common with other gay flowers, is owing to the phlogion in the organs of vegetation, and not to iron, as bas been thought, This phlogillon is manifett by analyfis in the leaves, where the leaft atom of iron has never been difcovered.

There are many lands in Spain which naturally produce faltpetre, fea-falt, and vitriolic falts; but the plants which grow fpontaneously in thofe foils, give by analys the fame product as thofe of their fpecies in gardens, where there never was any appearance of faltpetre, fea-fait, or vitriolic acid.

Analize as often as you pleafe, thofe plants, fo numerous near iron mines, whofe roots penetrate into the very ore, or those that grow in ferruginous and fuperficial earth, I am fure you will not collect from their roots, branches, afhes, extracts, or oils, more iron, than what is found in the fame fpecies of plants that fpring up in places without the leall communication with any fuch minerals.

Whatever efficacy there may be in culture, and manure, to remove, abforb, and open the pores of the earth, enriching the watery parti cles, that rife in the vegetative tubes, conveying new fubftances which contribute to that perfection, we oblerye, from the foil, and which they lofe when tranfplanted, yet they fill attain various fubftances of vegetation from the air, which chemifts may look for in vain in the earth *,

Many plants are emollient in the fpring and fummer, and aftriogent in autumn and winter. Their mucilaginous quality admits of alteration in the tubes, and the combination of earth, air, and water. engenders a vitriolic acid t, just as the alkali and the leaves receive colour from the phlogiston; from whence I conceive the reafon of the pitrous foil in Spain, abounding with fuch a prodigious quantity of fixed natural alkali; which calls to my mind what is fondly advanced by the adepts, "that fome lands have the natural properties of loadflone to attract peculiar fubftances from the air."

It is certain then, that plants have proper tubes to attract the elements, and form a natural fixed alkali, and have peculiar feparate principles which only combine by the means of fire in the act of combuftion to form that artificial fixed alkali I had been taught to believe was the only one that exifted in

nature.

Perhaps the fada and falicornia may thrive better when nurtured by falt water, but it is no lefs certain that the alkaline bafis of common falt is found formed in thefe two plants, and in many others as well as in the barilla, which is fowed in many parts of Spain, where they make as good feap as that famous fort at Alicant made with foda and falicornia, Wich refpect to neutral faits, there are at leaft five fubftances, in which they

are

are found, viz. earth, plants, falt water, mineral, and artificial fub

ftances.

After this digreffion, let us now fee how faltpetre is generally made in France and in Spain; I fay nothing of England or Holland, becaufe they make none, importing what they want from the Eaft Indies, where it is found naturally in the earth, as in Spain, where I have feen faltpetre made with the lixivium of nitrous earth, collected in places where perhaps there never was a tree nor a plant.

In Paris they have feventeen faltpetre works: every thing that is carried on there, as well as in other parts of the kingdom, is done according to royal ordinances, in the manner I am going to relate: the rubbish and filth of old houfes is carried to the works, and pounded with hammers; the duft is then put into cafks, perforated at bottom, the aperture covered with fraw, to give a free paffage to the liquor. Water is then poured on this duft, which in its paffage carries away all the faline matter. This impregnated matter is called a lye, which if they were at that period to boil, would produce faltpetre of a greafy nature; to remedy this, they purchafe the afhes of all the wood fires in Paris, from which they alfo draw a lye that is mixed with the former, then boil up the whole *. In proportion as the water evaporates, the common falt which cryftallizes when hot, foon falls to the bottom of the cauldron, and the faltpetre, which

only cryftallizes when cool, remains diffolved in the water. They draw off this water, loaded with faltpetre, into other veffels, and place it in the fhade, where the nitre cryftallizes. This is called faltpetre of the firft boiling, having fill fome remains of common falt, earth, and greasy matter, incorporated with it; it is conveyed to the arfenal to be properly refined, being boiled over again, and left to cryftallize two or three times, or more if found neceffary; by which means it is cleared of all its impurities, and becomes perfectly adapted to the making of gunpowder, and the other ufes to which it is applied in the arts; but for medical purpofes, it must undergo another purification. Thofe who are

curious of being more exacly informed, may find a very accurate account of thefe works in the memoirs of the academy of fciences by Mr. Petit, to which I refer them.

In Spain, where a third part of all the lands, and the very duft on the roads in the eaftern and fouthern parts of the kingdom, contain natural faltpetre, I have feen them prepare it in the following man

ner:

They plough the ground two or three times in winter, and fpring, near the villages. In Auguft they pile it up in heaps of twenty and thirty feet high: then fill with this earth a range of veffels, of a conic fhape, perforated at bottom, obferving to cover the aperture with mat-weed and a few afhes, two

or three fingers deep, that the water may juft filter through. They then pour on the water, (fometimes without putting any afhes); the lye that refults from this operation is put into a boiler. The common falt, which as we faid before precipitates, and cryftallizes when warm, falls to the bottom of the cauldron in a proportion of 40 lb. to a quintal of materials; then the liquor then the liquor is poured into buckets placed in the shade, where it shoots, and cryitallizes into faltpetre. The great quantity of common falt which accompanies the nitre, makes me think, that the marine acid with its bafis is converted into nitre, The fame earth, deprived of its nitrous quality by this procefs, is again carried back to the fields, and exposed to the elements, by which means in the courfe of a twelvemonth, afited by the allpowerful and invisible hand of nature, it again becomes impregnat ed with a fresh fupply of nitre; and what is still more furprifing, and cannot be obferved without admiring the wonderful works of the omnipotent Creator, the fame lands have produced time immemorial an equal quantity of faltpetre; fo that if the fupreme power was to annihilate all the factitious faltpetre of France and Germany, Spain alone could fupply the reft of the world, without the aid of a fixed alkali, afnes or vegetables, if public economy joined hands with induftry, and affited in bringing thefe great points to perfection. I once asked one of thefe people the reafon of

that conftant production of faltpetre, but his only answer was, "I have two fields; I fow one with "corn, and have a crop; I plough "the other, and it furnishes mo "faltpetre."

This faltpetre thus cryftallized is fimilar to that of Paris of the first boiling. In Spain they only boil it once more, and it becomes perfect, and proper for making of gunpowder, aqua fortis, and other purposes of the shops. Its bafis placed in a cellar, attracts the dampnefs of the air, lofes its activity, and forms a fixed alkali, which mixed with the vitriolic acid, forms a vitriolated tartar, a certain proof that the nitrous air of Spain is natural and perfect in itself, without the affiftance of any fixed alkali whatever.

I shall not dwell upon the proportion of faltpetre, fulphur, and coal, ufed in the making of gunpowder; as it depends upon experience, and is generally known. I was prefent at the proofs made by the king's officers in Granada, to ascertain whether the powder" had the qualities required, in order to be admitted or refused; but I do not think thofe proofs were to the purpose, as new made powder perhaps may throw a ball to the diftance required; yet to form a true judgment of its real quality and goodness, it should be tried in different places and climates, and at various feafons of the year; for I am convinced that the gunpowder which would come up to the ftrength required by the king in the dry and warm climate of Andalufia, would be found defi

cient in the damp and moist air of Galicia, which fhews how little fuch experiments are to be depended upon. Of all the inventions I know of for this purpose, the least imperfect is that of Mr. Darcy, a defign of which may be feen in the firft volume of Mr. Beaume's treatife on chemistry.

When the Count de Aranda was director of the engineers, I remember an old officer of artillery informed me that in the laft wars in Italy, he had feen barrels of gunpowder, that were good in the morning, and bad the next night: this did not furprize me, knowing the variations of weather, and the effects of dampnefs piercing thro' the cafks and damaging the powder, fo as to render it unfit for fervice, for which reafon every precaution fhould be taken to guard against these inconveniences.

Extract from Dr. Ingenhoufz's Account of a new inflammable Air, which can be made in a Moment, without Apparatus, and is as fit for Explosion as any other inflammable Gaffes.

[From the Philof. Tranf. Vol. 69.]

THE discovery of the various

or gaffes becoming powerfully explofive, when they are mixed with a fufficient quantity of common air, and fill more fo when they are combined with dephlogifticated air, is one of thofe improvements in natural philofophy which, giving occafion to various amusing and interefting experiments, have caft at the fame time a new light upon fome powerful agents, whofe mif

chievous force was known, though their nature was fill in the dark.

As thofe inflammable airs have been of late years one of the principal philofophical amufements, I intend to lay before the Royal Society an eafy method of producing, without any trouble or particular apparatus, fuch quantity of an inflammable air or gafs as may be required.

Being at Amfterdam in November 1777, Meffieurs Eneae and Cuthbertion, two ingenious philofophers of that city, were fo good as to fhew me fome curious experiments with explofive and inflammable airs of different kinds. They produced an inflammable air, by mixing together equal quantities of oil of vitriol and fpirit of wine, and applying heat to the phial containing the compound. A great quantity of white. vapour was extricated, which, paffing up the inverted receiver filled with water, fettled at the top and depreffed the water, as other airs do. This air foon became clear, the white fumes being abforbed by the water. This air was eafily lighted in an open cylindrical glafs, and burnt almo as clear as a candle, the flame defcending gradually lower and lower till it reached the bottom. A very

little quantity of this air mixed

air, for inftance, one fourteenth or one tenth part, and kindled by an electrical park, exploded with a very loud report, and shattered the glafs to pieces. in which it was kindled, when it did not find a ready vent.

They had contrived a kind of a piftol for the purpofe, confifting of a ftrong cylindrical glass tube with a pillon adapted to it. To the

end

:

end of this tube was fixed a brafs barrel, like that of a common piftol into this barrel a brass bullet was put loose, so that the barrel was placed a little above the level, to prevent the bullet rolling out. The barrel was directed to a board of oak at eight or ten feet' distance. A proper quantity of common and inflammable air (produced in the manner above mentioned) being drawn into the glafs tube by means of the pifton, it was fired by directing an electrical explosion through it. The explofion was very loud: the ball hit the board with fuch a force that it made a ftrong impreffion in it, and recoiled with a confiderable force, fo as to hit the wall behind us, and to put us in fome danger of being hurt by its rebounding force.

The fame gentleman told me, that this inflammable air had in fome refpects the advantage over the inflammable airs extracted from metals by the vitriolic or marine acid, and that extracted from mud or marfhes; because this air being heavier than either of these airs, and even than common air, is not fo easily lost out of an open veffel; and, that when it efcapes into the open air, it agreeably perfumes the room with the fmell of fpiritus vitrioli dulcis or æther; whereas the other inflammable airs, which from their lefs fpecific gravity efcape easily into the common air, yield an offenfive, difagreeable itench.

Mr. Eneae, having examined the Ipecific gravities of the different inflammable airs compared with common air, favoured me with the following refalt of his inquiries:

A vellel, which contained the

weight of 138 grains of common air, contained 25 grains of inflammable air extracted from iron by vitriolic acid, and 92 grains of inflammable air extracted from mud or marfhes, and 150 grains of that extracted from oil of vitriol and spirit of wine.

I was much pleased with the above-mentioned experiment, and immediately thought that the operation of extracting this inflammable air or vapour could be difpenfed with by employing vitriolic aether, which in reality is contained in the vapour expelled by heat from oil of vitriol and fpirit of wine, which vapour, condensed in the process of diftillation, yields æther.

The first attempts I made proved unfuccefsful; however, the fons why I did not fucceed in the beginning I found afterwards to be, either that I employed too great quantity of æther, or that the air or vapour of the æther was not thoroughly incorporated with the other air; for the fame number of drops of æther poured into the air pistol, which would not produce an explofion when the piftol was not fhaken, made a very loud one when it was forcibly agitated.

The fureft method of fucceeding I find to be the following: I dip a fmall glafs tube, open on both fides, and the bore of which is one twelfth of an inch in diameter, into a phial containing æther, and when two or three drops of the liquid have entered the tube I apply my finger to the upper end of it, to keep the liquor fufpended. I take the tube out of the phial, and thrust it immediately into a fmall caoutcbouck, or elaftic gum bottle: this