even nitre itself by this means is made to contain more phlogifton than liver of fulphur or charcoal. So far Dr. Hopfon and the antiphlogiftians are found to differ in theory. But the doctor endeavours to account for the matter..of fire itself, and pofitively afferts that it is compofed of heat and light. Thus far he outstrips the antiphlogistians in philofophy, for they have not as yet endeavoured or prefumed to account for the conftituent principles of fire. However this idea of fire has been entertained by many long before Dr. Hopfon, and even now by perfons who never heard of his Efay on Fire. But we can see very little merit to be claimed either by the doctor or any other man for this fuppofed difcovery, which is fo truly hypothetical and chimerical. It is very much to be lamented that fo excellent a science as chemistry should be fo much embarraffed and obfcured by fo many whimsical and fanciful theories. The truth of every doctrine is to be ascertained by the univerfality of its application, and the general connexion and agreement of all its parts That doctrine must be erroneous that leaves out a fingle link, or fails in explaining even one phenomenon, as the great Newton has long fince obferved.

Zimolichny, or the chemistry of fermenting bodies, is the subject of the fifth chapter. This certainly merits the reader's attention. As a fpecimen, we have felected the following quotation.

The restoration of pricked, and the melioration of four wines, is effected in the fame manner as a poor and watery wine is changed into a good fpirituous and ftrong-bodied liquor. The cause of thefe defects lies in the proportion of the natural conftituent parts of the whole mixed; in confequence of which, the aqueous and acid part predominating either naturally or through neglect, the wines are deficient in genuine fpirit. To remedy thefe defects of the inferior forts of wines, and to raife the liquor to the ftandard of the more generous wines, either the part which is deficient must be restored by art, or that which is redundant abstracted. With a view to the former object, they must be charged with a larger portion of a homogeneous faccharino mucilaginous fubftance, in which a confiderable quantity of vinous fpirit is contained in a latent ftate; and with which it must be made to ferment afresh; in confequence of which a different proportion of their conftituent parts is produced. This end is attained in the following manner: First, ten pounds of lump fugar, broken into fmall pieces, and fifteen of fresh Spanish raifins, without either stalks or ftones, are put into a clean and fweet cafk; upon which the cafk is filled about three quarters full with wine, and the bung is put in very flightly.. During the firit five days the cafk is fhaken twice a day, and, in order to promote the fermentation of the liquor, fixty drops of fpirit of vitriol, and one hundred drops of a folution of falt of tartar in water, are added to it, each feparately, care being taken, however, after the addition of the former ingre

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dients, to shake the cask well before the latter is poured in. If, after ten or twelve days are elapfed, the wine does not begin to ferment, the fourth part of each of these ingredients may again be added, and the liquor let alone for three or four days longer. If the fermentation does not then enfue, the fourth part of the fame ingredients may be added once more. The cask, in the winter time, should be kept in a tolerably warm room, but in the fummer in some convenient warm place in the open air. The whole fermentation ought to laft forty days in all; but if it fhould ceafe fooner, it may be excited again, by dropping into it alternately a small quantity of the liquors before mentioned. When, during the fermentation, the wine grows bitter, it is a good fign.'

Phlogurgy, or the chemistry of inflammable bodies, is treated of in the fixth chapter. The method of obtaining the different ethers is here explained, and the effects of the different inflammable bodies on each other, together with a table exhibiting the quantity of ethereal oil obtained from different vegetables.

The outlines or general principles of painting, dying, varnishing, &c. are pointed out in the feventh chapter. A novice in chemistry may poffibly acquire fome knowledge by the perufal of this; but the philofophical artist will find nothing in it particularly new or interefting.

Á defcription of economical chemistry is given in the fecond book. Confidering that the application of chemistry to agriculture is but yet in its infancy, the prefent undertaking muft appear both fcientifical and judicious. We shall give the following extract, for which we are indebted to the editor:

The proper food of plants,' fays he, appears, from every confideration, to be the vegetable, or organic principle. This they get either from other plants, in which this principle is developed by the procefs of putrefaction, or from animal fubftances under fimilar circumftances, or lastly, from the aerial acid, of which this fubftance conftitutes the bafis, and which, on account of its poffeffing a greater fpecific gravity than common air, is always near the furface of the earth, and confequently in readinefs to be abforbed by the plants. Hence we fee that the alpine plants, viz fuch as grow upon high hills and mountains, are of a much fmaller fize than the vegetables that grow in an equally poor foil in the valleys; the atmosphere, in that elevated fituation, containing a very inconfiderable portion of aerial acid. Ex nihilo nihil fit, is an axiom of incontrovertible authority, not only in phyfics, but every other department of science. If it be not from the fource abovementioned, whence comes the growth of vegetables in distilled water? and particularly the vaft increase of the vegetable principle, whether in the form of fugar, farina, oil, or mucilage? In the bulbous plants, indeed, this principle appears to be chiefly furnished by the bulb or hybernaculum, which is always of a farinaceous nature. In mint too, concerning the growth of which

in diftilled water fo much has been faid, the addition made to its bulk may, in a great measure, be accounted for by the decompofition of water; as this plant contains a large portion of etherial oil, that is, of hydrophloge and phlogifton; but a very inconfiderable quantity of farina, fugar, fixed oil, or mucilage; and if this plant should be found to receive a very trifling acceffion of fubftance (and particularly of fuch matter as contain the vegetable principle), when tranfported to very high and barren mountains, to which the aerial acid has very little accefs, and kept in a proper degree of warmth, the portion laid down here would be further confirmed by experiment; an experiment as easy to be made (by persons properly fituated for it) as it would be decifive and extenfive in its confequences. But to return to the charge: whence then proceeds, in moft plants, this vast acceffion of vegetable matter? Not from the air, I mean the pure air of the atmosphere; nor from the mephitis, which is constantly mixed with it in the atmosphere; for these are fimple fubftances; and in every change they undergo, and from every combination they have entered into, may always be recovered in their original form. Neither can this matter proceed from the fixation of light in the plant, for that conftantly produces phlogifton; nor, finally, from the decompo fition of water, for this produces hydrophloge, which, combined with light or phlogiston, generates inflammable gas, and (with the addidition of the vegetable principle in different proportions) oils, raifins, and the green colouring matter exhibited by the leaves, and fometimes the ftalks and other parts of almost all vegetables that have been expofed to the light during vegetation. Both in the decompofition of water, and in that of fixed air by plants, the pure air is feparated by the excretory veffels at the upper furface of the leaves, and makes it escape into the atmosphere.'

The third and laft book of this volume, denominated philofophical chemistry, comprehends, under different heads or chapters, ift. The definition of philofophical chemistry and physical elements; 2dly. Phosphori; 3dly. Pyrophori; 4thly. Water; 5thly. The analysis of mineral waters.

The last of these chapters, relative to the analyfis of mineral waters, we by no means think entitled to our praife. We are willing to allow this publication every merit which it deferyes; but, as a fyftem of Chemistry, we deem it unequal to the title which it affumes.

ART. XIV. Philofophical Tranfactions of the Royal Society of London, Vol. LXXVI. For the Year 1786. Part I. 8s. 6d. fewed. Davis. London, 1786.

4to.

THIS volume commences with Obfervations on the Graduation of Aftronomical Inftruments; with an Explanation of the Method invented by the late Mr. Henry Hindley of York, Clock-Maker, to divide Circles into any given Number of Parts. By Mr. John Smeaton, F. R.S. Communicated by Henry Cavendish, Efq. F. R. S. and S. A. The method of dividing circles, for the purpose of astronomy and navigation, is a fubject that has much exercifed the ingenuity of mathematical artifts, and been varioufly determined by men of distinguished abilities in science. Mr. Smeaton gives an historical account of the different modes which have been recommended, and makes judicious obfervations on each of them. He had been of opinion that the art of graduating inftruments was brought to fuch a degree of perfection as it was hardly poffible to surpass; until having feen a piece of mechanism, conftructed by Mr. Hindley at York, he was led to think that the problem was ftill capable of farther improvement. With the view of accomplishing this purpose, he applied himself diligently to the subject; and he describes with great precifion the fteps by which he proceeded in executing the various parts of the graduating inftrument. For the detail of thofe particulars we must neceffarily refer our readers to the paper itfelf; obferving only that he has fuggested many ingenious obfervations relative to the point in question, and fuch as will be justly regarded as ufeful, both in conftructing and practifing with thofe inftruments, the excellence of which "depends on the accurate divifion of circles.

Art. II. A Series of Obfervations on, and a Discovery of, the Period of the Variation of the Light of the Star marked & by Bayer, near the Head of Cepheus. In a Letter from John Goodricke, Efq. to Nevil Maskelyne, D.D. F.R.S. and Aftronommer-Royal. The obfervations in this paper are numerous, and appear to be accurate: but they are of fuch a nature as will not admit of an abridged account.

Art. III. Magnetical Experiments and Obfervations. By Mr. Tiberius Cavallo, F. R.S. Mr. Cavallo's object in this paper is to fhew the properties of fome metallic fubítances with refpect to magnetism; and the experiments which he recites feem to afcertain fome remarkable facts. They relate chiefly to the properties of brafs, and tend to prove that this compound metal, which is often magnetic, does not owe its magnetism to iron, but to fome particular configuration of its component particles,

particles, occafioned by the ufual method of hardening it, which is by hammering.

Art. IV. On Infinite Series. By Edward Waring, M. D. F.R.S. Lucarian Profeffor of Mathematics in Cambridge. This paper confifts of algebraical calculations which admit of no particular detail.

Art. V. Experiments on Hepatic Air. By Richard Kirwan, Esq. F. R.S. Our chemical readers need not be informed that hepatic air is that fpecies of permanently elastic fluid which is obtained from combinations of fulphur with various fubftances, as alkalies, earths, metals, &c. This air poffeffes many peculiar properties, and is found to act an important part in the economy of nature. The experiments related by Mr. Kirwan were all made over quickfilver, and feveral times repeated. It appears from them, in the firft place, that the blue fmoke emitted by the faline liver of fulphur, when the latter is heated, confifts chiefly of fixed air, and the white or yellow finoke of fublimed; and that no hepatic air thus formed, nor vitriolic air, unless the retort be fo large as to contain a fufficiency of common air to admit the combuftion of part of the fulphur. It appears, in the second place, that the aerial or any other acid, combined with the alkali, muft be expelled before the alkali will combine with the fulphur.

Magnina, free from fixed air, heated in the fame manner with fulphur, afforded no hepatic air when an acid was poured on it.

Mr. Kirwan also procured this air from a mixture of three parts of filings of iron, and one of fulphur, melted together, and treated with marine acid. It is remarkable that this fulphurated iron, diffolved in marine acid, affords fearce any inflammable, but moftly hepatic air. Various other refults, contributing to illuftrate the fubject, are deduced from thefe experiments, for which we muft refer to the work.

Art. VI. Obfervations on the Affinities of Subftances in Spirit of Wine. By John Elliot, M, D. The purpose of this inquiry is to evince that certain decompofitions will take place in fpirit of wine, which will not in water, or in the dry way. In water alkalies will not feparate lime from expreffed oils; but in fpirit of wine an alkaline foap will be formed, and the calcareous earth will become mild. Sea falt, added to diachylum, produced in fpirits of wine, an alkaline foap, and a muriated lead. This, however, the author juftly obferves, is a philofophical experiment, and probably cannot be rendered useful on many accounts.

Art. VII. An Account of fome minute British Shells, either not duly obferved, or totally unnoticed by Authors. By the

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