Div. IV. are orthorhombic in their forms and include Tephroite, di-manganous silicate; Fayalite, di-ferrous silicate; with Olivine and Hyalosiderite, which are the magnesium and magnesio-ferrous silicates of the series. The Chrysolite is the name of the pale yellow gem into which the larger and clearer specimens of Olivine are occasionally cut; while the Peridot is a pistachio-green variety, of which fine crystals and cut specimens are exhibited in Case 36. Gadolinite is di-yttrious silicate (containing also cerium, &c.); and Humite, a mineral containing Fluorine, belongs also to the more basic silicates.

Cases 36

Among the mono-silicates are arranged the large series of im(ii.) to 38. portant minerals which form the two parallel groups of the Augites and the Hornblendes. In juxtaposition with these is seen WollasCase 38 (ii.) tonite, the calcium monosilicate, and the anorthic minerals Rhodonite and Babingtonite, homotypic in composition, but crystallographically differing from the other members of the series. The Augitic and Hornblendic groups present two distinct crystallographic types. In Case 36 (ii.) Enstatite, the magnesian, as in Bronzite a magnesio-ferrous monosilicate crystallises in the orthorhombic system, though with certain of the angles of an Augite; while in Diopside, and the other Augites, clinorhombic in crystallisation, part of the Magnesium is displaced by Case 38 (i.) Calcium, and also by Iron, Manganese, or Zinc. So Anthophyllite, a magnesio-ferrous monosilicate, corresponding with Bronzite, presents orthorhombic forms with angles belonging to the type of the Hornblendes, as exemplified in Tremolite and the other members of the Case 38 (ii.) group, which, however, crystallise, in the oblique system. Certain varieties of Jade or Nephrite are assigned to these groups, as are also different kinds of Asbestos.

Cases 39 and 40.

The hydrated section of this series contains the Serpentines and the talcose minerals. It comprises, also, Dioptase and Chrysocolla, cupric Case 40(ii) silicate hydrates; Hemimorphite, the zinc silicate hydrate; and Apophyllite, a hydrated calcio-potassium silicate, extraordinarily fine specimens of which are seen in Case 39, and in the glazed fronts of Cases 11 and 12.

The second series in the class of the silicates consists of those of the epideutoxides (sesqui-oxides). Foremost among them is the Topaz, an aluminium silicate, in which part of the silicate is replaced by an Case 41 (i.) analogous fluosilicate. The specimens of this mineral from the Ourulga river in Siberia, collected by Col. de Kokscharow, are singularly fine. They are of a delicate sherry-colour, but are preserved in the dark, as light speedily bleaches them.

Case 42.

The third series of the silicates is constituted of those in which the monoxides and epideutoxides are associated in the same mineral.

The various groups known by the general names of the Garnets, Scapolites, Idocrase, Epidote, the Felspars, the Micas, and Dichroite (with a variety of minerals resulting from its alteration,) find their places in this series, into the hydrated section of which fall the beautiful and extensive varieties of Zeolites and Chlorites.

Among these the Garnets form a group of minerals belonging to the cubic system in which the chemical type (RR Si) remains constant,

while the isomorphous elements under that type replace each other in Div. IV. unlimited variety. Among the familiar forms of this mineral group, the violet-tinted Almandine, and the rich red Syriam Garnet, are ferrousaluminic varieties; the yellow and hyacinthine Garnets, known as Cinnamon-stone and Essonite contain calcium and aluminium : the calcium is substituted by magnesium in the deep blood-red Bohemian Garnet and Pyrope, varieties which when cut en cabochon, i.e., with a concavo-convex, or with a convex form, are the Carbuncle of jewellery. Idocrase, a mineral with a smaller range of chemical variation than the Garnet, is represented by a series of crystals (of pyramidal forms) of remarkable variety and perfection. Epidote is also well represented Case 42. by specimens from Ala and from the Obersulzbachthal. To the Case 44. Epidote group also belong the minerals Allanite, Zoisite, and Jadeite. To these succeed the various minerals, Phlogopite, Biotite, Musco- Cases 44 vite, Lepidolite, &c., included in a group under the name of Mica. and 45. Case 43 (ii.) The group of Felspars follows, among which will be found Labradorite, with its beautiful play of colours; the Moonstone, a partially decomposed Orthoclase; and a fine specimen of the Orthoclase called Case 46 (i.) "Valencianite" from Mexico. Dichroite (the Sapphire d'Eau of jewellers), is remarkable for its pleiochroism, a character due to the different degrees to which the crystal absorbs the light of different colours according to the planes of their vibration; the crystal when looked through perpendicularly to the basal face 001 is of a rich blue, perpendicularly to the faces 010 and 100 it is of a bluish white, and of a pale straw colour respectively. The Beryl includes the Emerald, and also the Aquamarine of the jewellers, and with Euclase occupies half of Case 46. It is an alumino-glucinum silicate, the Aluminium being in the Emerald apparently displaced to a minute amount by Chromium. Euclase is a mineral composed of the same elements, and containing a small quantity of water: the specimens of it from Siberia are of high interest. These are followed by hydrated silicates, in- Cases 47 to cluding a very complete collection of the Zeolites, among which the 49. Natrolite from India, the Scolecite from Iceland and India, and the Edingtonite from Scotland are remarkable.

The silicates proper are succeeded, in Case 50, by minerals in which Case 50. silicates are associated with boric-oxide or borates. Among these the Tourmalines present a rich assortment of valuable and beautiful specimens, conspicuous for crystals of Rubellite, from Siberia and Ava. Two very fine specimens of the Rubellite from the latter country are seen in this Case. The one remarkable for its magnitude and form was brought from Ava by Colonel Symes, to whom it was a present from the King of Ava. The other, also a very large specimen, and of deep colour, was presented in 1869 by C. S. J. L. Guthrie, Esq. These are succeeded, in Case 51, by a class of minerals of great mineralogical interest, containing some of the rarest of the elements, and themselves of rarity; much uncertainty, however, still attaches to the chemical formulæ of several of these species. The Case 51. titanates, the tantalates, and niobates, and these combined with silicates zirconates, and stannates, thus link the silicates to the molybdates Case 52.

Cases 51 and 52.

Div. IV. and tungstates, and these, in turn, are followed by the class of chromates and the sulphates. The suite of specimens of Perofskite from Siberia, the crystals of Eudyalite, of Columbite, of Fergusonite, and the specimens of Tscheffkinite, are especially observable for their excellence or their rarity.

Cases 53 to

55.

Case 57.

Cases 56 to

60.

Case 60.

Among the anhydrous species in the sulphates, attention may be called to the specimens of Celestine (strontium sulphate) from near Bristol, and to the Anglesite (lead sulphate) from Pennsylvania and from Monte Poni. Gypsum, or Selenite, the hydrated calcium sulphate, is an important mineral as yielding Plaster of Paris by the expulsion of its water. A magnificent specimen of this mineral, as remarkable for its size as for the grouping of its crystals, presented by His Royal Highness the late Prince Consort, ornaments a window in Room II. It was found at Reinhard's-brunn, Saxe-Coburg.

rest.

Adjoining these are a few minerals of the greatest rarity and inteThe crystals of Linarite are unique, and the specimens of Caledonite and Lanarkite, of Leadhillite, a lead hypotetracarbonate combined with sulphate, and of the rare mineral Connellite, are among the finest known of these British species.

The borates and the class of nitrates occupy part of Case 56; and thence to Case 60, the Cases are occupied by the class which includes the phosphates and arsenates, in which the isomorphism of the corresponding compounds of the arsenoid element Phosphorus, and of Arsenic, is so complete that the salts of their acids cannot be well classified apart from each other. With these also the Vanadates find their place, as being isomorphous with them.

Here may be seen fine crystals of Erythrine, the beautiful cobalt arsenate; specimens of Haidingerite (Case 57), and of Erinite (Case 57); crystals of Lazulite (Case 58); very fine suites of Uranite (phosphate of Copper and Uranium), and of Autunite; the beautiful blue Cornish mineral Liroconite; and splendid specimens of Apatite, Mimetesite, and Pyromorphite.

As an Appendix to the Collection, two half Table-Cases in Room I., contain certain organic compounds, which as occurring in the earth with constant and definite characters, independent of organic structure, find their place in a Mineral Collection. Among these, Amber, in ancient times ranking in value with the gems, is here exhibited in a large series of specimens.

In Room II. will be seen two half Table-Cases adjoining the wall, in which is arranged an extensive and instructive series of pseudomorphous minerals. They illustrate the decomposing influences to which many minerals have been subjected, and they throw valuable light on the order of succession in which, and the conditions under which, particular minerals have been formed and deposited.

NEVIL STORY-MASKELYNE.

DEPARTMENT OF BOTANY.

THE series of specimens selected from the Botanical Collections for exhibition consists chiefly of fruits, stems, and such vegetable structures as cannot from their size and texture be incorporated with the Herbarium (or collection of dried and mounted specimens), but are capable of being advanta geously exhibited. They are arranged in two rooms on the upper floor of the Museum (Nos. 17 and 18 on the plan) which are entered by a doorway on the Eastern side of the Central Zoological Saloon.

The specimens exhibited are arranged, as far as possible, in accordance with their natural affinities, beginning with the most lowly organised members.

A small collection placed in the Table Cases of the central avenue of the First Room exhibits by specimens the principal characters which distinguish the great divisions of the vegetable kingdom, and at the same time supplies a key to the main body of the collection. The Cases on the left side of the avenue (A to D are devoted to the Cryptogams or Flowerless Plants. The Fungi occupy the first Case next the entrance, and are followed in succession by the Sea-weeds (Alga), Lichens, Mosses, Liverworts (Hepatica), Ferns, Clubmosses, and Horsetails. The Cases on the right side (E to H) illustrate the Phanerogams or Flowering Plants, which are divided into Monocotyledons, Gymnosperms, and Dicotyledons. Each case contains a reference to the Wall or Table Cases where the more extensive series of specimens are exhibited.

The main series is arranged in order along the Wall Cases, beginning with that on the left on entering the First Room, continued along the left side of both rooms, and returning along the right side. This order is indicated by the numbers painted on the Cases. With one or two exceptions, the Table Cases are supplementary to the Wall Cases, the specimens in

the one further illustrating the groups in that to which they are opposite.

FUNGI. This class of cellular cryptogams is illustrated in Cases 1 to 4 by a series of models principally prepared by James Sowerby while engaged in the publication of his "Figures of English Fungi,' and representing for the most part the identical subjects depicted in that work. They are arranged and named according to Cooke's "Handbook of Eritish Fungi." The first two Cases contain the gillbearing forms (Agaricini), to which the common mushroom belongs; the third Case is chiefly filled with the Polyporei, the fruiting surface of which is composed of pores or tubes; among these may be noted the edible Boletus edulis, and the dry-rot, Merulius lacrymans; the shelves of the lower division contain Clavarias and gelatinous Tremellas; on the upper shelves of the fourth Case are placed specimens of the stinking Phalloidei, star-shaped Geasters, and puff-balls or Lycoperdons; some of the smaller sporidiiferous fungi are placed on the other shelves of this Case, among which the Truffles (Tuber) may be noted.

ALGE. The most remarkable sea-weed exhibited in Case 5 is the large tree-like Lessonia, which forms extensive submarine forests in the Patagonian seas. The stem increases in thickness by the addition of external concentric layers, giving it to the eye the appearance of exogenous wood. The Durvillea, placed near it, is an inhabitant of the same seas; it has rope-like stems from 500 to 1,500 feet long, and its fronds are composed of enormous honeycomb-like cells. From the Cape of Good Hope come the inflated stems of the huge Ecklonia buccinalis. Some large stony coralline sea-weeds are placed on the shelves.

LICHENS. On the shelves are placed specimens of Cladonia rangiferina, the reindeer moss, Rocella tinctoria, the Orchella-weed, from which important dyes are obtained, Gyrophora umbilicaria, the Tripede-roche of Arctic voyagers, and other interesting forms.

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MOSSES. Some of the larger forms of this class are exhibited on the shelves; but the small size of the Mosses and Lichens are better fitted for the closer inspection obtained in the Table Cases, where a larger series is exhibited.

The VASCULAR CRYPTOGAMS are placed in Case 5. The Clubmosses (LYCOPODIACEE) are represented by some of the larger forms, and the Horsetails (EQUISETACEE) by fine specimens of the underground rhizomes and stems of Equisetum maximum, the largest of the British species. The Ferns (FILICES) are the most important of the vascular cryptogams. The back of the Case contains specimens of the fronds of Alsophila pinnata from Chili, and of Thyrsopteris elegans, the fertile portions of which are so constricted as to bear the globose fructification on the midrib. The longitudinal and transverse sections of fern stems placed here and in the Table Cases (3 and 4) opposite show that the stem is composed of a central cellu