proportion of animal matter; nay, there is reason to assume that phosphorus is formed in the animal body itself by the action of the secretory organs. We have the proof of a multitude of changes as great as this, produced under the influence of the unknown forces which we term Vital. The changes produced in the blood, under the marvellous and hidden chemistry by which this fluid is made to yield bone, muscle, fat, gastric juice, and all the other products of the animal system, are produced by such actions; and there is nothing unreasonable in the assumption, that phosphorus, a substance essential to the formation of the entire system of bones, is formed by those actions of secretion and assimilation by which the muscular and other parts of the system are built

up.

Ammonia is a constant product of the putrefaction of animal bodies; but ammonia, we shall find in the sequel, has strong points of resemblance to phosphoretted hydrogen. Now, ammonia consists of hydrogen and nitrogen, or the elements of nitrogen; and therefore we may believe that phosphorus consists of hydrogen and nitrogen, or the elements of nitrogen. Phosphorus will be seen from the table to be resolvable into H C OH N, while ammonia may be represented by H3, CO, H3 N.

=

The property of emitting light is possessed by phosphorus in a high degree; but innumerable animals possess the property of emitting light, frequently so vivid, that the smallest objects can be seen by it in the dark. The glow-worm is a familiar instance in our own climates; but the fire-flies, as they are popularly termed, of the warmer regions, emit a light so brilliant, that they may be employed in place of lamps; and the whole atmosphere is frequently illuminated by them. Many fishes too, perhaps all fishes, possess in a greater or less degree this property, and, in an eminent de

gree, the mollusca, and innumerable tribes which inhabit water. The whole ocean, so far as the eye can reach, is often seen in a blaze of light from the phosphorescence of myriads of microscopic creatures, when they approach the surface. But doubtless, the inhabitants of the ocean, every drop of which seems to be filled with living creatures, possess and exercise this marvellous function at the greatest depths, and are thus provided with the faculty of supplying themselves with light, where the rays of the sun cannot reach. Now, we cannot certainly say that the matter which yields these amazing supplies of light is phosphorus, although it is in a high degree probable that it is really phosphorus, or some analogous compound; for it can be separated from the animals, and diffused through liquids, producing phosphorescence. We have, therefore, reason to believe it to be a substance produced by the action of the animal organs; and what so reasonable a supposition as that the basis of this substance is that which enters into the composition of every animal product, whether in the land or water,-nitrogen?

Phosphorescence is not only produced by living animals, but by dead animal matter in a state of incipient decay, as we may see upon every sea-coast where fishes are cast on shore by the waves. The addition of a little nitre, or even common salt, frequently produces or increases the phosphorescence. Even decaying plants emit phosphorescent light, but feebly and rarely, because in plants nitrogen exists in a comparatively minute quantity.

Sulphur, phosphorus, and chlorine, are represented in the table respectively by CO+H2, by CO+H, and 2 CO+H2, exhibiting a derivation from a common root, and a similarity of composition, which may account for a similarity of properties. If we represent CO in these formulæ by its

equivalent N, we have, as the composition of the three bodies mentioned, respectively H2 N, H N, H7 No.

We might wonder how, in the ocean, such vast supplies of phosphorus, or compounds analogous to phosphorus, are generated, did we not admit, that all the elements forming it are contained in sea-water. Hydrogen and oxygen constitute the water of the ocean itself; while chlorine, in combination with sodium, containing the same elements as phosphorus, is in contact with every particle of water which the ocean contains.

But if we can conceive the production of nitrogen in the waters of the ocean, it is a slight difficulty to conceive the production of phosphorus. Now, whence is derived that vast supply of nitrogen, of which the muscular substance of all aquatic, as well as land animals, consists? The quantity of nitrogen which water absorbs at the surface is utterly insignificant, and cannot in the slightest degree account for the supply required for that mass of living beings with which the whole body of the ocean seems to be filled. But if we resort to the supposition, that water itself, which probably furnishes the only food of the lower aquatic tribes, and even of many of the higher, contains the elements of nitrogen, we are freed from a difficulty which no other hypothesis resolves. Now water consists of HO; and O, by our hypothesis, is resolvable into H2 C, so that water contains all the elements of nitrogen; and we have only to suppose its resolution into these elements, by the secretory and assimilating organs of animals, to conceive the production of nitrogen in a quantity which calculation cannot reach.

XIII. ARSENIC.

Arsenic occurs sometimes native, but more often in combination with other metals, and especially cobalt and nickel. On heating these ores of arsenic in a reverberatory furnace, the metal, which is very volatile, is driven off, and, combining with oxygen as it rises in the furnace flues, is condensed into cakes, which, being purified by a second sublimation, yield the arsenic of commerce. The arsenic of commerce, or white oxide of arsenic, is arsenious acid, being a combination of 2 equivalents of arsenic and 3 of oxygen, from which the metal is easily obtained by de-oxidation.

Arsenic has a crystalline texture, and a bright metallic lustre, resembling steel. It is exceedingly brittle, and may be reduced by trituration to fine powder. Its specific gravity is from 5.7 to 5.9. When exposed to heat, it sublimes at the temperature of 365° F., without being liquefied. In close vessels it volatilizes unchanged; but, if atmospheric air be present, it is converted into arsenious acid, by combining with the oxygen of the air. If thrown on a red-hot iron, it burns with a blue flame and white smoke, having the strong odour of garlic, proper to the other bodies of the class. When sublimed, it crystallizes in rhombohedral crystals, being isomorphous with tellurium and antimony.

The combining weight of arsenic is estimated by Berzelius at 37.67, by others at 75.34.

It combines with other bodies in a manner analogous to phosphorus, which it greatly resembles. It combines likewise with the metals, forming alloys, to which it generally communicates the property of brittleness. It combines with hydrogen, forming, in one proportion, a solid, and in another, in which are three equivalents of hydrogen, a very poisonous gas.

XIV. ANTIMONY.

This metal occurs native, but is chiefly derived from one of its ores, the sulphuret, from which it may be obtained, either by heating the sulphuret along with iron filings in a covered crucible, in which case the sulphur combines with iron, or by throwing it in small portions into a red-hot crucible, with substances which yield oxygen to the sulphur, and carry it off as sulphurous acid. In either case, the melted antimony collects in the bottom of the crucible, and may be drawn off and received in moulds, when it is further purified for chemical purposes.

The metal thus obtained is of a silvery colour, and of a bright metallic lustre. It is exceedingly brittle, and may be readily reduced to powder. Its specific gravity is from 6.7 to 6.8. It fuses at the temperature of about 797° F., and in cooling acquires a lamellated structure, and, when it crystallizes, assumes the rhombohedral form proper to tellurium and arsenic. It may be sublimed, at a high temperature, but, when heated in the open air, it takes fire at a red heat, emitting copious fumes of oxide of antimony. When heated to whiteness by the blow-pipe, and thrown upon any hard surface, it burns for a time with great splendour, rolling about. It combines with other substances in the manner of arsenic. Its combining weight is calculated at 64.62. Its probable composition is denoted in the table, by 4 CO+H8.

Nitrogen, phosphorus, arsenic, and antimony, then, manifest an intimate relation with one another. Their analogous compounds are similar in their crystalline forms. They all combine with 3 equivalents of hydrogen, forming respectively the three gaseous compounds, ammonia, phosphoretted