am certain many authors have been mifled by not knowing this? property of metallic falts, viz. that if we diffolve them in a small proportion of water, or if there be fuperfluous acid, the folution will remain perfect when expofed to the air; but if the acid be perfectly faturated with the metal, and the proportion of water to the metallic falt be very great, on expofure to the air it is decompofed, the metal being precipitated in the form of calx, and the acid being loft. This may easily be tried, by taking common green or blue vitriol, diffolving an ounce in three ounces of water by boiling, letting them ftand to cool, and filtering the folution. If this folution be expofed to the air, it will remain perfect; but if we drop a drop or two of it into a wine glass full of water, in a few minutes the tranfparency of the water will begin to be disturbed, and the metal in a fhort time will fall down in a red powder, if it be iron; in a blue powder, if it be copper."

We can only urge, in oppofition to this opinion, that when we have taken up chalybeate water from the fpring, quite pure, with an intention to analyze it, if any circumstance has prevented the immediate experiment, there has been always an ochry sediment, unless it was stopped with uncommon care. This fact cannot be accounted for from dilution, or the escape of a common vitriolic acid : perhaps the water in the experiment mentioned, was not quite pure, the smallest proportion of uncombined lime, or of volatile alkali, no uncommon impregnation in the waters of populous cities, may have had the effect. Even the rain-water in a city fhews marks of impregnation by the more delicate tests.

The vapour from Buxton waters is afterwards examined; and it is highly probable, from the experiments of Dr. Pearson, that a small part of it only is fixed air. There is fome ingenuity in his contrivances to estimate the quantity of fixed air by that of lime water, which it faturates: by this means he finds that Buxton water contains about half the quantity of gas which is generally contained in the water of common springs. If we rightly understand our author, this quantity is enough to fufpend the calcareous earth; but as we have already remarked, he contends for an affinity between it and water, without any other menftruum. The depofition of earth, after boiling, he thinks is not owing to the diffipation of the gas, for that appears equally confpicuous after long boiling as before; but happens merely in confequence of the diminution of the menftruum. On the whole then, our author's analysis is the following; a gallon of water leaves 16 grains of refiduum, containing 10 grains of calcareous earth, 2 grains of vitriolic felenite, 1 grains of fea falt. He found no iron, no phlogistic matter, and no falited magnefia.

The vapour of Buxton water appears commonly in a detached ftate; but these substances alfo admit of a chemical union, for our author finds that it bears nearly the fame affinity to water as common air. It is not the aerial acid, but a phlogisticated air, or, in Dr. Pearson's language, a compound of air and phlogiíton. This is an elaftic fluid, lighter than common air, unfit for refpiration, probably from its inability to unite with any additional quantity of phlogifton. Yet the vapour from phosphorus unites with it; and though by long agitation the phosphorus ceases to fhine, thefe combined airs inflame when expofed to the atmosphere. Fishes die in Buxton waters, seemingly from the heat rather than the contained vapour; but in them, as all other animals, cuftom produces confiderable changes. There are certainly fome instances in which fishes have been found to live in a greater heat.

It has been ufual to attribute the appearance of air in waters entirely to fixed air; but our author corrects this idea, and obferves, that it is only found in the acidulæ. In the Bath waters, and fome others, a portion of this air was before found to be phlogisticated vapour. In the analysis of Dr. Higgins, a Winchester gallon of the water is faid to contain four ounce measures of phlogisticated air, and two ounce meafures of acidulous gas; that is, of phlogisticated air, and

g

of gas. In that of Dr. Pearfon, the gas is about of the bulk of water; and the vapour, which confifts of equal parts of common and phlogisticated air, equals of the whole. On this fubject we are unable to decide. It is probable the quantity of gas itself is variable; or the time in which the water was taken up unfavourable. Our author purfues his enquiry into other properties of this compound; but our limits will not permit us to follow him.

This

Dr. Pearfon next attempts to folve a problem, which we fear is at prefent beyond our powers, that is, the cause of the heat of warm fprings. We fhall not tire our readers with the various hypothefes that have been framed, but only mention that of our author. He thinks, from the quantity of combustible matter in the earth, inflammation may go on for ages, without any confiderable diminution of the fubftance. inflammation may be firit occafioned by the accidental decompofition of pyrites, which it is well known produce heat; and the heat is kept up by the affiftance of the dephlogisticated air, which must be extricated. To account for the uniform temperature, he fuppofes that the heat is fufficient to convert the water into vapour; and we then know that its heat may be greatly increased, if the containing fubftance is able to refift

-N 3

refift its expanfion. In this way, it may flow to a confiderable extent before it is greatly cooled, and may even appear at the furface nearly as hot as boiling water; but if it comes only from a certain diftance, and the inflammation is uniform, it will gradually heat the earth around, and confequently the diminution of the heat will be conftantly the fame. This theory too explains the origin of the vapour, and the great purity of the water; fince, in its progrefs, it actually undergoes a diftillation. We confefs that the many poftulata in this fyftem, in our opinion, are powerful arguments against it; but, in a fubject fo. difficult, it is no difgrace to err. We would only fuggeft to our author, that the vicinity of fprings, of the common temperature to thofe which are warm, are a strong objection to his fyftem; and we know no way of avoiding the difficulty, except we conclude that this tepid diftilled water comes from a great depth. It is certain that springs in general are comparatively fuperficial; fo that, though apparently near, they may really be diftant; but we ought not to make an objection, which muft equally militate against every hypothefis.

The fpontaneous inflammation of black wad is mentioned in the additional notes, as a means by which thefe fubterraneous fires may have been kindled; and this fact, together with the production of dephlogifticated air to fupport the flame, are mentioned by an able chemift with the fame view, Dr. Pearfon failed in the experiment; we shall therefore defcribe the method which fucceeded in our attempts. To half a pound of black wad, well dried and again cooled, were added two ounces of linfeed oil, and they were incorporated · well together the mixture was irregular and clotty, and the whole took fire in about forty minutes. One hundred parts of black wad were found by Mr. Wedgwood to contain 43 parts of manganefe, 43 of iron, 4-5 of lead, and 5 of mica. The remainder was fixed air, by which the manganese is very generally mineralized, and fome water.

Our author does not enlarge on the medical history of this water; he only remarks, that its good effects probably result from the heat, viz. that of 82° of Farenheit, and the phlogiftic vapour. The latter invifcated by a mucilage of gum arab. and drank, produced fickness at the flomach, pain and giddinefs of the head. We fhall felect his method of imitating this water with fuccefs.

We are by this history inftructed how to compofe a water refembling Buxton water in its temperature and impregnation, in the following manner :

Difil a quantity of common hard fpring-water in a gentle heat, in perfectly clean glafs-veffels, fo as to have neither fmell nor tafte; or if it should acquire a fmell by distillation, remove it by expofure to the open air.

To thirty-two ounce measures of this diftilled water in a quart bottle, or in a large Florentine flask, add about fourteen grains of the pureft chalk in fine powder; and four grains of vitriolic felenites, compofed by faturating quick-lime, precipitated from lime-water by gas, with vitriolic acid. Expofe this mixture in a fand-heat of about 140° or 150°, and after it has stood in this fituation a week, or longer, during which time it has been frequently agitated, add about four grains of the pureft sea salt; -then boil this mixture in the flask, or in a veffel of filver, fo as to separate from it all the air it contains, and filter it through paper, previously wafhed, by filtering through it hot diffilled

water.

• Divide this filtered folution into four equal parts, one of which must be contained in a wine-quart bottle; to each of these parts add of a quart, or as much as will fill these quart bottles, of the above diftilled water, previoufly boiled in a Florentine flafk, or in a clean filver veffel, fo as to have expelled all the air diffolved therein, and agitate a short time each of these bottles. Then invert each of thefe bottles in a tub of common hard pump water, and add thereto half an ounce measure of a mixture of one part of common air, and two parts of the compound of air of phlogiston, (formed by expofing air to a mixture of iron-filings and fulphur); then cork the bottles while inverted, and after agitation frequently, and preferving them in an inverted pofition out of the water for three weeks, a month, or fix weeks, upon withdrawing the cork from the bottles inverted in the tub of water, the permanent vapours will be found diffolved or fufpended; for water will rife within the bottles to occupy the place of thefe fubftances.

During the time thefe bottles are inverted and uncorked in the tub of water, as little motion fhould be used as poffible, in order to prevent the mixture of the water of the tub with that of the inverted bottles.

The compound of air and phlogifton ufed upon this occafion fhould be deprived of fmell and tafte, by repeatedly transferring it through water.'

On the whole, though we have not always agreed with Dr. Pearson, we commend his induftry and ingenuity. Several chemical facts, interfperfed in thefe volumes, are highly interesting. We wish that his language was more clear and concife: we wish too, that he had preferred common terms to a more tedious, though fometimes more accurate periphrafis. We diftinguish, in many places, the eagerness of a young man ; but we are forbid to expect the harvest, 'dum feges eft adhuc in herba,'

An Effay on the Waters of Harrowgate and Thorp-Arch in Yorkfire; containing fome Directions for their Ufe in Difeafes. To which are prefixed, Obfervations on Mineral Waters in general, and the Method of analyfing them. By Joshua Walker, M. D. 8vo. 3s. Served. Johnfon.

THIS

HIS Effay is in general an exact account of the nature of thefe celebrated waters; but our author is not acquainted with some of the later improvements in chemistry, or the dif covery of many new precipitants. The following method, for inftance, is vague and uncertain, while the vitriolic acid is. immediately and certainly discovered by means of falited terra ponderofa..

When the vitriolic acid is, in a flate of combination with an alkali, an earth, the inflammable principle, or metallic body, it may be discovered by a folution of lead in the nitrous acid, not quite faturated. The lead will not then be precipitated, either by an alkaline falt, or calcareous earth; becaufe the fuperfluous acid will faturate thefe, and will alfo prevent the precipitation of a metal. This will not, however, hinder the lead from uniting with the vitriolic acid, nor from forming with it a fubftance incapable of folution in water; and which, on that account, always renders the mixture turbid, and causes a precipitation.'

The refult of Dr. Walker's experiments on Harrowgate water, are not very different from thofe of other chemifts. He obferves that it is flightly impregnated with hepar fulphuris, or with an alkali, though this is rather doubtful; common salt, in the proportion of fifteen drachms to a gallon; calcareous earth, twenty-fix grains to a gallon; a fmall quantity of felenite; and fulphureous vapour, in a large proportion. On this fubject we can only obferve, that alkali was fufpected, from its changing fyrup of violets to a greenish colour, after long standing; but this is extremely uncertain, fince common falt will frequently produce the fame effect. Our readers are now fufficiently acquainted with the nature of hepatifated waters, and we think that Dr. Walker has arrived at the conclufion of Bergman, without any affiftance. He has made the discovery without being fully aware of it, and has detected nature in the act of impregnation. He found that, when the vapour had been decompofed by the air, in evaporating the water, that vitriolic acid re-produced the fmell.

‹ I have ventured, says he, in the foregoing pages, to throw out a fuppofition, that it is probable fulphureous waters of the volatile kind, may receive their impregnation from a decompofition of hepar fulphuris, by means of the fuperabundant