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THE

CRITICAL

CRITICAL REVIEW.

For A PRI L, 1786.

Chemical Effays. By R. Watson, D.D. F.R.S. and Regius Profeffor of Divinity in the University of Cambridge. Vol. IV. Small 8vo.

IN

65. Cadell.

N our Fifty-fifth Volume, p. 260, we reviewed, with great regret, the third collection of the bishop's Chemical Effays, as they feemed to contain the laft words of an inftructive and entertaining author, who had brought an abstruse science within the view of the uninformed, and had adorned its facts with an elegant and popular language. But though profeffedly the laft words, the favourite fcience poffeffed too great an influence in his breast: it was the idol of his heart, which he refigned unwillingly, not without a longing lingering look:' it was the parting of two fond lovers, who refolve only to fee each other once more, for one little moment, to speak one short word, and then- -In fact thefe little fits of irre folution feem to have produced the volume before us, and this must be the laft; for the bishop, facrificing to epifcopal decorum,' has burnt his manufcripts, and refigns himself wholly to paftoral cares. Though we regret the public lofs, yet we approve of the motive: like the friends of Virgil, we would, however, have saved the Æneid from the flames; but, from the fame influence, we would have configned it to other hands. The fubftance of this account is taken from the first part of the preface: the rest of it contains fome obfervations on • the utility of an academic inftitution, for inftructing young men of rank and fortune in the elements of agriculture; in the principles of commerce; and in the knowledge of our manufactures. It requires no great eloquence to enforce this hint; for many of thefe branches have extended fo far as to become fciences of an intricate and complex kind; fciences, whofe great corner-ftone is chemistry, whofe bafis is natural hiftory. The defect of authors and practitioners in the knowlege of thefe fundamental branches has confufed the unconnected VOL. LXI. April, 1786. maffes

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masses which we at prefent poffefs, has occafioned fome facts to be obfcure, and others to be misrepresented.

My own notion, indeed, fays Dr. Watfon, of national improvement, fecurity, and happiness, tends not fo much to the extending of our commerce, or the increafing the number of our manufacturers, as to the increafing of an hardy, and, comparatively fpeaking, innocent race of peafants, by making corn to grow on millions of acres of land, where none has ever grown before. Let us but once have as many Britons in the kingdom, as the well cultivated lands of Great Britain are able to fuftain, and we fhall have little to regret in the lofs of America; nothing to apprehend from the partitioning policy of all the continental defpots in Europe.'

If we examine this fubject more intimately, the increafing our internal ftrength by a numerous and hardy population, is not inconfiftent with our external commerce. If the artizan is enervated, he must be fed by the robust ploughman; and the increase of our foreign concerns is, in this way, the moft certain fecurity for that more general cultivation, which shall not outftrip itself, and by feeding us more plentifully with corn, deprive us of animal food. In fpite of fpeculation, cultivation and commerce muft find their proper level, and nothing can disturb it but the rage for colonization, which has been the bane of Great Britain, whofe eyes are yet fcarcely opened by her misfortunes. The plaufible pretext was, that you form a market which will not fail; but the manufacturer now knows, that the beauty of his patterns, the perfection of his manufacture, and the durability of its texture, with a comparative cheapnefs, will open a market every where, among contending, or even favoured rivals; that without these perfections, without the credit which a rich and refpectable commerce can allow, gratitude or treaties are a very infufficient fecurity. Connected with this fubject, Dr. Watfon adds fome obfervations on the mode of education in the univerfities. We need not repeat that it wants reformation, and that this reformation must begin by making diligence and industry respectable in the eyes even of the moft opulent, and of the highest rank. But we have perhaps dwelt too long on fubje&s so different from the contents of this volume.

The firft Effay contains fome mifcellaneous obfervations upon Lapis Calaminaris, Blende, Zinc, and Brafs. The two firft are ores of zinc, and the laft is well known to be compofed of it and copper. Our author defcribes the calamine, difcriminates the different forts, and afcertains the caufe of the lofs of weight, in roafting, to be the efcape of fixed air. The following remarks on analyfis deferve attention, though we ftill think the inference of Bergman to be juft.

• Bergman

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Bergman has ufed the fame method of analyzing other fubftances, containing fixed air, particularly calcareous earths. He found that 100 grains of tranfparent calcareous fpar gave, by folution in an acid, 34 grains of fixed air, and loft by cal-, cination 45 grains; the difference, 11 grains, he fays is water, which, though expelled by the fire, remains mixed with the acid, and hence ioo grains of fuch fpar contain 55 grains of lime, 34 grains of fixed air, and 11 grains of water. I have a little difficulty in admitting this mode of inferring the quantity of water contained in these bodies; I do not abfolutely deny the juftice of it, but I hefitate concerning it; becaufe, from experiments which I made with all the care I could, and which are mentioned in the Effay on calcareous earths, I found that fine tranfparent fpar, very white marble, &c. löft, as nearly as could be estimated, the fame weight, whether they were diffolved in an acid, or calcined in a rong fire.'.

Dr. Watson then proceeds in the Hiftory of Blende, which refembles an ore of lead: it is fo called from its blinding the miners, and leading them into error; and he then relates the hiftory of the reduction of the ore into zinc. Part of this history is detailed in Bergman; but the following is an important addition to it, in the eye of an Englishman.

Bergman, in this hiftory of the difcovery of the method of extracting zinc from calamine, wholly omits the mention of Dr. Ifaac Lawfon; of whom Pott, in his Effay on Zinc, fpeaks very refpectfully, acquainting us that he really obtained fome grains of that femi-metal from calamine. So that though Henckel was the firft, Lawfon was, probably, the second perfon in Europe who procured zinc from calamine; whether he was the Englishman who, according to Bergman, went to China to discover the method of doing it, is what I have not been able to learn with certainty. Our English writers, who have touched on this fubject, fpeak in high terms of Lawfon, I fuppofe from their perfonal knowledge of him, for they do not refer to any written account. Thus Dr. Pryce fays, the late Dr. I. Lawfon obferving that the flowers of lapis calaminaris were the fame as thofe of zinc, and that its effects on copper were also the fame with that femi-metal, never remitted his endeavours till he found the method of feparating pure zinc from that ore." And Dr. Campbell, in his Survey of Britain, is ftill more particular: "the credit, if not the value of calamine is very much raised, fince an ingenious countryman of ours difcovered that it was the true mine of zinc; this countryman was Dr. I. Lawfon, who died before he had made any advantage of his difcovery." The authors of the Supplement to Chambers' Dictionary, published in 1753, expressly afirm, that Dr. Lawfon was the first perfon who thewed that calamine contained zinc; we have now on foot, at home, a work eft blished by the difcoverer of this ore, which will probably make

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it very unneceffary to bring any zinc into England."—To all this I fhall only add one teftimony more, from which it may appear that the English knew how to extract zinc from calamine, before Mr. Van Swab taught the Swedes the method of doing it; though this gentleman, unless I have been mifinformed, inftructed the late Mr. Champion of Bristol, either in the ufe of black jack for the fame purpofe as calamine, or taught him fome improvements in the method of obtaining zinc from its ores. The teftimony occurs in a differtation of Henckel's on zinc, published in 1737, he is there fpeaking of the great hopes which fome perfons had entertained of the poffibility of obtaining zinc from calamine; hopes, he fays, which had been realized in England, Ce qu'un Anglois arrivé depuis peu de Bristol, dit avoir vu réuffir dans fon pays.'

The use of zinc, in making the metals called pinchbeck and brafs, is next defcribed, with the different qualities of thofe metals, either from different proportions of the ingredients, or different countries: an ancient celt was, Dr. Watson thinks, compofed of copper, calamine, and tin. The best brafs is made by combining zinc in vapour, with copper in plates; by this means it is free from all heterogeneous mixtures. Many mifcellaneous circumftances, on the subject, are added, particularly relating to the laws refpecting exportation, and the patents granted for making brafs; but these we can neither extract or abridge.

The Orichalcum of the ancients is the next fubject of enquiry. It is connected with the firft Effay, because it was probably, for the most part, a compound metal, of a nature and appearance fimilar to brass. Dr. Watson has clearly shewn, that it was generally compofed of calamine and copper; but is not equally fuccefsful in proving that arfenic and other fubftances were not fometimes employed inftead of the ore of zinc. A fmall proportion of arfenic, added to copper, or even a larger one, if the mixture be kept longer in fufion, produces a beautiful yellow metal, which admits of a high polish, but turns black by use, especially, if it approaches any phlogistic matter. Dr. Watson thinks, with juftice, that the lapis ærofus of Pliny was not fo called from its corroding quality it was most probably an ore of zinc, which acquired its name from its being usually added to copper (æs) to make the orichalcum; but, on the other hand, we know that the native cadmia is often contaminated by different ingredients; and frequently contains a very small proportion of the calx of zinc, in some instances not one part in twenty-five. If Dr. Watson examines the tenth chapter of the twenty-fourth book of Pliny's Natural Hiftory, he will fee much reafon to fuppofe,

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that the nature of the ancient cadmia is very uncertain and variable.

It was certainly a prevailing opinion among the Romans, that the orichalcum was once a native metal, though the fubfequent imitations of it were chiefly, perhaps wholly, artificial. This is not entirely derived from Plato's account of the Atalantica, in which, however, we perceive many traces of true history, but from the great work of Pliny. He evidently alludes to the original fource of it, when he fays that the earth is now become too effæte and steril to produce it. As the fource was foon exhausted, it probably was an accidental production, from fome internal fires; and, as it was accidental, fo its appearance was various. The different quotations in the Effay before us, evidently prove the variety, which our author's great address has not yet been able successfully to elude. Virgil calls it white, albo orichalcho;' Strabo fpeaks of its being made with a filver-looking metal and copper: Ariftotle, if he really speaks of orichalcum, mentions alfo its whitenefs. Perhaps all these varieties may arife from different proportions of the ingredients, or the different quality of the cadmia they may, however, more probably be owing to the attempt to imitate the original orichalcum in its various ftates. On the whole, its general appearance was probably that of brass, and, like this compound, it was alfo fonorous.

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Tibia non ut nunc orichalco vincta tubæque

Emula.'

This paffage has been variously understood, as either defcribing the clamps and ornaments to be of brass; or, by fome deeper commentators, as a brazen pipe added to the flute. Each interpretation is uncertain; but the passage is chiefly quoted to oppofe the Hybrid etymology; which the bishop has alfo, for different reafons, attempted to confute. It is remarkable, that both Horace and Virgil make the first fyllable fhort, which would not have been the cafe, if it had been derived from the Latin aurum, and the Greek nannóv. Dr. Watfon fuggefts the Hebrew word or or aur, as the etymon of the first part of the word; but Hybrid derivations are very uncommon, and frequently fufpicious. Perhaps ogos, mons, is the true fource; and, though all copper may be called mountain, yet this may have emphatically had this title, if it were mixed by an internal fire, fince it would then have been exclufively found in mountains. While we differ from Dr. Watson in fome particulars, we wish to bear the fulleft teftimony of the learning and ingenuity difplayed in this Effay. The next Effay is on Gun-metal, Statuary-metal, Bellmetal, Pot and Speculum-metal. What we call brafs guns

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