ble of tanning leather like nut-galls, oak-bark, &c., is termed ARTIFICIAL TANNIN. EXTRACT, or the ́extractive substance, is that substance which is obtained in the residuum of evaporated vegetable infusions or decoctions, and separated from jelly, gum, &c.-The extracts of different vegetable substances differ considerably from each other; but at the same time agree in possessing a slight degree of acidity, and, when liquefied, of yielding a precipitate, if mixed with ammonia.---The NARCOTIC PRINCIPLE: Several plants possess the power of occasioning sleep, and others even of thus causing death. This property exists in the most considerable degree in opium, which is yielded by the white poppy, papaver album. By appropriate processes a substance is obtained from opium, which is supposed to be the narcotic principle. It is white, crystallizes in rectangular prisms, has neither taste nor smell, and possesses several peculiar chemical properties. Its right to be considered as the narcotic principle, is evinced by its possessing the soporific qualities of the opium itself. OILS, both fixed and volatile, are found abundantly in plants. The fixed oils are found in the seeds of cotyledonous plants: it is most commonly obtained from the almond, and the olive, and from rape-seed and linseed. The volatile oils are found in almost all the different parts of plants, particularly of those which yield a peculiar odour, such as lavender, mint, roses, &c. WAX may be considered as a vegetable production, since it has been

ascertained that the varnish with which the upper side of the leaves of many trees are covered possesses all the properties of bees-wax, which is prepared by the bees from honey or sugar. Bees-wax is of a yellow colour, and of a peculiar odour; but on being duly exposed to the atmosphere, it loses both its colour and its peculiar smell, and is then the white-wax of the shops. CAMPHOR is obtained by distillation from the wood of a tree named laurus 'camphora. Camphor has been found in several other plants, and, by saturating oil of turpentine with muriatic acid gas, a substance in crystals is obtained, which, from the properties it possesses, has been named artificial camphor. BIRD-LIME: This strongly tenacious and adhesive substance appears to be chiefly formed by that substance to which the name, bird-lime, may be given, as denoting this peculiar principle. It is not soluble in water, but combines readily with oils, and does not enter into combinations with alkalies. It possesses also many other chemical properties which distinguish it from other vegetable substances. It is yielded spontaneously by the epidermis of a plant termed robinia viscosa: and is artificially procured from the middle bark of the holly, by fermentation, washing, &c. CAOUTCHOUC, so remarkable for its elasticity, and so generally used for the removal of pencil and even other markings from paper, exudes from some species of hævea and jatropha, trees growing in South America, and is said to be also produced by several trees in the East

Indies. It is insoluble in water; but dissolves in the volatile oils, which, on separation, leave it in a glutinous state. On the contrary, ether and rectified petroleum dissolve it, and leave it unaltered. RESINS

are solid, brittle substances; mostly of a yellowish colour, and possessing some degree of transparency. Their taste is rather acrid; they melt with heat, and, if fired, emit a strong yellow flame with much smoke. They exude from various trees, and differ considerably from each other according to the tree from which they proceeded. Thus we have rosin, turpentine, mastich, elemi, tacamahac, animi, &c. Copal differs in many respects from the preceding. Its solution is a most beautiful varnish. LAC is deposited on different trees of East India, by an insect called chermes lacca. When this substance is adherent to the twigs on which it has been formed, it is called stick-lac; when detached, seed-lac; and when melted and disposed in a thin crust, it is termed shell-lac. It is used for sealing wax, and for the purposes of varnish. GUM RESINS, myrrh, galbanum, olibanum, &c., are actually combinations of gum and resin. They are chiefly used in medicine. They have some_ what of a fatty appearance, are not so combustible as resins, nor do they melt so readily. CoTTON, which is that soft downy substance which envelopes the seeds of various plants, is chiefly obtained from a species of gossipium. CORK is the outer bark of the quercus suber, or cork-tree, and differs in many respects from other vegetable substances.

WOOD is chiefly formed by that part of vegetables which is termed the woody fibre, and which exists also in the leaves, the capsules of fruits, and even in some of the more delicate parts of vegetables.

Oxygen, carbon, and hydrogen, are the principles generally found in plants, with the fixed alkalies, some of the metals, and the earths, lime, magnesia, alumina and silica: the latter is supposed to form the largest part of the epidermis of some of the canes. Vegetable substances, subjected to FERMENTATION, produce, under different circumstances, either WINE, from which ALCHOL may be obtained, or the ACETIC ACID, termed vinegar. Besides which, the following acids may be obtained from vegetables, and which can be here only enumerated: Benzoic, citric, gallic, malic, oxalic, phosphoric, prussic, tartaric, &c.

BITUMENS are certain bodies, which have considerable resemblance to resins and oils, and which are found in subterraneous situations. From the examination of these bodies, it appears that they are of vegetable origin.

They sometimes occur in a fluid state, resembling the volatile oils. NAPHTHA is a yellow and transparent fluid, volatile, strongly smelling, and very light. PETROLEUM resembles naphtha, except in colour, it being of a darkish brown, probably from the deposition of carbon. Bituminous substances exist also in every degree almost of solidity: when acquiring a small degree of thickness, it is termed mineral

tar, maltha, and mineral caoutchouc; and when still harder, it is called asphaltum. In Devonshire a substance is found which accompanies the bovey coal, which Mr. Hatchett has ascertained to be composed of resin 55, asphaltum 41, and earth 3; and has named it retinasphaltum. JET is also a bituminous substance, holding much carbon. Cannel coal is of the same class, but contains more earth. Common coal has its bituminous constituent intersected by plates of carbonate of lime and sulphuret of iron.

The Animal Kingdom.

Animal substances, although containing some of the same principles found in the vegetable kingdom, still manifest considerable differences in their respective analyses. As we have already done in the vegetable kingdom, so we shall here, in the first place, take a view of those substances which enter into the composition of different animal substances, and then enter into the consideration of some of these individually.

GELATINE; jelly, employed in the arts as glue, is abundantly obtained from the skin of animals. It is soluble in water, and is precipitated therefrom, by the addition of tannin, in a substance composed of tannin and gelatin; as has been already noticed, when speaking of tannin.

ALBUMEN, as has been already observed, is that substance which forms what is termed the white of