace and for * fettling ' puddling-furnaces. By far the largest portion of that THE METALLIC ORES. 303 produced, amounting to several hundred thousand tons annu- ally, is used for tlje latter purpose." The amount of iron pyrites or sulphur ores raised within the United Kingdom in 1872, exceeded 65,916 tons, the computed value of which was ^39,470- There are other ores yielding iron, but the preceding are the most important and abundant, and are those usually reduced in Britain. In 1872, the iron ores raised in the United Kingdom amounted to 16,584,857 tons, valued at ,7,774,874 ; and the pig-iron produced 6,741,929 tons, worth ^"18,540,804. The following table, from Hunt's ' Mineral Statistics,' shows the districts from which the ores were obtained, the nature of ore, and their respective amounts and estimated values : District. Description of Ore. Tons. Value. Cornwall, . . R. and B. haematite, 48, 199 j 2 7,033 Devon, . B. haem. and magnetite, . 26,361 15.524 Somerset, . Brown haematite, 30,913 30, 163 Gloucester, Hydrated oxide, 199.453 i49,=;88 Wilts, . . Hydrated oxide, 96,117 36,168 Oxfordshire, Brown haematite, . . 6 3.536 47.652 Northampton Hydrated oxide, . '*'-' 1,004,093 377.736 Lincoln, Hydrated oxide, . :^{ 318,802 79.675 Shropshire, Argillaceous carbonate, . 408,425 153.669 Stafford, N., Hydr. ox. and argillaceous, 361,603 216,961 s., Argillaceous carbonate, . . 641,950 420, 135 Warwick, . Argillaceous carbonate, -. 43.375 16,246 Derbyshire, Argillaceous carbonate, . 307.183 184,308 Lancashire, Red haematite, . . 852,064 1,063,186 Cumberland, Red haematite, . . ' 9 * 7.45 2 1,141,416 York, N. Riding ,, W. Riding, Argillaceous carbonate, . Argillaceous carbonate, . 4,974,950 466,305 1,863,081 171,864 Durham and Nor- thumberland, . Argillaceous carbonate, . 97.953 36,730 North Wales, . B. haem. argill. carbonate, -* 27,775 19,710 South Wales and Monmouthshire, B. hasm. argill. carbonate, 1,247,594 744,465 Isle of Man, . . Spathose ore, . 994 497 Scotland, . . . Ireland, . . . Argill. and black-band, . B. haem. pea-ore and B.-band 3,270,000 176,550 817,500 158,562 Total iron ore, . .. J 5. 584, 357 ,7,774,874 " Burnt ore" from cup. pyrites, . . 252,239- Iron ore imoorted. .... 801,503 Total .... 16,638,599 During the same year (1872) there were imported into the United Kingdom 304 THE METALS AND METALLIC ORES. Tons. Value. Iron in bars, unwrought, , . . 82,888 ^"918,808 Steel, unwrought, 39,602 1,170,201 Iron or steel, wrought or unwrought, . 7,557 109,494 Total, .... 130,047 ,2,198,503 The uses of iron and steel in the arts and manufactures are so universal and miscellaneous as to render any enumera- tion impossible. In various forms, as tools, implements, in- struments, utensils, and machines, these metals appear in our agriculture, our architecture, shipbuilding, national defence, railways, telegraphs, engineering, spinning, weaving, baking, brewing, tanning, printing, dyeing, household furnishings and implements, and, in fine, through all the industries domestic and national that are characteristic of civilised existence. Before the current century they were little used in agriculture, architecture, or shipbuilding ; and then our railways, tele- graphs, and gigantic spinning and weaving factories were un- known. But now they enter into every art and manufacture, and year after year witnesses new extensions and new adap- tations of their employment. Nor is it alone in the metallic state that iron is so universally useful ; its chemical prepara- tions are likewise of value as pigments, dyes, and mordants, and some of them have been long and favourably known in medicine. Lanthanum. Lanthanum, or Lanthanium, is one of the rare metals dis- covered by Mosander in 1841, associated with didymium in the oxide of cerium, and so called from its properties being concealed, as it were (Gr. lanthano, I conceal), by those of cerium. Like its associate didymium, it is as yet known only to the scientific chemist as a soft, dark, lead-grey, metallic powder. Lead. Lead and its ores, mineralogically as well as commercially speaking, are of great interest and importance. As a metal it has been long and widely known ; is of a bluish-grey colour, soft, flexible, and inelastic ; and though ductile and malleable, yet possessed of very little tenacity. Its specific gravity varies from 11.3 to 11.4; its usual hardness is 1.5, and it fuses at a temperature of about 600 Fahr. In close vessels it does not appear to be volatile at a white heat; but melted in open vessels, it soon oxidises and passes into a grey powder, which, upon further exposure to heat and air, becomes yellow, and THE METALLIC ORES. 305 forms massicot, or protoxide of lead. " Pure lead," says Dr Ure, " is not affected by perfectly pure water free from air ; but if air be present, the metal is oxidised at its expense, and the oxide thus formed, combining with carbonic acid, is de- posited on the lead in minute crystals as a basic carbonate of lead. The water will then be found to contain lead in solu- tion, and such waters drawn from impure cisterns often pro- duce very distressing consequences. If the water contains any sulphates, the lead is thrown as a sulphate of lead, which is insoluble." Lead, as noticed in the preceding section, is rarely found native, and that chiefly in volcanic rocks, where it appears to be a product of fusion. Commercially, it is wholly obtained from the ores, and these occur in rocks and formations of all ages almost always in veins with various spars, as in the metamorphic schists and carboniferous limestones of our own country. Mineralogically, the ores of lead are numerous, and of great interest from their compositions and transformations ; commercially, comparatively few are used for the extraction of the metal. The chief ore is galena, lead-glance, or sulphide of lead, which occurs in veins in the metamorphic schists of the Highlands ; in the Cambrian and Silurian slate-rocks of Corn- wall, Devon, and Wales; and in the mountain limestones of the Mendips, Derbyshire, Yorkshire, Cumberland, Northum- berland, and Durham. It is found abundantly in almost every country France, Spain, Germany, Sweden, North and South America; and usually consists of from 85 to 87 lead, from 13 to 14 sulphur, with traces of iron- and other impurities, and not unfrequently an available percentage (2 to 5) of silver. As a mineral it belongs to the cubic system, has a specific gravity of 7.75, is of a lead-grey colour, and exhibits a strong metallic lustre. Other ores of lead of more or less importance are Bour- nonite, or antimonial lead ore ; cerussite, or carbonate of lead ; pyromorphite, phosphate of oxide of lead ; mimetesite, arseniate of oxide of lead; Anglesite, sulphate of lead; Cromfordite, chloride of lead; and molybdate of lead. The rarer ores (chromates, tungstates, vanadiates, &c.) are interesting only to the mineralogist, not to the metallurgist. According to the returns received by the Mining Record Office in 1872, there were 455 lead-mines in Britain, which yielded 83,968 tons of ore the estimated value being ;i, 146,155. The metal ob- tained amounted to 60,455 tons, computed at ;i, 209,115; while during the same year we imported 14,560 tons of lead ore, 69,841 of pig and sheet lead, and 441 of lead manufactures. U 306 THE METALS AND METALLIC ORES. The metal obtained from the ore, by roasting or by preci- pitation, is largely used in the arts and manufactures, partly in the pure state, partly as an alloy, and partly in numerous pre- parations. As lead it is used variously in architecture, for roofing, roans, &c. ; in chemical works, for pans, cisterns, linings for sulphuric acid chambers, &c. ; for gas and water pipes; for gun-shot, and numerous other purposes. As an alloy with tin, with bismuth, and with antimony, it is employed in the preparation of soft solder, white metal for domestic utensils, organ-pipes, type and stereotype metal, ships' nails, lining for tea-chests, and kindred uses too multifarious to men- tion. The preparations from the metal are also exceedingly numerous red-lead, white-lead, yellow-lead, litharge, acetate of lead, &c., used variously as pigments, in porcelain-painting, glass-making, dyeing, calico-printing, and in medicine. Lithium. Lithium, the metallic basis of lithia, is another of those rare substances known chiefly to scientific chemists. Lithia occurs in petalite, amblygonite, lepidolite, tourmaline, and other minerals ; is found in many mineral waters (see Chap. XV.), and has been detected in the ashes of certain plants. The metal has a silvery colour, but quickly tarnishes on exposure to air ; is softer than lead, but harder than potassium or sodium ; is sectile and somewhat ductile ; and is the lightest of all known solids, its specific gravity being only 0.589. It is much less oxidable than sodium or potassium; melts at 186; ignites at a light temperature, and burns quietly with an intense white light. When thrown on water it oxidises, but does not burn like sodium. As a metal it is unknown in the arts, but its oxide and some of its compounds are employed in medicine. Magnesium. Magnesium, the metallic basis of magnesia, is another silvery- looking metal, obtainable in any quantity from such an abund- ant earth, though only produced on a small scale owing to its limited commercial applications. It was first obtained by Davy, but recently in larger quantities by other chemists. Like aluminium, it is prepared by several chemical processes, and when pure is ductile and malleable, has a specific gravity of 1.75 and hardness of 3, fuses about the same temperature as zinc (770), burns in the air with a bright white light, arid in oxygen with intense and dazzling brilliancy. It has been employed for signalling, and in the production of light for instantaneous photography. THE METALLIC ORES. 307 Manganese. Manganese, originally discovered by Gahn, is a hard, brittle, greyish-white metal, somewhat resembling iron ; has a specific gravity of 8 ; is fused with great difficulty, but is readily oxidised. As an oxide it is abundant in the mineral kingdom, and traces of it have been found in the ashes of plants and in mineral waters. The ores of manganese are numerous, and often occur associated with those of other metals in the older rocks. The better known and more abundant are manganite t or the grey oxide ; wad, or the earthy protoxide ; cupreous man- ganese ; pyrolusite, or the black peroxide ; psilomelane, a com- pound of the oxide and baryta; Hausmannite, a peroxide occurring with other ores of the metal ; and Braunite, a bin- oxide in combination with iron peroxide, silica, and magnesia. The ores of manganese are largely used in the arts in glass-making, in pottery painting and glazing, in glass-staining and enamel, in the production of oxygen, chlorine, and chloride of lime, and as an admixture for improving the make of iron and steel. The celebrated spiegeleisen of Germany is such an admixture, and is either produced by artificial admixture, or by the use of iron ores (like Franklinite) containing manganese. It also appears, from recent experiments, that manganese can be substituted for nickel in the manufacture of German silver, without affecting the appearance or general character of the alloy. In 1872, the ores of manganese raised within the United Kingdom (chiefly in Devonshire) amounted to 7773 tons, having a value of .38,865. Mercury. Mercury, so well known in the arts and manufactures, is in many respects a peculiar and anomalous metal. At tempera- tures higher than 39 it is always fluid ; and hence, from its mobility and silvery lustre, is usually called " quicksilver." At temperatures below 40 it becomes solid, and has a specific gravity of 15.6 ; when fluid its gravity is only 13.5 ; under the blowpipe it is altogether volatile, or leaves a slight residuum of silver. It occurs in rocks of all ages, but is rarely found in a state of native purity, in which condition it is interspersed through the matrix in small shining globules. Its more abun- dant ores are cinnabar, or bisulphuret of mercury (86.29 mer- cury, 13.71 sulphur); native amalgam, an ore containing 36 silver and 64 mercury ; and calomel, or chloride of mercury (84.9 mercury and 15.1 chlorine). Cinnabar is the chief ore of commerce, and frequently occurs associated with iron pyrites :- - 308 THE METALS AND METALLIC ORES. in a matrix of quartz, calc-spar, or spathic iron ore. It is found in 'Spain, various parts of Germany and Hungary, the Urals, China, Japan, Borneo, Mexico, Peru, and abundantly in Cali- fornia. The annual production of mercury is said to be up- wards of 4000 tons, of which California yields nearly two-thirds, and Spain one-third. The best known mercury-mines in Europe are Almaden in Spain, and Idria in Carniola. At Almaden the mercury is said not to form veins, but to have impregnated the vertical strata of quartzose sandstone associated with carbona- ceous slates ; in the Asturias the mines are worked in car- boniferous strata ; and in Carniola it is disseminated in beds of grit, bituminous shale, or compact limestone of more recent formation. The industrial applications of mercury and its compounds are exceedingly numerous. The metal is used in the construc- tion of many scientific instruments thermometers, barometers, steam-gauges, &c. ; in the preparation of amalgams with other metals from its property of ready combination ; in the extrac- tion of gold and silver from their ores ; in silverising mirrors and reflectors ; in arming the cushions of electrical machines ; in the preparation of corrosive sublimate, mercuric-chloride, which is variously employed in preserving, dyeing, printing, etching, &c. ; in the manufacture of vermilion pigments ; in the preparation of the fulminate for percussion-caps, and other applications too numerous for detail. Molybdenum, Molybdenum, one of the rare metals, was discovered by Hjelm in 1782. It is of a whitish colour, brittle, very infusible, has a specific gravity of 8.625, and hardness of 8. It is obtained from molybdenite, or sulphide of molybdenum, an ore occurring in the granites and crystalline schists, in veins with tin and other ores, very much resembling the sulphide of lead, hence the name (Gr. molybdos, lead). It is also obtained from ivolfenite, or molybdate of lead. The sulphide is found in the metalliferous veins (magnetite and cassiterite especially) of Cornwall, Cumberland, Saxony, Scandinavia, and Greenland, and at numerous places in the United States of America. The metal is not industrially employed, but its sulphide is used in the preparation of a blue pigment for pottery-ware. Nickel. Pure Nickel has a silver- white colour with a slightly yellowish tinge, is ductile, malleable, hard, and easily polished, but very difficult of fusion. When quite pure it can be drawn into wire, \ THE METALLIC ORES. 309 rolled into sheets, hammered, and forged; has a tensile strength exceeding that of iron ; and hammered, its specific gravity is about 9. It is not altered by exposure to the air and moist- ure at ordinary temperatures, but is slowly oxidised at a red heat. It is found, as already stated, in all meteoric iron; but its principal ore is a copper-coloured mineral found in various parts of Germany, and called nickdine, or kupfer-nickel "nickel" being a term of detraction used by the miners, who expected from its colour that it would contain copper. Since the manufacture of German silver, or argentane, nickel has become an object of considerable importance, and is ex- tracted from several ores, as from Gcrfsdorffite, or nickel-glance, containing 35 per cent ; nickeline, or copper-nickel, 44 ; anti- monial nickel, 31 ; arsenical nickel, 29; Beudanskite, or silicate of nickel, 13 ; and from other sulphuretted ores of cobalt, iron, &c. These ores are found in many countries Germany, Russia, Sweden, Italy, Spain, Brazil, and the United States and are mostly difficult of reduction. As already mentioned, nickel is chiefly employed in the preparation of German silver, nickel-silver, or white metal, and similar alloys, consisting of variable proportions of copper, nickel, and zinc. Its salts are mostly of a grass-green colour, and the ammoniacal solution of its oxide of a deep blue. Within a very few years the price of nickel, according to Phillips's (' Elements of Metallurgy'), has risen from 43. to us. perlb.; and its present production, which is estimated at 600 tons annually, appears to be rapidly becom- ing unequal to the demand. Niobium, &c. Niobium, or Columlium, Pelopium, and Tantalum, are all very rare and closely associated metals indeed, the same metal derived by complex processes from the minerals known as Tantalates. These tantalates (of iron, manganese, tin, &c.) are found in the older granitoid and crystalline schists of Sweden, Greenland, Spain, and North America. The metals are known only to the scientific chemist, and have received their names, classical, geographical, and fanciful, in allusion to circumstances connected with their discovery or reduction. Osmium. Osmium was discovered by Smithson Tennant in crude plati- num, and so named from the strong disagreeable odour (Gr. osme, a smell) given out by its oxide. Two native alloys of osmium and iridium are known to mineralogists under the names of osmiridium and iridosmium, both of which are found 3IO THE METALS AND METALLIC ORES. in flattish grains or scales in the gold and platinum sands of the Urals and California. (See Iridium.) Potassium. Potassium, the metallic basis of potash, was discovered by Sir Humphry Davy, by the voltaic process, in 1809. It is a soft metal, can be cut like wax with a knife, has a white sil- very brilliancy in the newly cut surface, but quickly tarnishes on exposure. It is fluid at 120, is malleable at 50, with a specific gravity of 0.865, an d at 32 becomes brittle, with a crystalline texture. Its strong affinity for oxygen renders it difficult of preservation in a metallic state hence the neces- sity of keeping it in stoppered phials under naphtha. When heated in the air it takes fire and burns vividly with a violet light ; and when thrown on water decomposes it with violence the hydrogen and volatilised metal burning with a beautiful rose-red flame, while the oxygen combines to form potash. It is chiefly interesting to the geologist as being the base of an earth which enters so largely and multifariously into the composition of the rocky crust. Rhodium. Rhodium, one of the rare metals discovered by Wollaston in 1803, is usually associated with iridium, osmium, and palla- dium, in ores of platinum. It derives its name from the red colour (Gr. rhodon, a rose) of its solutions, though its own col- our is a whitish silvery-grey. It most resembles platinum in its character; is hard and very infusible, ductile, and mal- leable ; has a specific gravity of 1 2 ; and forms alloys with other metals. Its alloys with steel are extremely hard and tough, and take on a fine polish ; the metal itself is used for nibbing"gold pens* Rubidium. \ ; Rubidium, one of the alkali metals, was discovered by Kirchoff and Bunsen in 1 860 by the method of spectral analy- sis, and so named from the two red lines (Gr. rubidios, dark- red) of its spectrum. It is found in several of the German mineral waters, in lepidotite, petalite, lithia-mica, and other minerals, and in the ashes of many plants. As a metal it is obtained by intricate chemical processes, and is described by its discoverers as having a white colour with a tinge of yellow, and a silvery lustre. It has a specific gravity of 1.52 ; is as soft as wax even at 0.10; melts at 38.5; and is converted even below a red heat into a greenish-blue vapour. When THE METALLIC ORES. 311 exposed to the air, it instantly becomes covered with a bluish- grey film of sub-oxide, and takes fire in a few minutes, even more readily than potassium. When thrown on water, it takes fire with violent evolution of hydrogen, and burns with a flame exactly like potassium. Ruthenium. Ruthenium, another of the platinum metals, discovered by Glaus in 1846, is closely related in its characters to iridium, but of much less density, its specific gravity being only 11.4 instead of 18.6. It is extremely refractory, and unknown in the arts. Selenium. Selenium (Gr. selerie, the moon), so called from its colour and lustre, was discovered by Berzelius in 1817. It occurs asso- ciated with ores of tellurium, bismuth, gold, silver, copper, and iron pyrites. It is difficult of extraction ; has a specific gravity of 4.3 ; fuses at a temperature little more than that of boiling water ; and is known only to the scientific chemist. In its properties it is closely allied to sulphur, and is often asso- ciated with that element in the mineral kingdom. Silicium. Silicon or silicium, the base of silica, was discovered by Ber- zelius in 1823. It is a dark-brown powder, heavier then water, infusible before the blowpipe, non-volatile, and known only to the scientific chemist. Its oxide silica, the silicates, and silicious rocks and earths, constitute, however, a large portion of the ponderable crust (perhaps one-fourth), and are of ex- treme interest to the geologist. Silver. Silver, one of the early and well-known metals, is, when pure, of a peculiar white colour (silver-white), brilliant lustre, next in malleability and ductility to" gold, harder than gold, but softer than copper. Its specific gravity is from 10.5 to ii ; its melting-point about 1000 Fahr. ; and though unal- tered by air or moisture, it is readily tarnished or blackened by sulphuretted hydrogen. It resists the action of the caustic alkalies ; but is readily attacked by nitric and strong sulphuric acids, and by chlorine, iodine, and bromine. It occurs native in the older rocks, in threads and strings, in arborescent moss-like aggregates, and in plates and nuggets, often of considerable magnitude. In this state it is found at Konigsberg in Norway, in Germany, Peru, Mexico, and 312 THE METALS AND METALLIC ORES. in several parts of the United States New Jersey, Lakes Michigan and Superior. In its native state it is often found as an alloy with gold (electrum), with platinum, cop- per, arsenic, and antimony (dyscrasite) ; and from such com- pounds much of the silver of commerce is extracted. It is also largely obtained from ores, generally as a sulphide, and often in intimate union with ores of lead, antimony, bis- muth, &c. ; so that the ores yielding silver are, strictly speak- ing, ores of other metals. These ores are found chiefly in the older granitoid and crystalline schists, though argentiferous lead ores occur abundantly in secondary strata, as in the thick- bedded carboniferous limestones. The more important ores, commercially speaking, are argentite, or the vitreous sulphide, containing about 85 per cent of silver ; Stephanite, the brittle, grey, antimonial sulphide, containing about 65 of silver ; pyrargyrite, the red antimonial sulphide, 60 of silver; poly- basite, the cupreous sulphide, upwards of 60 of silver ; and cerargyrite, or the chloride (horn silver), containing 75 of silver. These and other ores are mined, crushed, picked, smelted, or amalgamated, for the production of the metal, the mode of treatment varying with the nature of the ore. The richest silver-yielding countries are Mexico, Nevada, Colorado, and Lake Superior, in N. America ; Chili, Bolivia, and Peru, in S. America ; and Norway, Hungary, Russia, Tran- sylvania, Saxony, and Spain, in Europe ; the total annual pro- duce of the world being estimated at 4,100,000 Ib. troy, of an approximate money value of ^13,000,000. There are no silver- mines proper in the United Kingdom, but in 1872 there were extracted from argentiferous lead ores 628,920 ounces, valued at ,157,230. As the lead smelted in 1872 amounted to 60,455 tons this would give upwards of 10 ounces to the ton of metal. The industrial applications of silver are numerous and im- portant. Being too soft when pure for general use, it is invari- ably alloyed with copper, whether for plate, for coin, or for ornamental purposes. It also forms alloys with lead, zinc, bismuth, tin, copper, and gold ; and such compounds under various names have numerous applications in the arts. It is extensively used for silvering other metals ; and some of its salts, like the nitrate, are largely employed in medicine, as marking-ink, and in photography. Sodium. Sodium, the metallic basis of soda, was discovered by Sir Humphry Davy, by the voltaic process, in 1807. As a THE METALLIC ORES. 313 metal it has a bright lustre, and a white silvery colour, with a tinge of red. It is soft, and readily moulded at 60, melts at 194, and rises in vapour at a red heat. It is lighter than water, its specific gravity being only 0.972. It is rapidly oxid- ised on exposure to the air ; and on being thrown on cold water floats about and quickly disappears, being converted into soda, which is dissolved in the water. When heated in the air it ignites and burns with a bright yellow flame. Sodium is now prepared on a commercial scale, and is employed in the manufacture of aluminium and magnesium, and in the silver-amalgamation process. Its affinity for oxygen prevents its occurrence in nature as sodium; but the compounds of soda are sufficiently abundant, forming rock -masses in the solid crust, occurring in the ocean and other saline waters, entering into the composition of many rocks and minerals, being pre- sent in all marine and in many land plants, and appearing likewise in the structure of the higher animals, which all in- stinctively swallow large quantities of its chloride. Strontium. Strontium, the metallic base of strontia, was procured from the carbonate (strontianite) by Sir H. Davy in 1808. It is ana- logous to barium, but has less lustre ; is fused with difficulty, and is not volatile. When exposed to the air it attracts oxygen, and becomes converted into strontia or protoxide of strontium. Strontium is harmless, while barium and all its compounds are poisonous. It occurs in nature as a carbonate (strontianite) and as a sulphate (celestite), both of which are noticed in Chapter XIV. Tellurium. Tellurium, another of the rare metals, was discovered by Klaproth in 1782, and named by him after the Earth- goddess Tellus. It is of a tin-white brilliant colour ; brittle and crystalline in texture ; easily fusible ; and generally found massive and disseminated along with quartz, gold, silver, antimony, arsenic, and iron pyrites, in some of the mines of Germany and Hungary Nagyag, in Transylvania, being one of its most abundant sources. Though decidedly metallic, it has close analogies to sulphur and selenium, and is usually classed with the sulphur family. It is rarely found pure, but contains a minute percentage of gold or of iron ; and the ores enumerated by mineralogists are complex and uncer- tain mixtures, as graphic tellurium, consisting of tellurium, gold, silver, and lead ; white tellurium, of tellurium, gold, silver, and 3H THE METALS AND METALLIC ORES. sulphur ; and black tellurium, of copper, in addition to the pre- ceding ingredients. Commercially, its rarity and cost exclude it from any useful application. Terbium, &c. Terbium, Erbium, Thallium, and Thorium, are rare and very little known metallic bases, derived from minerals equally rare, and of interest only to the professed mineralogist and chemical investigator. Tin. Tin, well known to the ancients, and employed in the manu- facture of their bronzes, is a metal of a silver-white colour, slightly tinged with grey, having a peculiar taste, and an odour which may be readily recognised when held for a while in the warm hand. It is considerably harder than lead ; has a spe- cific gravity of 7.3 ; and fuses at 442 Fahr. a temperature 170 below the melting-point of lead. It is very malleable when heated to about 200, and is readily beaten into leaf or tinfoil ; but it is not very ductile, though it may be drawn into wire of feeble tenacity. It is flexible, bending with a crackling noise, apparently the result of its crystallised texture, the fused metal crystallising in regular octohedrons. It is not found native (or at least very doubtfully so*) ; but it is obtained from cassiterite, pyramidal tin-ore or oxide of tin, which occurs in veins in the granitic and crystalline rocks, and in stream- drifts derived therefrom, in Cornwall, Spain, Saxony, Sweden, East India Islands, China, Australia, Peru, Bolivia, United States, Siberia, and other countries. Stannine, or tin pyrites, is a mixture of tin-, copper-, and iron-pyrites, in which the cop- per predominates, and is usually sold in Cornwall as an ore of copper. Hitherto, the chief tin-yielding districts have been Cornwall and Devon, Saxony, Banca, Billiton, Bolivia, and Peru ; but of recent years stream-drifts and veins of great richness have been discovered in Queensland and New South Wales. From re- ports on the stanniferous tracts of Australia it would appear that the drifts cover a wide area, and that the veins (traversing granites, porphyries, and crystalline schists) are numerous and accessible, thus promising to revolutionise entirely the com- mercial relations of tin and tin productions. * The nuggets known in Cornwall as Jews' fin, though sometimes found at considerable depths in the soil, are clearly artificial productions, occurring for the most part in connection with charcoal, and in the neighbourhood of old stnelting-houses. THE METALLIC ORES. 315 Cassiterite, the only commercial ore of tin, is usually associ- ated with wolfram, copper, iron pyrites, and other minerals. It is found either in blackish-brown pyramidal or prismatic crystals, or massive in granular aggregates, and not unfre- quently in rounded fragments in gravelly detritus. The name wood-tin is given in Cornwall to the kidney-shaped masses, which have a finely fibrous or radiated structure ; toatfs-eye tin to the same variety when the concretions are small and berry- like ; and stream-tin to the gravel-like ore found with detritus in the gullies and water-courses of metalliferous districts. As an ore it consists of 77.50 tin and 21.50 oxygen, with traces of iron and silica ; and being disseminated through the vein- stone, the rock must be pounded and washed before the ore can be smelted. As a geological generalisation, it is asserted that in Cornwall tin usually occurs in the upper portion of the veins, while copper is found below. In 1872, the tin ore raised in Britain (Cornwall and Devon) amounted to 14,266 tons, valued at ;i, 246,135, and the metal extracted therefrom to 9560 tons, the value of which was ,1,459,990. During the same year there were imported 1024 tons of ore, and 8342 tons of tin in blocks, bars, and ingots. The islands of Billiton and Banca are said to yield about 9000 tons of metal annually; Russia, from the stream-drifts of Siberia, 1700 tons ; and already Australia is producing upwards of 4000 tons ! The industrial applications of tin are numerous. As a metal it does not readily tarnish, and is therefore used for coating iron (tin-plate) and copper, for the manufacture of chemical vessels and apparatus, and for gas and water pipes. With other metals it forms valuable alloys, with lead, pewter; with antimony, Britannia metal ; with copper, in different propor- tions, bronze, gun-metal, bell-metal, &c. ; with zinc, the silver- foil or leaf-silver of commerce ; and its foil with quicksilver, the reflecting surface of glass mirrors. Its salts, dissolved in muriatic acid, are employed in dyeing and calico-printing ; and its foil is largely used in packing chocolate, soap, cheese, fruit, &c., against the injurious effects of the air. Titanium. Titanium, so called from its falling to a calx or lime, was discovered by Gregor, in 1789, in the menaccanite of Cornwall. It is of a dark copper-red colour, with a strong metallic lustre, which readily tarnishes on exposure to the air. As titanic acid it is a constituent of several minerals sphene, mene- kite, Brookite, rutile, and anatase. One of its most important compounds is titaniferous iron-sand, or iserine, occurring in 316 THE METALS AND METALLIC ORES. N roundish grains, generally in tertiary volcanic districts, and sometimes in such abundance as to be used for the manufac- ture of steel, of which it produces a very tough and superior kind. (See Iron.) Tungsten. Tungsten (Swed., heavy-stone) was discovered by Scheele in 1781. It is a hard brittle metal, of a light steel-grey colour and brilliant metallic lustre, having a specific gravity of 17.5. It is barely fusible at the greatest heat of the smith's forge, but when heated to redness in the open air it is converted into the peroxide (tungstic acid). Its ores, tungstates of lime, iron, and manganese, are very frequently associated with those of tin, which they greatly injure. These are wolfram, tungstate of iron and manganese ; stolzite, tungstate of lead ; scheelite, tungstate of lime ; and tungstic ochre. The metal is not used in the arts, but tungstic acid and tungstate of soda are em- ployed in dyeing, in the production of bronze powder, and for some other purposes. The amount of wolfram raised in Britain in 1872 was upwards of 88 tons, valued at .993. Uranium. Uranium was discovered by Klaproth in 1789, and so named by him after the planet Uranus, which was detected in the same year. It is obtained from several mineral species, and is, when separated, a powdery substance of a greyish-black colour, with a metallic lustre, very combustible, burning with a white light, and forming a dark-green oxide. It is reduced with great difficulty, is infusible, and has a specific gravity of 18.4. Preparations of uranium (which usually bring from 245. to 365. per pound) are employed in imparting fine orange tints to glass and to porcelain enamel ; and the uraniate of potash affords a splendid orange to the artist. The various minerals containing uranium are in general easily distinguished by the hues of yellow they communicate to glass. The following are the principal : i. Uranium ore, pechurane, or pitch-blende ; 2. Uranite, uran-mica, ur an -glimmer, or lime uranite; and 3. Chalcolite, or copper uranite all derived from the older grani- toid and crystalline schists. Vanadium. Vanadium, another of the rarer metals, of a greyish-silvery colour, was discovered by Sefstrom in 1830, in iron prepared from the iron ore of Taberg in Sweden, and named after Van- adis, a Scandinavian deity. It has since been discovered in THE METALLIC ORES. 317 the form of vanadianate of lead, or vanadinite, a mineral occurring in many localities. As a metal, the properties of vanadium are yet little known. It is regarded by modern chemists as belonging to the same series as arsenic, antimony, and bismuth. Yttrium. Yttrium is the metallic base of the earth yttria, which was discovered by Gadolin in 1794, in the quarries of Ytterby in Sweden. When separated from the silica, lime, iron, and manganese with which it is associated in yttria, the metal appears as a fine white powder, tasteless, inodorous, infusible, and insoluble in water. The ores of yttria are yttro-cerite, yttro-tantalite, yttro-titanite, &c. all complex in composition, and occurring in the older granitic and crystalline rocks. Zinc. Zinc, so well known in the arts, is a metal of a bluish-white colour, with a fine granular fracture, foliated structure, specific gravity about 7, harder than lead, but may easily be cut with a knife. At common temperatures it is tough and intractable under the hammer ; but when heated to between 220 and 320 it becomes malleable and ductile, so that it can be beaten into plates, or rolled into sheets and leaves, or drawn into wire. If heated, however, to 500 or so, it becomes brittle, and fuses at 770. It tarnishes on exposure to the air; but is little oxidated, the first-formed film of oxide long resisting the action of air and water, and thus preventing further decay. As a metal, zinc does not occur native, or at all events, very rarely and doubtfully the most authentic specimens being from Victoria, in Australia. Its chief ores are calamine, or the carbonate, occurring most abundantly in veins traversing thick-bedded limestones, along with calc-spar, ores of lead and iron, and other ores of zinc ; sphalerite or blende, the sul- phide, or "black-jack" of the miners, found also in veins in the crystalline and sedimentary rocks with other ores ; goslarite, or the sulphate, arising apparently from the alteration of blende ; zincite, or the red oxide ; and galmei, or the silicious oxide, usually found in connection with calamine. The ores of zinc are readily determined by first roasting and then fusing by the blowpipe on charcoal with copper-filings. If zinc is pre- sent, the copper will be converted into a button of brass. The ores of zinc are world-wide Germany, Belgium, Spain, and Sardinia being the main Continental repositories ; Corn- wall, Devon, Derbyshire, Cumberland, Shropshire, Wales, the 318 THE METALS AND METALLIC ORES. Isle of Man, and Ireland, the chief sources at home. In 1872, the amount of ore raised in the United Kingdom was 18,542 tons, valued at ,73,951 ; the amount of metal produced 5191 tons, valued at ^118,076; while there were imported 14,761 tons zinc ore, 32,662 tons metal, and 12,357 tons of zinc manufactures. The ores of zinc require calcination, grinding to powder, and smelting for their reduction, and the resultant metal generally contains traces of other metals, such as lead, cadmium, iron, and copper. Zinc being a cheap and light metal, is very largely employed as a substitute for lead in architecture roofing, spouts, tanks, &c. It is also used in galvanising iron, for ornamental cast- ings, in galvanic batteries, in chemical laboratories, in the production of zinc-white as a pigment,* of white vitriol, or sul- phate of zinc, as a mordant in dyeing and in medicine, and in the preparation of several other salts, of which the most valuable are the chromate as a pigment, and the chloride as a preser- vative and disinfectant. It forms various alloys with copper, the well-known and extensively employed compound, brass. The Prussians, according to Wagner, make use of zinc for cartridges. Zirconium. Zirconium, the metallic base of the earth zirconia, was dis- covered by Klaproth in 1789, in zircons from Ceylon zir- con being a silicate of zirconia, more or less coloured by iron oxide. The metal is obtained in the form of a black scaly powder, resembling that of graphite ; lustrous when rubbed ; and when ignited, burning with considerable violence. It is unknown, as yet, beyond the scientific laboratory. Such is a brief indication of the nature, position, abund- ance, and industrial applications of the metals and metallic ores. Depending upon the geologist and mineralogist for their discovery and description, upon the miner and mining engineer for their winning, the chemist and metallurgist for their reduction, and the fabricator and machinist for their ap- plications, they involve at once the highest scientific skill, and widest adaptive ingenuity. The labour and capital required at every stage of their treatment are enormous ; and paramount with the Fuels, they * From its perfect whiteness, as well as from the circumstance of its not be- coming blackened by sulphuretted hydrogen, ' ' zinc-white " is, according to Phillips ('Elements of Metallurgy'), for many purposes to be preferred to the different preparations of lead. THE METALLIC ORES. 319 are undoubtedly the most important of mineral productions. Their preparations and uses are endless, running through all our implements, utensils, and machines ; our shelter, defence, and modes of conveyance ; our articles of ornament and lux- ury our dyes, pigments, and enamels ; our drugs and thera- peutic appliances. Ours is essentially an age of metals and machinery. Our houses, bridges, railways, telegraphs, ships, weapons of warfare, steam-engines, and countless machines for spinning, weaving, milling, baking, brewing, printing, and the like, all more or less involve the application of the metals, and every year is marked by new uses and extensions. From the tiniest implement to the most gigantic machine, from the child's toy to the nation's armament, the metallic element runs through the whole ; hence the necessity of some acquaintance with their properties, preparations, and sources. To the Economic Geologist they hold out the .strongest in- centives to further research ; for much as mineralogy and metallurgy have accomplished, there are still numerous sub- stances to be examined, and new deposits to be revealed. The discovery of a new ore may change entirely the industrial aspects of a district ; the cheapening of a metal by a few shillings a ton may increase its applications a hundredfold. It is his duty to be ever on the alert, allowing no substance to escape his notice, and no indication of an ore to pass without sufficient examination. To Britain, her metalliferous products are of the utmost im- portance not only employing millions of her population in their winning, smelting, and fabrication, but conferring upon her unrivalled mechanical power, and opening to her a way and a market in every region of the globe. Some idea of their magnitude and value may be gathered from the following summary of the MINERAL PRODUCE of the United Kingdom for the year 1872 : Ores. Iron ore 15,586,357 tons, valued at 7,774,874 443.758 1,246,135 1,146,155 73-951 39-470 38,865 17,964 993 130 8,227 Copper ore, 91,983 14, 266 83,068 1 8 Z4.2 Pyrites ore, . Manganese ore, . Arsenic ore, . Wolfram ore, Chloride of barium, Ochres and umbers, Bismuth ore, Cobalt ore, 65,916 7.773 5.I7I 88 65 3,326 2 I 10,790,542 320 THE METALS AND METALLIC ORES. Metals. Pig-iron,, .... 6,741,929 tons, valued at 18,540,504 Coppery . . . . : 5,703 583,232 /"V . 9,560 1,459,990 V- 60,455 ., ,, 1,209,115 ! nc 5>i9i ,, ,, 118,076 ./^ n y er ' . 628,920 ounces ,, 157,230 - Other metals, ... . (estimated) 2,500 22,070,447 Salts and Earthy Minerals. Rock-salt, 1,309,497 tons, valued at 654,748 1,200,000 ,, ,, 450,000 9,092 ,, ,, 7,078 80 ,, 40 35,000 ,, ,, 50,000 (estimated) 650,000 Clays, Barytes, Fluor-spar, Coprolites, Other earthy minerals, 1,811,826 Total Mineral and Metallic Produce. Metals, value of, as above 22,070,447 Coals, ,, ,, 46,311,143 Minerals, earthy, &c., ,, 1,811,826 70,193,416 Works which may be consulted. Dana's ' System of Mineralogy ; ' Percy's ' Metallurgy; ' Phillips's * Ele- ments of Metallurgy;' Kerl's 'Metallurgy,' translated, with additions, by Crookes and Rohrig; Wagner's ' Chemical Technology;' Knapp's * Chemical Technology ; ' lire's * Dictionary of Arts and Manufac- tures;' 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 de- rived 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 char- acter and value of the products derived from the several systems, and in particular as developed in the British Islands. POST-TERTIARY SYSTEM SUPERFICIAL ACCUMULATIONS. Silitious sands, for mortar, metal-moulding, glass-making, tem- pering 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, drain- pipes, earthenware, porcelain, tobacco-pipes, and other fictile ob- jects ; for agricultural admixtures, &c. Cfoyjand river-muds of a calcareo-ferruginous character, for the manufacture of hydraulic cements. Silitious silts and microphytal earths, for bath-bricks and other polishing preparations ; for giving body and consistency, under the name of kiesel-ghur, to dynamite. X 322 GENERAL SUMMARY. Shetland 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 pur- poses. Bituminous exudations, as naphtha, petroleum, and asphalt, large- ly 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 Plceocarpus, &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 brine- springs, salt-lakes, and salinas. Extensively and variously em- ployed in the arts and manufactures, in medicine, and as top-dress- ings 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, medi- cines, &c. Guano, the desiccated and semi-mineralised droppings of sea- birds, 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 purifi- cation of gas. Titanic iron-sand, found along many shores, and sometimes col- lected 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 admix- tures, &c. Clays of various qualities, for the manufacture of bricks, tiles, pipes, pottery, porcelain, and other fictile purposes. GENERAL SUMMARY. 323 Limestones of various origins and qualities, for mortar, agricul- tural 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-of- Paris, stuccoes, cements, and the like ; also for agricultural top- dressings 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 de- veloped 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, fur- nace-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 deter- gent 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 per- centage of soluble silica, and used for the procuring of this sub- stance. Lignites and bituminous coals, occurring chiefly in foreign coun- tries, 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. 324 GENERAL SUMMARY. Sandstones and flagstones of fair quality, for building and pav- ing 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, decora- tion, mortar, agriculture, and allied uses. Shelly freestones (Forest marble), occasionally used for orna- mental 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 occasion- ally, employed in the fulling or deterging of woollens. Bituminous shales, occasionally used, but with indifferent suc- cess, 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 brick- making. Aluminous and pyritous shales, for the preparation of alum and copperas, and occasionally for the extraction of sulphur and sul- phuric acid. Argillaceous limestones, for the manufacture of hydraulic mor- tars and cements. Jet, chiefly for the manufacture of personal ornaments. Ironstones (clay carbonates), in thick beds like those of Cleve- land, and yielding from 28 to 33 per cent of metallic iron. TRIASSIC SYSTEM. Sandstones, often of indifferent quality, for building and flag- ging purposes. Shelly limestones (muschelkalks), for mortar, agriculture, and other purposes of ordinary limestone. Gypsum and alabaster, the former for the manufacture of plaster- of-Paris, agriculture, &c. the latter for ornamental purposes. GENERAL SUMMARY. 325 Rock-salt, used in the natural as well as in the refined state, for many purposes in the arts and manufactures, preparation of soda, earthenware - glazing", glass-making, agriculture, preservation of food, as a condiment, &c. Brine-springs, yielding on evaporation from 4 to 7 per cent of salt, and of frequent occurrence. Double salts of soda, potash, &c. (carnallite, polyhalite, &c.), from which are extracted salts of soda, potash, and the like all largely made use of in the arts and manufactures. PERMIAN SYSTEM. Sandstones of various qualities, for building and flagging pur- poses. Magnesian limestone of varied texture and composition, em- ployed as a building-stone, as an ordinary limestone, and also for the extraction and preparation of magnesian salts, the carbonates and sulphates. Copper-slate, a hard cupriferous slate, mined in Germany as an ore of copper. CARBONIFEROUS SYSTEM. Sandstones ?cc\& flagstones of various colours, textures, and thick- ness, for building, flagging, millstones, grindstones, crushers, &c. Shales, bituminoiis, aluminous, and Pyritous, for the distillation of paraffin and paraffin-oils ; for the preparation of alum and sul- phate of iron ; and for the extraction of sulphur and sulphuric acid. Fire-clays, extensively used for the manufacture of fire-bricks, furnace and oven slabs, retorts, glass-smelting pots, sewage-pipes, and other purposes industrial and ornamental. Limestones of various origin and quality, common and hydraulic, for mortar, cements, metal-fluxing, agricultural purposes, bleach- ing, tanning, &c. ; and occasionally, when sufficiently crystalline and attractive in colour or figure, for marble. Magnesian and gypseous limestones, found chiefly in foreign coal-fields, and used as ordinary limestones and gypsums. Fluor-spar (blue John or Derbyshire spar), in veins and nests in the thicker-bedded limestones, and used for ornamental objects. Barytic "veins, yielding sulphate and carbonate, and used in glass-making, sugar-refining, pigment-admixture, and other pur- poses. Bituminous coals and anthracites, in many varieties and quali- ties, suitable for common fuel, for coking, metal-smelting, steam- raising, gas and oil distillation, and numerous kindred purposes. Ironstones (carbonates), in bands and nodules, known as clay- bands and black-bands the latter containing sufficient coaly matter for its own calcination, and both often yielding upwards of 40 per cent of metallic iron. 326^ GENERAL SUMMARY. y Hcematites, or oxides of iron, in nests and masses in carbonifer- ous limestone (as in Furness), and often yielding upwards of 60 and 70 per cent of metallic iron. Ochre, or the hydrated oxide of iron, resulting from the decom- position of ironstones, and largely used as a colouring material. Metalliferous veins, or veins of lead, argentiferous lead, zinc, and antimony, in the thick-bedded carboniferous limestones. OLD RED SANDSTONE AND DEVONIAN. Sandstones of various colours and qualities, some of them dur- able, and well suited for building purposes. Flagstones of unequalled straightness and varied thickness, for pavements, cisterns, lining-slabs, &c. Tilestones of varied thickness and quality, for roofing purposes. Limestones, chiefly in the Devonian strata, for building, mortars, agriculture, and also for ornamental marbles. Barytic veins, occasionally of commercial value. Rock-salts and brine-springs, as in North America. Metalliferous veins, as haematite, lead, copper, silver, and doubt- fully of mercury. SILURIAN AND CAMBRIAN SYSTEMS. Sandstones of indifferent quality, for building, for flagging, and for tilestones. Clayey shales (outcrops of Wenlock beds), locally used for brick-making. Limestones of various qualities, for building, mortar, fluxing, agriculture, and other purposes. Slates of various colours and textures, of unrivalled quality for roofing, cistern-slabs, table-slabs, wall-linings, paving, enamelling for ornamental purposes, and other uses. Barytes, sulphate and carbonate, in veins, and employed in glass-making, sugar-refining, pigment-admixtures, &c. Apatite, or phosphate of lime, in veins, and mined for the manu- facture of artificial manures. Umber and other ochres, the products of decomposition, raised in considerable qualities for the preparation of pigments. Pyrites (iron and copper), extensively raised in some localities for the manufacture of sulphur and sulphuric acid, copper being often recovered from the waste residue. Metalliferous veins, often of vast richness and value, as gold, platinum, silver, mercury, copper, tin, lead, iron, manganese, and other metals. LAURENTIAN AND METAMORPHIC. Slates of various colours and qualities, for roofing, cisterns, table-slabs, wall-linings, paving, and similar purposes. GENERAL SUMMARY. 327 Limestones and marbles, used as ordinary limestones, but usu- ally for ornamental purposes. Quartzites, for grinding and crushing purposes. Serpentines of various colours, employed in architectural deco- rations and ornament. Asbestos, in veins, for steam-packing, lamp-wicks, gas-grates, and other fire-resisting purposes. Meerschaum, in veins, for the manufacture of tobacco-pipes, &c. Steatite, or potstone, for furnace-hearths, oven-soles, pipkins, and other refractory uses. Magnesite, in veins and stratiform masses, for the extraction of magnesia, and the preparation of its salts. Apatite, in veins, employed in the preparation of phosphatic manures. Cryolite, in veins, used as an ore of aluminium. Graphite, in nests and veins, extensively employed in the manu- facture of writing-pencils, crucibles, &c., and as a polisher and lubricant in metal-working and machinery. Umber and other ochres, in veins, for the manufacture of pig- ments. Gems and precious stones, as accessory minerals in schists, and occurring in fissures, veins, and drusy cavities rock-crystal, topaz, ruby, emerald, beryl, tourmaline, lapis lazuli, garnets, &c. Metalliferous veins, yielding gold, platinum, silver, mercury, copper, tin, lead, zinc, antimony, cobalt, iron, manganese, and other useful metals. VOLCANIC ROCKS. Lavas of various colours and textures, for building, road-ma- terial, milling and crushing stones, &c. Pumice, in blocks or powder, as a cheap and efficient reducing and polishing substance. Obsidian, or volcanic glass, used by primitive people for cutting implements, spear and arrow heads, and the like. Pozzuolana and trass, varieties of volcanic ash, used in the manufacture of Roman or hard-setting hydraulic cement. Sulphur and sulphiir-earths, for the extraction of sulphur, and used in the manufacture of gunpowder, sulphuric acid, and nu- merous other industrial and medicinal purposes. Borax and sal-ammoniac, found in volcanic areas, and products of thermal action ; used variously in the arts and in medicine. Gems and precious stones, occurring as accessory minerals in volcanic systems agate, calcedony, olivine, spinelle, vesuvianite, &c., &c. TRAP-ROCKS. Basalts and greenstones, for building-stones, causeway-courses, kerbstones, road-metal, and similar uses. 328 GENERAL SUMMARY. Felstones and porphyries, for building, causewaying, macadam- ising ; and the latter occasionally for ornamental purposes. Leckstones, or granular trap-tuffs, for oven-soles, furnace-hearths, and similar uses. Precious stones, in geodes and drusy cavities, as rock-crystals, agate, carnelian, calcedony, jasper, olivine, &c. GRANITIC ROCKS. Granites and porphyritic stones, for building, for decoration, monumental monoliths, causeway-courses, kerbstones, road-metal, and kindred uses. Granite blocks, for grinding and crushing purposes. Felspathic or decomposing granites (Cornish stone), as an in- gredient in porcelain manufacture. Syenites and syenitic granites, less abundant, but employed for similar purposes as the ordinary granites. Precious stones, as accessory minerals occurring in granite rocks rock-crystal, amethyst, cairngorm, topaz, tourmaline, beryl, emerald, garnet, &c. Such is a brief summary of the economic products usually obtained from the respective geological systems, and especially as developed in the British Islands. Lithologically speaking, the strata of a system may vary considerably at different parts of its development, and in distant countries may be still more dissimilar. Notwithstanding these variations, which must ever be incidental to sedimentary deposits, there is always a cer- tain amount of resemblance, and it is this resemblance which should lead to a search for the same products in the same chronological system. Take, for example, the Trias of Eng- land and the Trias of Germany. Although the muschelkalk of the latter has no equivalent in the former, yet the other members of the system sandstones, rock-salts, gypsums, and saliferous marls are sufficiently alike to furnish the same kind of industrial products. Or take the coal-formations of Wales or of Nova Scotia. Although the limestones of the former be carbonates, and those of the latter magnesian and gypseous, yet all the other beds sandstones, shales, fire-clays, coals, and ironstones are so similar, that those from the one field might be mistaken for those from the other. The resem- blance, or rather identity, of the unstratified or pyrogenous locks is still more striking. The granites and syenites of Egypt and Norway, the basalts and greenstones of Scotland and Germany, and the lavas and tufas of Italy and the Sand- wich Islands, are all but identical in composition; and the pro- GENERAL SUMMARY. 329 ducts obtained from any one of these groups in one region, may be sought for, with all but absolute certainty, in another. It is in this way that a systematic summary of economic sub- stances becomes of use to the practical geologist ; for whether surveying at home or abroad, he may naturally expect to find in the respective systems a certain similarity of available pro- ducts. Not that there are not wide exceptions to this rule the cretaceous system of England and the cretaceous sys- tem of North America, for example but because it is useful to know that certain substances are characteristic of certain formations, where these formations are fully and typically developed. The practical geologist should have a higher aim, however, than merely searching for substances already known, and on which the arts and manufactures have stamped a certain value. This is of itself good and commendable, and will bring with it its own reward ; but he should at the same time endeavour to extend our knowledge by noting every rock, mineral, and ore that comes under his observation, examining its nature, and, in conjunction with the technologist, trying to discover in what way and how far it can be rendered available to the arts and industries. The utilisation within recent years, for instance, of the ironstones of Cleveland, the oil-shales of Scotland, and the phosphatic nodules of the greensand, with all the commercial and social consequences that have flowed and are flowing from them, are things which hold out the incentive to the careful inquirer of discoveries equally novel and equally re- munerative. It is true the theoretic or scientific aspects of geology are replete with interest and attraction, and to many these form the bourne and boundary of their investigations ; but it need not be necessarily so, for its practical or economic aspects are, though in another way, equally interesting and important. To trace the history of our planet through all her former aspects and mutations, is no doubt a high and inspiring theme; but science is never more exalted than when, following her legitimate functions, she stoops to administer to the wants of our common humanity. Whatever tends to increase man's mastery over the forces of nature extends his domain ; what- ever improves the physical conditions of human life, lengthens the lever of its intellectual and moral advancement ; and thus the discovery of a new economic product is as important in its own way as the solution of a scientific problem. The scientific problem may interest only a few, and affect others remotely; the new product is a direct contribution to the general wealth and wellbeing of society. 33O GENERAL SUMMARY. But while this cannot be gainsaid, the student, as he values his own intellectual life and growth, should never forget that the discovery of scientific truths stands on a higher platform than mere invention, or the application of these truths to industrial requirements. Both are good and necessary, and cannot be ignored ; but without discovery invention is help- less. The one creates, the other only adapts. Commercially speaking, invention may bring rewards which discovery cannot supply ; but without discovery invention would soon languish in hopeless stagnation. The one is the spirit of progress, the other merely the bodily members which that spirit animates and controls. INDEX. ABERDEEN granites, 61. Adits, in vein-mining, 149. Agates as ornamental stones, 86. ii as precious stones, 277. Agriculture and geology, 32-49. Alabaster, gypseous and calcareous, 84. Albertite or Albert coal, 175. Alkaline waters, 251. Alum, sources and preparation of, 234. ti as a fire-resister, 213. ii in medicine, 259. Alumina, salts of, 233. Aluminium, its ores and uses, 289. Amber, for ornamental uses, 266. Ambrite, fossil gum-resin, 267. Amethysts as precious stones, 275. Ammonia, salts of, 233. ii salts as manures, 47. ii in medicine, 259. Amygdaloid as an ornamental stone, 79. Anthracite as a fuel, 165. ii analyses of, 165. Antimony, its ores and uses, 290. ii in medicine, 260. Apatite as a manure, 44. Apcenite, or Ransome's patent stone, 100. Aqueducts for canals, 115. Arbroath pavement, ucx Architecture and geology, 58-88. Arenaceous rocks, 18. Argillaceous rocks, 19. Arkansas oilstone, 206. Arsenic, its ores and uses, 291. ii in medicine, 260. Artesian wells, 123. Artificial gems or pastes, 280. Asbestos as a fire-resister, 215. ti for steam-packing, &c., 215. Asphalt as a light-producer, 176. Asphaltic cements, 97. BARDIGLIA marble, 82. Barium and its ores, 292. ii in medicine, 260. Barytes, salts of, 236. Basalts as building-stones, 63. ii for ornamental purposes, 79. Bath-brick, nature and uses, 202. Bath, thermal springs, 246. Batts for sharpening, 205. Bauxite as an ore of aluminium, 290. Beer, calcareous building-stone of, 78. Bench-working in quarries, 132. Beryl as a precious stone, 272. Bismuth, its ores and uses, 292. ti in medicine, 260. Bitumens as light-producers, 174. Bituminous cements, 97. t coals as fuels, 162. ii shales, distillation of, 176. ii springs, 256. Blackband ironstone, 302. Bloodstone for ornaments, 279. Blue John for ornaments, 85. Bogwood for ornamental uses, 218. Boles, various, for colouring, 218. Bolsover Moor stone, 75. Borax and boracic acid, 230. Boring-machines, various, 124. Borings, journals of, 137. Bort, or black diamond, 204. Boulder-clay group, 25. ii cuttings through, 102. Brick-clays, 186. Bridge of Allan waters, 250. Bromine in medicine, 260. Brown-coals as fuels, 160. Building-stones, 59-78. Burnishers, mineral, 206. Burrstones for milling, 196. Buxton thermal waters, 245. CADMIUM, its ores and uses, 293. ti in medicine, 260. Caesium as a metal, 293. Cairngorms as precious stones, 275. Caithness pavement or flagstone, no. Calcareous rocks, 19. ti manures, 43. Calcedonies as precious stones, 276. Calcium as a metal, 296. Cambrian system, 27. Canals, construction of, 115. Cannel-coals for gas, 177. it for ornamental uses, 268. Carbonaceous rocks, 20. ii manures, 42. Carboniferous system, 27. n products, 325. ii limestones, 73, 85. 332 INDEX. Carbuncle as a precious stone, 274. Carnallite, 232. Camelians as precious stones, 278. Carrara marble, 82. Cements, various, 93, 95, 97. Cerium and its ores, 294. if in medicine, 260. Chalk as a manure, 43. Chalks, drawing, various, 222. Chalybeate waters, 254. Chance's patent stone, 102. Charley Forest oilstone, 206. Cheeks or walls of veins, 146. Chemical elements, table of, 14. China-clay, 183. Chlorine in medicine, 260. Chromate of iron, 294. Chrome colours, 295. Chromium, its ores and uses, 294. Chronological arrangements of formations, 23- Cipplino marble, 82. Civil engineering and geology, 105-129. Clayband ironstone, 302. Clays we fabricate, 182. Clyde, improvement of, 120. Coal-mining, interruptions to, 143. Coal, produce of United Kingdom, 180. Coals, bituminous, as fuels, 162. n British, analyses of, 164. Coal-working, method of, 138. Cobalt, its ores and uses, 295. Coke as a fuel, 167. Colours for glass or porcelain, 192. Columbium as a metal, 309. Composition of rocks, 13. Concrete building blocks, 99. ii for streets and roads, 98. n walls, 98. n piping, 99. Concretes, nature and preparation of, 98. Connemara serpentine, 80. Contra or counter veins, 147. Copal, subfossil gum, 322. Copper as a native metal, 287. n its ores and uses, 295. ii sulphate of, 235. ii in medicine, 260. Copperas or sulphate of iron, 235. Coprolitic nodules as manure, 44. Corundum as a gem, 268. Costeaning for veins, 148. Crayons or drawing-chalks, 222. Cretaceous system, 25. n products, 323. Crocus, for polishing metals, 201. Cross courses or veins, 147. Crushing wheels and blocks, 199. Crust, the rocky, nature and structure of, 8-31. Cryolite as an ore of aluminium, 290. n composition of, 231. Cuttings and tunnellings for canals, 115. DALBEATTIE granite, 61. n granite quarries, 134. Decorative stones, 78-88. Deep-well borings, 125. Derbyshire sandstones and grits, 71. ii spar, for ornaments, 85. Detergents of mineral origin, 224. Devonian system, 27. Devonian products, 326. ii limestones, 73, 83. Devonshire granites, 61. ii marbles, 83. Diamond as a gem, 265. n for cutting and polishing, 204. Didymium as a metal, 297. Dinas fire-bricks, 211. Docks and harbours, construction of, 117. Draining, objects of, 39. Dredging and widening of rivers, 120. Durham sandstones, 70. Dyes from minerals, 223. Dyke and dyke-faults, 144. Dykes, illustrations of, 10. EARTHY springs, 246. Eclogite as an ornamental stone, 86. Edinburgh Castle rock, 9. ii sandstones, 69. Elements, chemical, table of, 14. Embanking and warping lowlands, 121. Embankments and bridges for roads, 108. n n for railways, 114. ii and aqueducts for canals, IT 5- Emery, nature and uses, 202. n wheels, 198. Enamels, glazes, and colours, 192. Encrinal marbles, 82. Engineering, civil, and geology, 105-129. Erbium, metallic element, 314. FAULTS, illustrations of, 10. n various, in coal-fields, 146. Felspars for ornamental uses, 273. Felstones as building-stones, 63. Fictile arts and geology, 182-194. Fifeshire sandstones, 70. Figure in marbles, 81. Fire-clay and its manufacture, 208. Fire-clays, 188. ii analyses of various, 209. Fire-resisting substances, 208-216. Firestones, various kinds, 213. Flagstones for footpaths, no. Flour, fossil, 189. Fluor-spar for ornaments, 85. Forest-growth and soils, 36. Forest marble, 84. Forfar flagstones, nature of, no. Formation, stratified, arrangement of, 23. Fossil flour, 189. n bricks of, 212. Franklinite, ore of iron, 302. Fremy on the formation of coals, 166. Fuels, fossil, 156-168. n artificial, 168. Fuller's earth, nature and uses, 223. Furnace-slag for roads, 109. Fusible metals, 293. GALENA, sulphide of lead, 305. Garnets as precious stones, 274. Gas and naphtha springs, 170. Gems and precious stones, 263-282. Gems, artificial, 280. General summary of products, 321. Geology, theoretical and practical, i. n applied, illustrations of, 2-5. Giallo-antico marble, 82. Gilslaud waters, 248. INDEX. 333 Glacial epoch, nature of, 25. Glasgow sandstones, 69. Glass manufacture, materials for, 191. ii varieties of, 190. Glauberite, 229. Glauber-salt, sulphate of soda, 229. Glazes, enamels, and colours, 192. Glen Tilt marble, 83. Glucinum as a metal, 298. Goaf or gob in coal-mining, 140. Gold as a native metal, 284. ii its ores and uses, 298. ii in medicine, 260. Gossan of veins, 148. Granite, common, for building, 61. ii common road-material, 109. ii for roads and streets, 109. .1 graphic, 62. ii porphyritic, for building, 61. ii quarries, 134. Granites and porphyries for building, 59. ii for ornamental purposes, 78. Granitic products, 328. ii rocks, 29. Graphite for crucibles, 212. ii for pencil-making, 221. Gravity, specific, of rocks, n. Greenstone quarries, 136. Greenstones as building-stones, 63. tr for roads and streets, 109. Grinding materials, 195. Grindstones, sandstones, and grits, 197. Grits for building purposes, 66. Grouting with mortar, 92. Grover, Lieut., on fire-clays, 209. Guano as a manure, 45. Guanos, composition of, 46. Gypsum as a manure, 43. HADE or underlie of veins, 146. Haematite, red oxide of iron, 300. Harbours, construction of, 117. Hardness of rocks, scale of, ii. Harrogate springs, 248. Holystones for scrubbing, 200. Hones for whetting, 204. Horni sing of footpaths, in. Hot springs, various, 240-256. Hydraulic limestones, nature of, 94. ii placer-working, 153. IGNEOUS rocks, 22. ii classification of, 28. Ilmenite, titaniferous iron, 301. Indium as a metal, 298. Inland streams, improvement of, 120. Introduction, 1-7. Iodine in medicine, 260. Iridium as a metal, 298. Iron as a native metal, 288. if its ores and uses, 299, i meteoric, 288. i statistics of, 302. ii in medicine, 260. Iserine, titaniferous iron-sand, 301. JADE as an ornamental stone, 86. Jaspers as ornamental stones, 86. if as precious stones, 279. Jersey granite, 61. Jet for ornamental uses, 267. Jurassic or Oolitic system, 26. KAOLIN or China-clay, 183. Kentish rag, 78. Kerbstones, materials for, in. Kimmeridge shale or coal, 176. LAKES and reservoirs for water-supply, 126. Land, surface value of, 51. it mineral value of, 53. ii valuation and geology, 50-57. Landed estates, works, &c. , 57. Landscape or surface amenity, 52. Lanthanium as a metal, 304. Lapis lazuli as a precious stone, 273. Laurentian products, 326. Lavas as building-stones, &c., 64. Lead, its ores and uses, 304. ii in medicine, 260. Leckstones for oven-soles, 214. Liassic products, 324. Light-producing substances, 169. Lignites and brown coals as fuels, 160. Lime in medicine, 260. Limes and mortars, 89. Limestones for building purposes, 72. tf for hydraulic cement, 95. if for mortar, 90. u mortar, qualities of, 94. Limonite, brown oxide of iron, 301. Lipowitz on cements, quoted, 95. Lithia in medicine, 261. Lithium as a metal, 306. Lithographic materials, 222. Littoral concrete, 117. Lizard Point serpentines, 80. London wells, discharge of, 125. Long-wall work, 140. Lumachello marble, 82. MADREPORE marbles, 83. Magnesia, salts of, 232. if in medicine, 261. Magnesian limestones for building, 75. Magnesium as a metal, 306. Magnetic iron ore, 300. Malachite as an ornamental mineral, 87. u for ornamental uses, 279. Malm-rock of Surrey, 102. Manganese, its ores and uses, 307. u in medicine, 261. Mansfield building-stone, 76. Manures, mineral, 41. Maps and sections, construction of, 29. Marble, black, 82. Marbles for decorative purposes, 81. Marl as a manure, 42. Mastics or mastic cements, 96. Medicines, mineral, 259. Meerschaum, 189. Melrose chalybeate, 255. Mercury, its ores and uses, 307. u as a native metal, 287. u in medicine, 261. Metallic produce of Britain, 319. ii salts, 235. Metals and metallic ores, 283-320. u metalliferous rocks, 22. Metamorphic products, 326. Millstones, burrs, 196. ii grits, 196. Mine engineering and geology, 130-155. Mineral groups and species, 15-18. u manures, '4 1. 334 INDEX. Mineral leases, 53. ir produce of Britain, 319. n and thermal springs, 240. Minerals and their compounds, 21. Mining in stratified rocks, 136. ti in veins, 145. Mispickel as an ore of arsenic, 291. .a Mixed rocks, classifications of, 18. Moffat waters, 248. Molybdenum as a metal, 308: Mortar limestones, nature of, 90. Mortars, concretes, and cements, 89-101. Mud springs and baths, 256. NAPHTHA and gas springs, 170. Natron, carbonate of soda, 228. Natural grits in coal-fields, 143. Newcastle sandstones, 70. Nickel, its ores and uses, 308. Niobium as a metal, 309. Nips-out in coal-seams, 143. Nitratine, nitrate of soda, 229. Nitre or saltpetre, 231. OIL-SHALES, analyses of, 177. Oil-wells, 171. Old Red Sandstone, 27. ti products, 326. Onyxes as precious stones, 278. Oolitic or Jurassic system, 26. it products, 324. it freestones, 76. Opals as precious stones, 278. Ores, the metallic, 288. Ornamental and decorative stones, 78- 88. Orpiment or king's yellow, 291. Osmium as a metal, 309. PALLADIUM as a native metal, 287. Paludina marble, Sussex marble, 84. Parian marble, 82. Pastel pigments, 221. Pastes or artificial gems, 280. Patent fuels, various, 168. Peat as a fuel, 156. ii as a light-producer, 175. n as a manure, 42. Pelopium as a metal, 309. Permian system, 26. ii products, 325. ii limestones (magnesian), 75. P.etroleum springs and wells, 171. ii as a fuel, 168. n in medicine, 261. Petworth marble, 84. Phosphate of lime as a manure, 44. Phosphorus in medicine, 261. Piers and sea-walls, materials for, 117. Pigments, dyes, and detergents, 217-225. i metallic, 220. M mineral, 218. n pastel, 221. Pillar-and-stall work, 139. Pipe-clays, 185. Pitch, as a light-producer, 174. Pitcaithly waters, 250. Pits, natural, in Belgian coal-fields, 143. Placer-working, deep and shallow, 151. Plaster of Paris, nature of, 93. Plasters, nature and composition of, 92. Platinum as a native metal, 286. Polishing materials, 199. Polyhalite, 232. Porphyries and granites for building, 59. n for building, 62. ii for ornamental purposes, 79. Portland cement, 96. Portspy serpentines, 80. Positions of rocks, 13. Post-tertiary system, character of, 25. n products, 321. Potash, salts of, 231. n as manures, 47. Potass as medicine, 261. Potassium as a metal, 310. Pots tone or steatite, 214. Pottery clays, 185. Pozzuolano for hydraulic cement, 95. Precious stones and gems, 263-282. Puddingstone of Herefordshire, 87. Pulping wheels, 199. Pumice, origin and uses, 202. Purgative waters, 253. Pyrites, iron, 302. Pyrogenous rocks, 22. QUARRIES in stratified rocks, 131. n in unstratified rocks, 134. Quarrying or open-working, 131. Quartzites for milling, 197. Quicklime as a manure, 44. RAGSTONES for sharpening, 205. Railway construction, in. n cuttings and tunnels, in. Ransome's patent stone, 101. Realgar as an ore of arsenic, 271. Refractory substances, 208-216. Reverse-faults, 144. Rhodium as a metal, 210. Ridered veins, 147. River improvement, 119. Road-cuttings, 106. Road-making, 106. Road-materials, various, 108. Rock-crystal as an ornamental stone, 86. Rock-crystals for ornamental uses, 275. Rock-formations, chronological arrange- ment of, 23. Rock-salt, 226. Rocks, mineral and chemical, composition of, 13. n mixed, classification of, 18. n stratified and unstratified, 8-10. n structure and texture of, n. Rocky crust, the, nature and structure of, 8-31. Rosso-antico marble, 82. Rottenstone as a polisher, 201. Rowley rag, fusion of, 102. Rubidium as a metal, 310. Ruby as a gem, 269. Ruthenium as a metal, 311. SALINAS of South America, 47. Saline manures, 46. n rocks, 21. if waters, 249. Saltpetre, nitrate of potash, 231 Salts and saline earths, 226-239. Sands for mortar, 91. n for polishing, 200. ti we vitrify, 190. INDEX. 335 Sandstone, black, of Carnock, 70. Sandstones for building purposes, 66. ii analyses of various, 66. ii from the Oolitic system, 72. ii from Triassic system, 71. 11 from Permian system, 71. ir from the Carboniferous system, 69. ir from the Old Red Sandstone, 68. .. from the Silurian system, 68. Sapphire as a gem 270. Satin-spar for ornaments, 85. Scarborough springs, 254. Scheele's green pigment, 291. Sculpture, stones suitable for, 78. Sea-embankments, 121. Sea-walls, materials for, 117. Sections and maps, construction of, 29. Selenitic mortar or cement, 92. Selenium as a metal, 311. Septaria or cement stones, 94-96. it as ornamental stones, 86. Serpentines for ornamental purposes, 79. Sewers and sewage, 128. Shales, bituminous, distillation of, 176. Shap granite, 61. H granite quarry, 135. ii waters, 248. Shell-marbles, 82-84. Sheading and shoadstones, 148. Siderite, carbonate of iron, 302. Sienna marble, 82. Silica, soluble, 102. Silicious rocks, 20. Silicium as a metal, 311. Silurian and Cambrian products, 326. ii system, 27. Silver as a native metal, 287. ti its ores and uses, 311. H in lead ore, 312. H in medicine, 261. Sinking and shafting for coals, &c., 137. Slaking of lime, 91. Slates and schists for building, &c., 64. ti for decorative purposes, 79. ii for slabs and roofing, 65. Smalt, its preparation, 295. Smyth, Warrington, on coal-mining, 140. Snakestone or Water-of-Ayr stone, 206. Soda, salts of, 226. ii salts as manures, 47. ii in medicine, 261. Sodium as a metal, 312. Soils and subsoils, nature of, 33. ii of disintegration, 34. n of transport, 36. ii texture of, 23. n and forest-growths, 36. ii fertile admixture of, 37. Soluble silica of Surrey, 102. Sombrero guano as manure, 45. Spathose iron ore, 302. Specific gravity of rocks, 1 1. Spiegeleisen, composition of, 307. Springs and surface- wells, 122. n mineral and thermal, 240-256. n mineral, classification of, 244. Stassfurt, salt-beds of, 232. St Catherine's Well, Edinburgh, 173, 256. Steatite as a fire-resister, 214. Steel, preparation of, 302. Step-faults, 144. Stibnite as an ore of antimony, 290. Stirling sandstones, 69. Stourbridge fire-clay, 208. Strathpeffer waters, 248. Stratified wells, quarrying of, 131. n systems of Europe, 24. Stream or placer working, 151. Strontia, salts of, 237. Strontium as a metal, 313. Structure of rocks, n. Stucco, nature and preparation of, 93. Sulphur, sources and uses of, 237. n springs, 246. it in medicine, 261. Surface-wells, 122. Surveys of coal and other fields, 136. Sussex marble, 81. Syenite and syenitic granite for building, 62. Systems, stratified, of Europe, 28. TANTALUM as a metal, 309. Tellurium and its ores, 313. Terbium, metallic element, 314. Terra cotta, 188. Tertiary system, 25. products, 322. Texture of rocks, n. Thallium, metallic element, 314. Thermal springs, 240. Thorium a metallic element, 314. Tidal rivers, improvement of, 119. Tilestones from various formations, 65. Tin, its ores and uses, 214. Tiree marble, 83. Titanium and its compounds, 315. Topaz as a gem, 271. Trappean rocks, 29. i products, 327. Trass for hydraulic cement, 95. Triassic system, 26. i products, 324. Trinidad pitch-lake, 174. Tripoli as a polisher, 200. Trona, sesquicarbonate of soda, 229. Trough-faults, 144. Tungsten and its compounds, 316. Tunnels through various formations, 113. Turquoise as a precious stone, 270. Tyne, improvement of, 120. ULTRAMARINE, preparation of, 219. Umber as a colouring matter, 219. Unstratified rocks, classification of, 28. it if quarrying of, 134. Uranium and its compounds, 216. VAL DE TRAVERS asphalt, 97. Vanadium and its compounds, 316. Varnishes, mineral, 222. Vein-mining, 145. Veins, theories and generalisations, 150. n various, described, 146. n working or winning, 149. Verde antique (serpentine), 81. (marble), 82. sulph. of ( Vitriol, blue, sulph. of copper, 255. n green, sulph. of iron, 235. n white, sulph. of zinc, 236. Volcanic products, 327. n rocks, 29. 336 INDEX. WALLS or cheeks of veins, 146. Warping, practice of, 121. Wash-outs in coal-fields, 143. Water and water-supply of towns, 121. ii ir for canals, 116. ir ti for railways, 114. Water-bearing beds, 124-126. Water-of-Ayr stone, 206. Waters, earthy, 246. ii indifferent, 245. ir sulphur, 246. Water-works, various, 127. Waves, impact of, 118. Wealden products, 323. Wells, deep-borings, 125. if of London, depth and discharge, 125. Welsh slate or oilstone, 206. Werner on veins, 151. Whetstones, various, 204. Whiting or Spanish white, 219. Wicklow granite, 61. Woodhall salt-spring, 257. YORKSHIRE sandstones, 70. Yttrium and its ores, 317. ZINC, its ores and uses, 317. ii sulphate of, 256. ii in medicine, 262. Zirconium as a metal, 318. Zircons as precious stones, 274. THE END. PRINTED BY WILLIAM BLACKWOOD AND SONS, EDINBURGH. 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