of which latter sort are oils, sulphurs, and such bodies as are of a combustible nature, by abounding with phlogiston, the matter of inflammability. From these bodies fire may be raised many different ways.

Iron filings, and powdered sulphur, mixed together in equal quantities to the weight of fifty pounds, and made up into a paste with water, will in a few hours acquire a very great heat, and if the mixture is confined in a close vessel, it will take fire and explode. The experiment is sometimes made by confining these ingredients under ground, and ramming the earth hard over them, to illustrate the doctrine of volcanos and earthquakes, which may reasonably be supposed to arise from subterraneous magazines of sulphur and the ore of iron, raised to a fermentation by the accession of water, and acquiring an immense force from the compression of their heated vapour under an incumbent weight of earth, especially when the materials are lodged deep in the bowels of the earth. This is confirmed by the kind of matter which is cast out of volcanos; their lava, or melted mineral matter, seeming to be chiefly composed of iron and sulphur.

The industry of the chemists led them to

the

the discovery of an extraordinary substance, made of the putrid juices of animals, deprived of their volatile parts, and urged with the most vehement heat of a reverberatory furnace. The matter which then comes over is unctuous and solid like wax, and so strongly impregnated with the matter of fire, that it will burn away in the air with a penetrating urinous smell; but if it is secured from the air, by being laid under water, its fire will there keep cold for many years, and be as vigorous on occasion as it was at first. I know not what to call this but a kind of unctuous lime, or sulphur, rendered more. open and active by a smoking spirit of salt. The oil and sulphur of this strange substance will not permit the water to have any effect upon it, but that of protecting it from the air. I have preserved a small piece of this phosphorus in a phial of water for above twenty years; it was not more than an inch long at first, nor thicker than the small end of a tobacco-pipe; yet it has furnished me with matter for many experiments, and there is enough of it still left for many more. The words which are written with it upon paper will shine in the dark like the light of a glowworm, and last for half an hour; when they

begin to fail, a blast of air will excite them afresh, and if they are presented near to a fire, they become exceedingly vivid, and will scorch the paper. If a small particle is laid upon coarse paper, and rubbed swiftly over with the flat side of the blade of a knife, it will instantly set fire to the paper, and break out into a bright flame; than which there is no experiment better adapted to shew the effect of attrition upon the matter of fire *.

There

* More particulars concerning this body may be learned from the chemical writers. The following account is extracted from Macquer, one of the most sensible and ingenious modern writers on chemistry. "From the marine "acid combined with the phlogiston results a kind of sul"phur, differing from the common sort in many respects, "but particularly in this property, that it takes fire of it"self, upon being exposed to the open air. This combina"tion is called English phosphorus, or phosphorus of urine, "because it is generally prepared from urine. This combi"nation of the marine acid, with the phlogiston, is not ea"sily effected, because it requires a difficult operation in

peculiar vessels. For these reasons it does not always "succeed; and phosphorus is so scarce and dear, that hi

therto chemists have not been able to make on it the ex"periments necessary to discover all its properties.-Phosphorus resembles sulphur in several of its properties; it is soluble in oils; it melts with a gentle heat; it is very combustible; it burns without producing scot, and its

"flame

There is another kind of phosphorus prepared from a mixture of powdered alum and wheat flour, which are ustulated in an open vessel, but not quite reduced to a calx, then put into phials close stopt and coated with clay, and kept for some time in an intense heat, but not so long as to burn away the sulphur. If the phials are opened when quite cold, the matter will instantly take fire with the air, and burn away with a sulphureous smell.

It is also possible to excite fire by the mix

ture

" flame is vivid and blueish." vol. I. chap. iv. § 3. The same author has extracted from Mr. Hellot, a Member of the Academy of Sciences at Paris, the whole process for making the phosphorus of urine, in which there are many curious and wonderful circumstances; but the account is too large to be given in this place. The first person that hit upon phosphorus was Brandt, a citizen of Hamburgh, who worked upon urine with the hope of finding the philosopher's stone. The operation (when the material was known) was also discovered by Kunkel, and our Mr. Boyle. M. Margraaf of the Academy of Sciences at Berlin, discovered a way of contracting the operation, so as to produce the phosphorus in four hours. After many critical observations on the substance, he imputes its property in a great measure to a subtile vitrifiable earth combined with the other principles. See Macquer's Elements of Chemistry, part I. chap. iii, process 2,

ture of two cold fluids; the one a lean, hungry, penetrating acid, distilled from oil of vitriol (as it is commonly called) and saltpetre, the other a rich and ponderous vegetable oil abounding with sulphur; so that the mixture of these two forms a kind of fluid gunpowder. The ingredients of gunpowder being solid and sluggish of themselves, must be put into action by the contact of fire already excited; but these fluid ingredients are driven so forcibly into each other, that the bare mixture produces a collision sufficient to kindle an actual flame, which the materials support till they are burned away, and nothing is left behind but a black crust or cinder. The two fluids most proper for this experiment are oil of sassafras, or oil of cloves, and the strong spirit of nitre above mentioned. Sir Isaac Newton describes the extraordinary effect of these two fluids when mixed together in a small quantity in vacuo. "When a drachm of the "above-mentioned compound spirit of nitre was poured upon half a drachm of oil of caraway seeds in vacuo, the mixture imme

66

diately made a flash like gunpowder, and "burst the exhausted receiver, which was

a