the assay of metals, to discover the presence of iron; dissolved in nitric acid, it also forms the aqua regia of commerce.

Native ammonia is found in the vicinity of volcanoes, in some of the mountains of Tartary and Thibet, and in some of the Tuscan lakes. It has also been detected by Dr. Marcet in seawater. On pit coal it may also be sometimes seen in a yellowish white powder. Why is old decomposed dung comparatively useless as manure?

Because, as soon as dung begins to decompose, it throws off its volatile parts, which are the most valuable and most efficient.

Why is soot a powerful manure?

Because it possesses ammoniacal salt, empyreumatic oil, and charcoal, which is capable of being rendered soluble by the action of oxygen, or pure vital air.

Why are the stem and leaves of the beet-root valuable? Because, when dried and burned, they yield ashes so rich in alkali, that it melts easily by heat, and surpasses many of the common varieties of potassa.

SULPHUR.

Why are common pyrites roasted to obtain sulphur? Because, the fumes being received into a long chamber of brickwork, the sulphur is gradually deposited; it is then purified by fusion, and cast into sticks.

Why will a roll of sulphur, when suddenly seized in a warm hand, crackle, and sometimes fall in pieces? Because the action of heat is unequal, the sulphur conducting it but slowly, and having little power cohesion.

of

Sulphur is one of the few elements which occur in nature in their simple form. It is a well known mineral substance, found in large quantities in the neighbourhood of volcanoes, and as an article of commerce is chiefly brought from the Mediterranean. The effects

It is readily

of heat upon sulphur are very curious. melted and volatilized, and begins to evaporate at 170°, and to fuse at 105°. At 220° it becomes completely fluid; between 226° and 228° it begins to crystallize; between 230° and 284° it is as liquid as clear varnish, and of an amber colour; at about 320° it begins to thicken, and acquire a red colour, and on increasing the heat, it becomes so thick that it will not pour. Between 428° and 572°, the colour is a red brown; from 572° to the boiling point it becomes thinner, but never so fluid as at 248°; the deep red brown colour continues till it boils. It sublimes (this term is used to denote the evaporation of a solid) at 600°, and condenses into the form of a powder, or, as it is termed, of flowers. When poured into water, in complete fusion, it becomes of the consistency of wax, and of a red colour; it may then be used for taking impressions from engraved stones, and hardens upon cooling. In a French Journal we read, "though it is well known that sulphur which has been recently fused does not immediately recover its former properties, no one suspected that it required whole months, and even a longer period, fully to restore it."

Why is sublimed sulphur, for delicate purposes, washed with hot water?

Because it is always slightly sour. The purity of sulphur may be estimated by gradually heating it upon a piece of platinum leaf; if free from earthy impurities, it should totally evaporate. It should also be perfectly soluble in boiling oil of turpentine.

Why is sulphuretted hydrogen of easy production? Because sulphur, in its ordinary state, always contains hydrogen, which it gives off during the action of various bodies for which it has a powerful attraction. Berzelius, by heating sulphur with oxide of lead, remarked the formation of water, but in such small and indefinite quantities, as induced him to adopt the gen

sulphuric acid. In wet spring seasons, plants flowered on this hillock sooner than on the adjoining grounds; but as soon as the spring rains began to decline, then the vegetables withered away, and appeared as if scorched. About two miles east of this place is another sulphuric acid spring, still more remarkable in one respect. The quantity of water from this spring is in sufficient quantity to turn a light grist-mill; and yet there is so much sulphuric acid present in it, that the stream will constantly redden violets, and its water coagulate milk. It is supposed that the sulphuric acid is produced in some way by the decomposition of the pyrites in the soil.-Silliman.

Cases of poisoning by sulphuric acid are not unfrequent; the best antidotes are copious draughts of chalk and water, and of carbonate of magnesia and water.— Orfila.

Why is sulphuric acid also called oil of vitriol?

Because it was formerly obtained by the distillation of green vitriol. It is now procured by burning a mixture of about 8 parts of sulphur, and of nitre, in close leaden chambers containing water, by which the fumes produced are absorbed, and by evaporation the acid is procured in a more concentrated state.-Parkes. Why should sulphuric acid always be kept closely stopped?

Because it rapidly absorbs water from the atmosphere; so that, in moist weather, 3 parts by weight increase to 4 in 24 hours.

Why is sulphuric acid important in dyeing blue? Because it instantly dissolves indigo, which, at first deep purple, becomes blue by exposure to air, or by dilution.

PHOSPHORUS.

Why is phosphorus obtainable from bone earth? Because of the phosphate of lime in bones; which,

with water and sulphuric acid, yields phosphoric acid; this, mixed with charcoal, and distilled, yields phosphoret of carbon, and this by re-distillation becomes phosphorus. Thénard is of opinion that phosphorus cannot be entirely freed from charcoal, a minute quantity of which does not impair its whiteness. Does not this illustrate its easy combustion?

Mr. Parkes notes that phosphorus was accidentally discovered at Hamburg, in 1669, by an alchemist named Brandt, in his search after gold; and two years afterwards, one Kraft brought a small piece of phosphorus to London, on purpose to show it to the king and queen of England. Mr. Boyle afterwards discovered the process, which he described in the Philosophical Transactions for 1680, and in a little book which he published in the same year, entitled the Aerial Noctiluca. Mr. Boyle instructed Mr. Godfrey Hankwitz, of London, how to procure it from urine, so that he was the first who made it for sale in England; and he continued to supply all Europe with it for many years.

Why does phosphorus shine in the air in the dark, with a pale blue light?

Because of its very slow combustion, which is attended by the production of acid: hence the necessity of preserving it in water; this has a luminous property when agitated. The combustion ceases in close vessels, as soon as the greater part of the oxygen has been absorbed. This light is caused by a white smoke; but in air perfectly dry, phosphorus does not smoke, because the acid which is formed, and closely encases the combustible, screens it from the atmospherical oxygen

In the vacuum of the air-pump, phosphorus, in small pieces loosely enveloped in cotton, will generally inflame, and burn for some time, with a pale blue light: and, in the same circumstances, it more readily kindles if sprinkled with powdered resin or sulphur; alone, it does not inflame.-Brande,

M. Osam has described, in the Bulletin Universel, several new solar phosphori, which are far more powerful than those previously known. The curious reader will find them in the Arcana of Science for 1829. See also page 53 of the present volume.

Phosphorescent phenomena are not uncommon in nature. Phosphorescent fluor spar has lately been found in Siberia and Cornwall. The luminousness of the sea, especially in stormy weather, is supposed to be a phenomenon of this class; but its cause is involved in too much controversy for place here: it was formerly believed to be caused by the electrical friction of the waves, which explanation is no longer admitted. Humboldt attributes it to certain shining molluscæ, which emit light at pleasure, and to the decomposed parts of dead medusæ, &c.* We have elsewhere cursorily noticed the properties of certain phosphorescent bodies. (See p. 52.)

Phosphoretted hydrogen may be employed in some simple experiments. Thus, when bubbles of it are sent up into a jar of oxygen, they burn with much splendour: in chlorine, also, they burn with a beautiful pale blue light.

Why are brimstone matches used in phosphoric fireboxes?

Because the sulphur of the match readily combines with the phosphorus in the bottle, by friction against cork or wood, and inflames: indeed, phosphorus and sulphur combined are more inflammable than phosphorus.

Why is it difficult to light paper by the flame of phosphorus ?

Because the paper becomes covered and protected by the acid formed by the combustion of the phospho

*The best recent paper on the subject (for the controversy is still rife among naturalists) will be found in the Magazine of Natural History, for July, 1830.