Chlorides, etc.III. Common Salt, the chloride of the metal Sodium, is exhibited in case 8f, and Fluor-spar, a fluoride of Calcium belonging to the same division, begins at case 7e.Oxides.IV. The next division consists of compounds of Oxygen and includes most of the stony Minerals.Cuprite (10a), an important ore of Copper (Copper 89, Oxygen 11, per cent.), is at first ruby-red in colour, but becomes blackened by exposure to light.Spinel (10e), in its transparent varieties, is one of the precious stones; the deep red being the Spinel Ruby (less dense and less hard than the true Ruby), the rose-tinted the Balas Ruby, and the yellow or orange-red the Rubicelle of the jewellers: sometimes, it has a dark blue colour. On account of their hardness, the less valuable specimens are used for the jewelling of watches.Magnetite, or Magnetic Iron-ore (10f), the richest ore of Iron, of which it contains 72 per cent., is the natural magnet.Uraninite, or Pitchblende (10h), consists mainly of Uranium and Oxygen, but contains traces of Helium and Radium, of which latter it is the commercial source.Chrysoberyl (9e) is another precious stone, almost equal in lustre and hardness to the Sapphire; one variety is a beautiful greenish-yellow; another, with a peculiar play of light, is the Cat’s-eye; and a third, green by sunlight, but red by candle- or lamp-light, is known as Alexandrite.Corundum (9f), when clear and of the proper colour, is, after the Diamond, the most precious of stones. When pure, it is colourless, but with minute traces of colouring ingredient it assumes the richest and most varied hues; when red it is Ruby, and when blue Sapphire; the yellow, green, and purple varieties were at one time known respectively as the Oriental Topaz, Emerald, and Amethyst. The prefix “Oriental” was at first used to suggest that the stones are not ordinary Topaz, Emerald, and Amethyst, but other similarly colouredminerals coming from the East (India, Ceylon, Siam, Pegu, etc.); it was afterwards understood to suggest only the excellence of their characters. The Star-stone, another variety of Corundum, when placed in a strong light shows a six-rayed star.Hæmatite (11a) is a valuable ore of iron (Iron 70, Oxygen 30, per cent.).Cassiterite, or Tin-stone (11f), is the ore of Tin, of which metal it contains 79 per cent.Zircon (13b), when clear and without flaws, is one of the precious stones: one variety with peculiar red tints is the Hyacinth or Jacynth, while the colourless, yellowish, and dull green phases are termed Jargoon: the colourless variety, owing to its high refractive and dispersive power, approaches the Diamond in brilliancy.Quartz, which is Silica, the oxide of Silicon, is the most common of Minerals. In its clear and transparent variety it is the Crystal of the ancients and the Rock-Crystal of modern times; it is the Brazilian Pebble of spectacle-makers (14c). After the clear come the smoky varieties, including the Scotch Cairngorm and Occidental Topaz (14g). Next follows the Amethyst (14g), one of the less valuable, though one of the most beautiful, of gem stones. The Quartz Cat’s-eye (13f) is a variety presenting a similar play of light to that of the Chrysoberyl Cat’s-eye already referred to: the effect is due to enclosed fibres of an Asbestos-like mineral in the specimens from Ceylon, and to fibres of Crocidolite in the blue, and of altered Crocidolite in the brownish-yellow specimens from South Africa.Jasper (13g) is a coloured mixture of Silica and Clay, distinguished from ordinary Quartz by its opacity and dull earthy fracture. It is of various colours, chiefly red, brown, yellow, and green; the colours being arranged sometimes in a nodular form, as in Egyptian Jasper, at other times in stripes, as in Riband Jasper.The Lydian or Touch-stone (15a), by reason of its hardness and black colour, has been used from remote ages to test the purity of precious metals.Hornstone (15a) is a variety of Silica without evidentcrystallisation, and generally presenting a more or less splintery fracture; in one kind, Flint (15b), the surface of fracture is generally shell-shaped (conchoidal), sometimes conical, as is well shown by specimens in the case.Chalcedony (15b), which has a lustre nearly that of wax, is translucent. The specimens of Enhydros from Uruguay (15d) are of especial interest as containing imprisoned water.Heliotrope, or Bloodstone (16a), is a green stone with red, blood-like spots.Next follow the Plasma and Chrysoprase, which are green stones: and the Sard, generally brownish-red; as also the Sardonyx, its banded variety. All were much prized by the ancients because, though hard and tough enough to resist ordinary wear and tear, they are more suited to the display of the engraver’s skill than the still harder and more precious stones.Then come the Agates (16b), chiefly formed of thin layers of porous Chalcedony of different colours, though the material of many of the white layers is a compact Semi-opal. Most are now brought from Uruguay, in South America, and cut and polished at Oberstein, in Germany, where in former times Agates were collected in quantity from the mountains of the district. Sometimes the layers are parallel, and the stone is then an Onyx, useful as a material for cameos: or the bands of a section are arranged in parallel sets of zigzag lines, and the stone is then called a Fortification-agate; but in the ordinary agate the layers are variously curved. Moss-agates, or Mocha-stones (16e), are varieties of Chalcedony enclosing moss-like forms of oxides of Manganese and Iron, and green earthy Chlorite. Carnelian (16e) is a beautiful red stone much valued by the engraver: its fracture has a peculiar waxy lustre, and is distinct from that of the Sard, which is dull and horn-like.Opal, including the Precious or Noble Opal (16f), among the specimens of which is a fine suite from Queensland presented by the late Professor Story-Maskelyne, is hydrated Silica.Carbonates.Witherite, the carbonate of Barium (18a), is used in the manufacture of plate-glass. Strontianite (18b), the carbonate of Strontium, is one of two minerals from which Strontiumnitrate is made for use in the manufacture of fireworks, owing to the fine crimson colour which the salt gives to the flame: the Strontium minerals are also employed in connection with sugar-refining. Cerussite (18b) is the corresponding carbonate of Lead, and when abundant is a valuable ore of that metal.Calcite (18e), a carbonate of the metal Calcium, is represented by a fine suite of specimens, illustrating an almost endless variety of crystalline form. The clear variety from Iceland is largely used in optical instruments for polarising light. Chalybite, or Spathic Iron-ore (20h), is the carbonate of Iron, and a valuable ore of that metal. The most important English Iron-ore, Clay Ironstone, is a mixture of Chalybite and Clay. Calamine (19h), a carbonate of Zinc, is an important Zinc-ore. Chessylite (21d) and Malachite (22b) are respectively the blue and green carbonates of Copper, and are used as ores of that metal. Malachite is found in large masses; by reason of the high polish which it takes and its beautiful markings, it is much used for ornamental work of various kinds.Silicates.Passing to the Silicates, we come to Olivine (22f), one of the less hard of the precious stones; when of a yellow colour it is known as Chrysolite, while the green variety is the Peridot of jewellers. Hiddenite (23a) is a rare emerald-green variety of Spodumene, and Kunzite is a lilac-coloured variety which is used as a gem stone.Asbestos (24c), a kind of Hornblende (a mineral common in rocks of igneous origin), is found in long fibres; in some of its varieties it is so flexible that it can be woven into gloves and other articles. The term Asbestos, meaning unquenched or unquenchable, was applied by the ancient Greeks, because, owing to being unaltered by heat, wicks made of this mineral were used in maintaining the perpetual sacred fires of their temples. Napkins of Asbestos were cleaned by being thrown into the fire; Asbestos-cloth was also used in the process of cremation to keep the ashes of the body distinct from those of the fuel. It is now employed for lining iron-safes, packing for steam-pipes and boilers, and in gas-stoves, for which purposes its low conductivity for heat renders it serviceable.Jade or Nephrite (24d), a valued mineral, belongs to thesame group as Hornblende. The various shades of colour and the beautiful polish which this tough mineral will take are illustrated by specimens in the case. Several worked specimens from New Zealand and China are exhibited. An immense water-worn mass, weighing 1156 lb., found some years ago in Asiatic Russia, is mounted on a separate stand near by.Meerschaum (23g), the light soft porous mineral used for tobacco-pipes, is a hydrated silicate of Magnesium. Serpentine (25a) is another hydrated Magnesium-silicate: the ease with which it is worked and polished, its green colour, and varied markings render it much sought after as a material for mantel-pieces, tables, and other indoor work: exposed to the weather it soon loses its polish.Topaz (25c) in its clear varieties is one of the precious stones. The crystals from the Urulga river, Siberia, are remarkably fine, and of a delicate brown colour; they are kept covered, as the action of light slowly bleaches them. The yellow crystals from Brazil assume a peculiar pink colour when heated, and are then known to jewellers as Burnt or Pink Topaz. A fine orange-red crystal from Brazil is exhibited.Garnet also belongs to the group of precious stones; when the red is tinged with violet, the stone is the Almandine or Syrian Garnet (named after Syriam in Pegu), and when cuten cabochon, the Carbuncle of jewellery (26f); the Cinnamon-stone or Hessonite varies in tint from hyacinth-red to honey-yellow (26e); the Pyrope, including the “Cape Ruby” and the Bohemian garnet, is blood-red (26e), Demantoid is an emerald-green (26g).Jadeite (27a) is one of the green stones which, under the name of Jade, are wrought into ornaments in China: from jade it is distinguished by its chemical composition, structure, and higher specific gravity. Among the specimens of Epidote (27c) a remarkable series from the Untersulzbachthal, Austria, is exhibited.Mica (28a) is the name given to a group of minerals differing much from each other in chemical composition and optical properties, but having as a common character an easy splitting, orcleavage, in a single direction, and thus affording plates remarkably thin, transparent, tough, and elastic. One of these minerals, Muscovite (28d), has been used in Russia in place of glass for windows, and is now in common use for lanterns and stoves, not being so easily cracked as glass by changes of temperature; it is often known in commerce as talc, a term restricted by mineralogists to a different mineral.The group of Felspars, the most important of the rock-forming minerals, begins at case 28f. After the Felspars comes Beryl, of which the bright green variety, Emerald (29c), is one of the most valued of precious stones. It was in ancient times worked in Egypt, as is proved by specimens found in the old workings by Sir Gardner Wilkinson, and presented by him to the Museum. Emeralds occur in the Urals; but the locality for the finest stones has long been Muzo, about seventy miles from Santa Fé de Bogotá, in South America. Faceted specimens of the colourless Beryl, of the bluish-green Beryl, known in jewellery as Aquamarine, and of pink Beryl from California and Madagascar, are exhibited (30a).In cases 30f to 32d will be found examples of the Zeolite group of minerals.Tourmaline (33a), when free from flaws, is, in some of its varieties, to be classed with the precious stones; among these being a pink variety called Rubellite. Fine specimens of Rubellite from Burma, the Urals, and Madagascar, are shown in the case; one specimen from Burma, poor in colour but remarkable for its size and shape, was brought home by Colonel Symes, to whom it had been presented by the King of Ava in the year 1795. The pink-and-green tourmalines from Maine, U.S.A., and the magnificent crystals from San Diego Co., California, are among the more beautiful of the mineral products of the United States. Examples of the blue Tourmaline, or Indicolite, are shown in case 33b.A rich blue mineral, the Lapis-lazuli of jewellery (34b), brought from Persia, Siberia, Bokhara, and Chili, is a mixture of various species. When powdered, Lapis-lazuli furnished the once costly pigment ultramarine; but by the discovery of a method of producing an artificial and cheap form of the latter, the use of the mineral as a pigment has ceased.Sulphates, Phosphates, etc.The sulphates of Strontium, Celestite (35c), of Barium, Barytes or Heavy Spar (36a), and of Lead, Anglesite (36e), are all represented by series of specimens.Gypsum, or Selenite (36f), is a hydrated sulphate of the metal Calcium: when heated, it gives up its water of crystallisation and falls to a white powder, known as “Plaster of Paris,” which, when moistened, again combines with water and yields a coherent solid. Gypseous Alabaster, a massive variety of Gypsum (36h), owing to its whiteness, fine texture, and softness is used as a material for statuettes and other indoor ornaments. Oriental Alabaster is a harder substance, Stalagmitic Calcite, carbonate of Calcium.Borax (37c), a borate of Sodium, is much used as a flux, also in soldering, and in the preparation of easily fusible enamels. It was formerly carried over the Himalayas on sheep and goats from lakes in Tibet, but is now obtained largely from the Borax-lakes of the United States, and is also extensively prepared from the boracic acid lagoons in Tuscany.Nitratine or Soda-nitre (37d), found in Chili in beds of large extent, is largely used for the preparation of Nitric Acid and Saltpetre, and is also used as a fertiliser.Calaite or Turquoise (38g), a phosphate of the metals Aluminium and Copper, is generally massive; only very rarely does it occur in the crystalline state. Being as hard as Felspar and taking a good polish, it has been much prized in jewellery; that which comes into the market is chiefly brought from the Turquoise-mines not far from Nishapur, in Persia.Amber.As a supplement to the collection of simple Minerals, is arranged, in case 41, a group of natural substances which either belong or are closely related to the Mineral Kingdom, although, in the formation of most, organised matter has played a very important part. The most important of these are Coal and Amber. Coal (41a), in most of its varieties, gives structural evidence of its vegetable origin: its chemical composition depends on the amount of change which has taken place, and thus is less definite than in the preceding minerals. In the variety called Anthracite all traces of the original organised structure have disappeared. Amber (41c), in ancienttimes regarded as one of the precious stones, is likewise of vegetable origin. It is fossil resin, chiefly derived from trees allied to the pines; its originally sticky condition is proved by the insects sometimes found enclosed.Larger Mineral Specimens.In the pavilion at the east end of the gallery the visitor will find many mineral specimens which, owing to their size, cannot be satisfactorily exhibited in the table-cases.Among these, attention may be directed to the magnificent series of Minerals in the wall-cases, and to the large specimen of Gypsum, or Selenite, presented by H.R.H. the late Prince Consort, which, with some fine masses of Iceland Spar, is exhibited in a special case.Of the four table-cases in the windows of the pavilion, the first three contain a series illustrating the various kinds of Pseudomorphs, or minerals in which the original constituent has been altered and replaced by a new substance which preserves the crystalline form of the first. The fourth displays a set of specimens selected by the late Professor Ruskin to illustrate varieties of Silica.24Meteorites.The most important feature of the pavilion is the collection of Meteorites,25of which the smaller specimens are shown in the four central cases. The fall of masses of stone and iron from the sky, though observed again and again since the most remote ages, was very rarely credited by anyone beside the spectators themselves; and till the beginning of the nineteenth century no attempt was made to collect such specimens for examination and comparison. In the special guide it is shown how evidence of the actual fall of such bodies at length became irresistible, and a description is given of the circumstances attending their fall, of their general characters, and their chemical composition: illustrative specimens, collected together for easy reference, will be found in one of the cases. It is also shown that meteorites are closely related, not only to shooting stars, but also to comets, and probably to nebulæ and fixed stars.Second Floor.Botanical Gallery.The upper floor of the East wing is devoted to the Department of Botany.The Collections of this Department consist of two portions, the one open to the public and consisting of specimens suitable for exhibition, and mainly intended to illustrate the various groups of the Vegetable Kingdom and the broad facts on which the natural system of the classification of plants is based; the other set apart for the use of persons engaged in the detailed scientific study of plants.On the landing outside the gallery is a series of tree-sections representing some common British-grown trees, with sections and bark of the Cork-Oak (Quercus suber), and large sections of the White Fir and Douglas Pine from British Columbia. The Douglas Pine was cut down in 1885 when 533 years old; its age is indicated by the annual rings seen in transverse section of the wood, and a record of events has been painted on the surface. A collection of plant-abnormalities is also shown.System of Classification.The system of classification followed in the exhibition-cases in the public gallery is a modification of one widely used on the Continent and in America. In the first bay on the left-hand side an attempt has been made to illustrate, by means of books dealing with the subject, the history and development of modern systems of classification. There is aGuide26to this exhibition. The series of specimens (starting on the north, or left-hand, side of the gallery) begins with the simpler orders of Dicotyledonous Seed-plants, those in which petals are wanting in the flower or if present are free from each other, and passes on to the less simple orders with united petals. The orders are represented by dried or otherwise prepared specimens of the plants themselves, drawings, fruits, and prepared sections of the woods. Diagrams are employed to indicate the characters in the flowers on which the grouping is based. The use of thesame colour for corresponding structures throughout the diagrams readily conveys to the eye the points of agreement or difference on which the classification rests. The geological history of each natural order is indicated on a table of strata, and its present distribution on the surface of the earth given on a small map of the world. Descriptive labels afford particular information respecting each specimen.The Dicotyledonous Plants extend to the fifth case on the left side of the gallery, and are followed by the Monocotyledonous orders, which fill a portion of the last case on the same side, the two half-cases at the end of the gallery, and the first case returning towards the door. The Gymnosperms are placed in the next case. Then follow the Cryptogams, a case being devoted to the higher, vascular orders, and another to the cellular plants. The series closes with an interesting collection of models of the larger British Fungi, coloured and mounted in accordance with their natural habitats. A Catalogue of these models has been prepared.27In the table-case in the last bay is placed an illustrated collection of the British Mycetozoa, to which there is also aGuide.28A large chalk-like mass of Diatom-earth containing twelve billion Diatoms is placed in a case by itself near the entrance to the gallery. The table- and window-cases in the bays contain exhibitions of interest under the following heads: Insectivorous plants (at present in the Central Hall), Parasitic plants, Water-plants, Xerophytic plants, Epiphytic plants, Adaptations for Defence, Climbing plants, Fertilisation of flowers (also in the Hall), and Dispersal of seeds, a selection of British plants dried in sand and preserving their form and colour, and a series of Lichens from Chili. Attention may likewise be directed to a series of coloured drawings of British Plants. At the entrance of the gallery on the right is placed a camera to exhibit stereoscopic views of plants in their natural colours; and on the left is a model of a large fungus (Hydnum).At the end of the gallery the larger specimens of Palms are set up against the screen dividing the gallery from the Herbarium; other Palms, Cycads, Tree-ferns, etc., are placed in thebays next the appropriate wall-cases. Suspended from the roof is a fine specimen of the “Wabo” Bamboo (Dendrocalamus) from Burma, 81 feet long; and on the floor of the gallery are specimens of the Vegetable Sheep (Raoulia) of New Zealand, a large aërial root of a Banyan, a Brazilian Tree-lily (Vellozia), a large Bamboo from Demerara, an Australian Grass-tree (Kingia), a Brazilian Palm (Acrocomia), a Sugar-cane, and a Japanese Cycad.British Plants.A collection of British Plants is exhibited in glazed frames fastened by hinges to uprights. The classification of the Flowering Plants and Ferns is that used in Bentham’s “Handbook of the British Flora,” and descriptions are attached as labels to each plant.29Three series of frames contain specimens of the British Flowering Plants and Ferns. The fourth frame is occupied with the Mosses and Stoneworts (Characeæ), and forms the beginning of the exhibition of Cellular Plants. The series is continued in the frames on the other side of the gallery containing the lower Fungi and coloured drawings of the larger Fungi; a small series of the larger kind of Fungi found near London is also shown. In the first bay to the right on entering are series of coloured drawings (natural size) of edible and poisonous fungi, and of field and cultivated mushrooms and poisonous or worthless species often mistaken for mushrooms. AGuide30to the latter series has been prepared. The British Lichens are arranged in a cabinet of shallow glass-topped drawers.Herbarium.Above the entrance to the great Herbarium is a life-size photograph of an Orchid (Phalænopsis) from the Philippine Islands.The portion reserved for the use of the scientific student consists mainly of the great Herbarium of Flowering Plants. This is a collection of dried plants, respectively fastened on single sheets of stiff folio paper, and representing, so far as it has been possible to obtain them, every species of living plant and the distribution of each of these on the surface of the earth. The various species are collected under their respective genera, which arearranged in their natural orders; the whole being classified according to the system of Bentham and Hooker’s “Genera Plantarum.” The plants of the British Isles form a small separate collection. The important herbarium of Sir Hans Sloane is kept distinct in its original form, the plants being pasted on the pages of 333 large folios. There are other ancient herbaria of great historic and scientific interest, as well as an excellent working library and a collection of drawings of plants. The Herbarium of Vascular Cryptogams (Ferns) and Cellular Plants (Mosses, Liverworts, Algæ, Lichens, and Fungi) is in a separate room entered from the head of the great staircase.
Chlorides, etc.
III. Common Salt, the chloride of the metal Sodium, is exhibited in case 8f, and Fluor-spar, a fluoride of Calcium belonging to the same division, begins at case 7e.
Oxides.
IV. The next division consists of compounds of Oxygen and includes most of the stony Minerals.
Cuprite (10a), an important ore of Copper (Copper 89, Oxygen 11, per cent.), is at first ruby-red in colour, but becomes blackened by exposure to light.
Spinel (10e), in its transparent varieties, is one of the precious stones; the deep red being the Spinel Ruby (less dense and less hard than the true Ruby), the rose-tinted the Balas Ruby, and the yellow or orange-red the Rubicelle of the jewellers: sometimes, it has a dark blue colour. On account of their hardness, the less valuable specimens are used for the jewelling of watches.
Magnetite, or Magnetic Iron-ore (10f), the richest ore of Iron, of which it contains 72 per cent., is the natural magnet.
Uraninite, or Pitchblende (10h), consists mainly of Uranium and Oxygen, but contains traces of Helium and Radium, of which latter it is the commercial source.
Chrysoberyl (9e) is another precious stone, almost equal in lustre and hardness to the Sapphire; one variety is a beautiful greenish-yellow; another, with a peculiar play of light, is the Cat’s-eye; and a third, green by sunlight, but red by candle- or lamp-light, is known as Alexandrite.
Corundum (9f), when clear and of the proper colour, is, after the Diamond, the most precious of stones. When pure, it is colourless, but with minute traces of colouring ingredient it assumes the richest and most varied hues; when red it is Ruby, and when blue Sapphire; the yellow, green, and purple varieties were at one time known respectively as the Oriental Topaz, Emerald, and Amethyst. The prefix “Oriental” was at first used to suggest that the stones are not ordinary Topaz, Emerald, and Amethyst, but other similarly colouredminerals coming from the East (India, Ceylon, Siam, Pegu, etc.); it was afterwards understood to suggest only the excellence of their characters. The Star-stone, another variety of Corundum, when placed in a strong light shows a six-rayed star.
Hæmatite (11a) is a valuable ore of iron (Iron 70, Oxygen 30, per cent.).
Cassiterite, or Tin-stone (11f), is the ore of Tin, of which metal it contains 79 per cent.
Zircon (13b), when clear and without flaws, is one of the precious stones: one variety with peculiar red tints is the Hyacinth or Jacynth, while the colourless, yellowish, and dull green phases are termed Jargoon: the colourless variety, owing to its high refractive and dispersive power, approaches the Diamond in brilliancy.
Quartz, which is Silica, the oxide of Silicon, is the most common of Minerals. In its clear and transparent variety it is the Crystal of the ancients and the Rock-Crystal of modern times; it is the Brazilian Pebble of spectacle-makers (14c). After the clear come the smoky varieties, including the Scotch Cairngorm and Occidental Topaz (14g). Next follows the Amethyst (14g), one of the less valuable, though one of the most beautiful, of gem stones. The Quartz Cat’s-eye (13f) is a variety presenting a similar play of light to that of the Chrysoberyl Cat’s-eye already referred to: the effect is due to enclosed fibres of an Asbestos-like mineral in the specimens from Ceylon, and to fibres of Crocidolite in the blue, and of altered Crocidolite in the brownish-yellow specimens from South Africa.
Jasper (13g) is a coloured mixture of Silica and Clay, distinguished from ordinary Quartz by its opacity and dull earthy fracture. It is of various colours, chiefly red, brown, yellow, and green; the colours being arranged sometimes in a nodular form, as in Egyptian Jasper, at other times in stripes, as in Riband Jasper.
The Lydian or Touch-stone (15a), by reason of its hardness and black colour, has been used from remote ages to test the purity of precious metals.
Hornstone (15a) is a variety of Silica without evidentcrystallisation, and generally presenting a more or less splintery fracture; in one kind, Flint (15b), the surface of fracture is generally shell-shaped (conchoidal), sometimes conical, as is well shown by specimens in the case.
Chalcedony (15b), which has a lustre nearly that of wax, is translucent. The specimens of Enhydros from Uruguay (15d) are of especial interest as containing imprisoned water.
Heliotrope, or Bloodstone (16a), is a green stone with red, blood-like spots.
Next follow the Plasma and Chrysoprase, which are green stones: and the Sard, generally brownish-red; as also the Sardonyx, its banded variety. All were much prized by the ancients because, though hard and tough enough to resist ordinary wear and tear, they are more suited to the display of the engraver’s skill than the still harder and more precious stones.
Then come the Agates (16b), chiefly formed of thin layers of porous Chalcedony of different colours, though the material of many of the white layers is a compact Semi-opal. Most are now brought from Uruguay, in South America, and cut and polished at Oberstein, in Germany, where in former times Agates were collected in quantity from the mountains of the district. Sometimes the layers are parallel, and the stone is then an Onyx, useful as a material for cameos: or the bands of a section are arranged in parallel sets of zigzag lines, and the stone is then called a Fortification-agate; but in the ordinary agate the layers are variously curved. Moss-agates, or Mocha-stones (16e), are varieties of Chalcedony enclosing moss-like forms of oxides of Manganese and Iron, and green earthy Chlorite. Carnelian (16e) is a beautiful red stone much valued by the engraver: its fracture has a peculiar waxy lustre, and is distinct from that of the Sard, which is dull and horn-like.
Opal, including the Precious or Noble Opal (16f), among the specimens of which is a fine suite from Queensland presented by the late Professor Story-Maskelyne, is hydrated Silica.
Carbonates.
Witherite, the carbonate of Barium (18a), is used in the manufacture of plate-glass. Strontianite (18b), the carbonate of Strontium, is one of two minerals from which Strontiumnitrate is made for use in the manufacture of fireworks, owing to the fine crimson colour which the salt gives to the flame: the Strontium minerals are also employed in connection with sugar-refining. Cerussite (18b) is the corresponding carbonate of Lead, and when abundant is a valuable ore of that metal.
Calcite (18e), a carbonate of the metal Calcium, is represented by a fine suite of specimens, illustrating an almost endless variety of crystalline form. The clear variety from Iceland is largely used in optical instruments for polarising light. Chalybite, or Spathic Iron-ore (20h), is the carbonate of Iron, and a valuable ore of that metal. The most important English Iron-ore, Clay Ironstone, is a mixture of Chalybite and Clay. Calamine (19h), a carbonate of Zinc, is an important Zinc-ore. Chessylite (21d) and Malachite (22b) are respectively the blue and green carbonates of Copper, and are used as ores of that metal. Malachite is found in large masses; by reason of the high polish which it takes and its beautiful markings, it is much used for ornamental work of various kinds.
Silicates.
Passing to the Silicates, we come to Olivine (22f), one of the less hard of the precious stones; when of a yellow colour it is known as Chrysolite, while the green variety is the Peridot of jewellers. Hiddenite (23a) is a rare emerald-green variety of Spodumene, and Kunzite is a lilac-coloured variety which is used as a gem stone.
Asbestos (24c), a kind of Hornblende (a mineral common in rocks of igneous origin), is found in long fibres; in some of its varieties it is so flexible that it can be woven into gloves and other articles. The term Asbestos, meaning unquenched or unquenchable, was applied by the ancient Greeks, because, owing to being unaltered by heat, wicks made of this mineral were used in maintaining the perpetual sacred fires of their temples. Napkins of Asbestos were cleaned by being thrown into the fire; Asbestos-cloth was also used in the process of cremation to keep the ashes of the body distinct from those of the fuel. It is now employed for lining iron-safes, packing for steam-pipes and boilers, and in gas-stoves, for which purposes its low conductivity for heat renders it serviceable.
Jade or Nephrite (24d), a valued mineral, belongs to thesame group as Hornblende. The various shades of colour and the beautiful polish which this tough mineral will take are illustrated by specimens in the case. Several worked specimens from New Zealand and China are exhibited. An immense water-worn mass, weighing 1156 lb., found some years ago in Asiatic Russia, is mounted on a separate stand near by.
Meerschaum (23g), the light soft porous mineral used for tobacco-pipes, is a hydrated silicate of Magnesium. Serpentine (25a) is another hydrated Magnesium-silicate: the ease with which it is worked and polished, its green colour, and varied markings render it much sought after as a material for mantel-pieces, tables, and other indoor work: exposed to the weather it soon loses its polish.
Topaz (25c) in its clear varieties is one of the precious stones. The crystals from the Urulga river, Siberia, are remarkably fine, and of a delicate brown colour; they are kept covered, as the action of light slowly bleaches them. The yellow crystals from Brazil assume a peculiar pink colour when heated, and are then known to jewellers as Burnt or Pink Topaz. A fine orange-red crystal from Brazil is exhibited.
Garnet also belongs to the group of precious stones; when the red is tinged with violet, the stone is the Almandine or Syrian Garnet (named after Syriam in Pegu), and when cuten cabochon, the Carbuncle of jewellery (26f); the Cinnamon-stone or Hessonite varies in tint from hyacinth-red to honey-yellow (26e); the Pyrope, including the “Cape Ruby” and the Bohemian garnet, is blood-red (26e), Demantoid is an emerald-green (26g).
Jadeite (27a) is one of the green stones which, under the name of Jade, are wrought into ornaments in China: from jade it is distinguished by its chemical composition, structure, and higher specific gravity. Among the specimens of Epidote (27c) a remarkable series from the Untersulzbachthal, Austria, is exhibited.
Mica (28a) is the name given to a group of minerals differing much from each other in chemical composition and optical properties, but having as a common character an easy splitting, orcleavage, in a single direction, and thus affording plates remarkably thin, transparent, tough, and elastic. One of these minerals, Muscovite (28d), has been used in Russia in place of glass for windows, and is now in common use for lanterns and stoves, not being so easily cracked as glass by changes of temperature; it is often known in commerce as talc, a term restricted by mineralogists to a different mineral.
The group of Felspars, the most important of the rock-forming minerals, begins at case 28f. After the Felspars comes Beryl, of which the bright green variety, Emerald (29c), is one of the most valued of precious stones. It was in ancient times worked in Egypt, as is proved by specimens found in the old workings by Sir Gardner Wilkinson, and presented by him to the Museum. Emeralds occur in the Urals; but the locality for the finest stones has long been Muzo, about seventy miles from Santa Fé de Bogotá, in South America. Faceted specimens of the colourless Beryl, of the bluish-green Beryl, known in jewellery as Aquamarine, and of pink Beryl from California and Madagascar, are exhibited (30a).
In cases 30f to 32d will be found examples of the Zeolite group of minerals.
Tourmaline (33a), when free from flaws, is, in some of its varieties, to be classed with the precious stones; among these being a pink variety called Rubellite. Fine specimens of Rubellite from Burma, the Urals, and Madagascar, are shown in the case; one specimen from Burma, poor in colour but remarkable for its size and shape, was brought home by Colonel Symes, to whom it had been presented by the King of Ava in the year 1795. The pink-and-green tourmalines from Maine, U.S.A., and the magnificent crystals from San Diego Co., California, are among the more beautiful of the mineral products of the United States. Examples of the blue Tourmaline, or Indicolite, are shown in case 33b.
A rich blue mineral, the Lapis-lazuli of jewellery (34b), brought from Persia, Siberia, Bokhara, and Chili, is a mixture of various species. When powdered, Lapis-lazuli furnished the once costly pigment ultramarine; but by the discovery of a method of producing an artificial and cheap form of the latter, the use of the mineral as a pigment has ceased.
Sulphates, Phosphates, etc.
The sulphates of Strontium, Celestite (35c), of Barium, Barytes or Heavy Spar (36a), and of Lead, Anglesite (36e), are all represented by series of specimens.
Gypsum, or Selenite (36f), is a hydrated sulphate of the metal Calcium: when heated, it gives up its water of crystallisation and falls to a white powder, known as “Plaster of Paris,” which, when moistened, again combines with water and yields a coherent solid. Gypseous Alabaster, a massive variety of Gypsum (36h), owing to its whiteness, fine texture, and softness is used as a material for statuettes and other indoor ornaments. Oriental Alabaster is a harder substance, Stalagmitic Calcite, carbonate of Calcium.
Borax (37c), a borate of Sodium, is much used as a flux, also in soldering, and in the preparation of easily fusible enamels. It was formerly carried over the Himalayas on sheep and goats from lakes in Tibet, but is now obtained largely from the Borax-lakes of the United States, and is also extensively prepared from the boracic acid lagoons in Tuscany.
Nitratine or Soda-nitre (37d), found in Chili in beds of large extent, is largely used for the preparation of Nitric Acid and Saltpetre, and is also used as a fertiliser.
Calaite or Turquoise (38g), a phosphate of the metals Aluminium and Copper, is generally massive; only very rarely does it occur in the crystalline state. Being as hard as Felspar and taking a good polish, it has been much prized in jewellery; that which comes into the market is chiefly brought from the Turquoise-mines not far from Nishapur, in Persia.
Amber.
As a supplement to the collection of simple Minerals, is arranged, in case 41, a group of natural substances which either belong or are closely related to the Mineral Kingdom, although, in the formation of most, organised matter has played a very important part. The most important of these are Coal and Amber. Coal (41a), in most of its varieties, gives structural evidence of its vegetable origin: its chemical composition depends on the amount of change which has taken place, and thus is less definite than in the preceding minerals. In the variety called Anthracite all traces of the original organised structure have disappeared. Amber (41c), in ancienttimes regarded as one of the precious stones, is likewise of vegetable origin. It is fossil resin, chiefly derived from trees allied to the pines; its originally sticky condition is proved by the insects sometimes found enclosed.
Larger Mineral Specimens.
In the pavilion at the east end of the gallery the visitor will find many mineral specimens which, owing to their size, cannot be satisfactorily exhibited in the table-cases.
Among these, attention may be directed to the magnificent series of Minerals in the wall-cases, and to the large specimen of Gypsum, or Selenite, presented by H.R.H. the late Prince Consort, which, with some fine masses of Iceland Spar, is exhibited in a special case.
Of the four table-cases in the windows of the pavilion, the first three contain a series illustrating the various kinds of Pseudomorphs, or minerals in which the original constituent has been altered and replaced by a new substance which preserves the crystalline form of the first. The fourth displays a set of specimens selected by the late Professor Ruskin to illustrate varieties of Silica.24
Meteorites.
The most important feature of the pavilion is the collection of Meteorites,25of which the smaller specimens are shown in the four central cases. The fall of masses of stone and iron from the sky, though observed again and again since the most remote ages, was very rarely credited by anyone beside the spectators themselves; and till the beginning of the nineteenth century no attempt was made to collect such specimens for examination and comparison. In the special guide it is shown how evidence of the actual fall of such bodies at length became irresistible, and a description is given of the circumstances attending their fall, of their general characters, and their chemical composition: illustrative specimens, collected together for easy reference, will be found in one of the cases. It is also shown that meteorites are closely related, not only to shooting stars, but also to comets, and probably to nebulæ and fixed stars.
Botanical Gallery.
The upper floor of the East wing is devoted to the Department of Botany.
The Collections of this Department consist of two portions, the one open to the public and consisting of specimens suitable for exhibition, and mainly intended to illustrate the various groups of the Vegetable Kingdom and the broad facts on which the natural system of the classification of plants is based; the other set apart for the use of persons engaged in the detailed scientific study of plants.
On the landing outside the gallery is a series of tree-sections representing some common British-grown trees, with sections and bark of the Cork-Oak (Quercus suber), and large sections of the White Fir and Douglas Pine from British Columbia. The Douglas Pine was cut down in 1885 when 533 years old; its age is indicated by the annual rings seen in transverse section of the wood, and a record of events has been painted on the surface. A collection of plant-abnormalities is also shown.
System of Classification.
The system of classification followed in the exhibition-cases in the public gallery is a modification of one widely used on the Continent and in America. In the first bay on the left-hand side an attempt has been made to illustrate, by means of books dealing with the subject, the history and development of modern systems of classification. There is aGuide26to this exhibition. The series of specimens (starting on the north, or left-hand, side of the gallery) begins with the simpler orders of Dicotyledonous Seed-plants, those in which petals are wanting in the flower or if present are free from each other, and passes on to the less simple orders with united petals. The orders are represented by dried or otherwise prepared specimens of the plants themselves, drawings, fruits, and prepared sections of the woods. Diagrams are employed to indicate the characters in the flowers on which the grouping is based. The use of thesame colour for corresponding structures throughout the diagrams readily conveys to the eye the points of agreement or difference on which the classification rests. The geological history of each natural order is indicated on a table of strata, and its present distribution on the surface of the earth given on a small map of the world. Descriptive labels afford particular information respecting each specimen.
The Dicotyledonous Plants extend to the fifth case on the left side of the gallery, and are followed by the Monocotyledonous orders, which fill a portion of the last case on the same side, the two half-cases at the end of the gallery, and the first case returning towards the door. The Gymnosperms are placed in the next case. Then follow the Cryptogams, a case being devoted to the higher, vascular orders, and another to the cellular plants. The series closes with an interesting collection of models of the larger British Fungi, coloured and mounted in accordance with their natural habitats. A Catalogue of these models has been prepared.27In the table-case in the last bay is placed an illustrated collection of the British Mycetozoa, to which there is also aGuide.28A large chalk-like mass of Diatom-earth containing twelve billion Diatoms is placed in a case by itself near the entrance to the gallery. The table- and window-cases in the bays contain exhibitions of interest under the following heads: Insectivorous plants (at present in the Central Hall), Parasitic plants, Water-plants, Xerophytic plants, Epiphytic plants, Adaptations for Defence, Climbing plants, Fertilisation of flowers (also in the Hall), and Dispersal of seeds, a selection of British plants dried in sand and preserving their form and colour, and a series of Lichens from Chili. Attention may likewise be directed to a series of coloured drawings of British Plants. At the entrance of the gallery on the right is placed a camera to exhibit stereoscopic views of plants in their natural colours; and on the left is a model of a large fungus (Hydnum).
At the end of the gallery the larger specimens of Palms are set up against the screen dividing the gallery from the Herbarium; other Palms, Cycads, Tree-ferns, etc., are placed in thebays next the appropriate wall-cases. Suspended from the roof is a fine specimen of the “Wabo” Bamboo (Dendrocalamus) from Burma, 81 feet long; and on the floor of the gallery are specimens of the Vegetable Sheep (Raoulia) of New Zealand, a large aërial root of a Banyan, a Brazilian Tree-lily (Vellozia), a large Bamboo from Demerara, an Australian Grass-tree (Kingia), a Brazilian Palm (Acrocomia), a Sugar-cane, and a Japanese Cycad.
British Plants.
A collection of British Plants is exhibited in glazed frames fastened by hinges to uprights. The classification of the Flowering Plants and Ferns is that used in Bentham’s “Handbook of the British Flora,” and descriptions are attached as labels to each plant.29Three series of frames contain specimens of the British Flowering Plants and Ferns. The fourth frame is occupied with the Mosses and Stoneworts (Characeæ), and forms the beginning of the exhibition of Cellular Plants. The series is continued in the frames on the other side of the gallery containing the lower Fungi and coloured drawings of the larger Fungi; a small series of the larger kind of Fungi found near London is also shown. In the first bay to the right on entering are series of coloured drawings (natural size) of edible and poisonous fungi, and of field and cultivated mushrooms and poisonous or worthless species often mistaken for mushrooms. AGuide30to the latter series has been prepared. The British Lichens are arranged in a cabinet of shallow glass-topped drawers.
Herbarium.
Above the entrance to the great Herbarium is a life-size photograph of an Orchid (Phalænopsis) from the Philippine Islands.
The portion reserved for the use of the scientific student consists mainly of the great Herbarium of Flowering Plants. This is a collection of dried plants, respectively fastened on single sheets of stiff folio paper, and representing, so far as it has been possible to obtain them, every species of living plant and the distribution of each of these on the surface of the earth. The various species are collected under their respective genera, which arearranged in their natural orders; the whole being classified according to the system of Bentham and Hooker’s “Genera Plantarum.” The plants of the British Isles form a small separate collection. The important herbarium of Sir Hans Sloane is kept distinct in its original form, the plants being pasted on the pages of 333 large folios. There are other ancient herbaria of great historic and scientific interest, as well as an excellent working library and a collection of drawings of plants. The Herbarium of Vascular Cryptogams (Ferns) and Cellular Plants (Mosses, Liverworts, Algæ, Lichens, and Fungi) is in a separate room entered from the head of the great staircase.