but with difficulty, and by extraordinary means, unite more intimately, and are with greater difficulty decompofed. Mercury, for instance, unites more readily with the nitrous than the marine acid, neverthelefs it adheres more obftinately to the latter.

Hence we may conclude, that we are not abfolutely to determine, that one body has no affinity with the other, becaufe we are not acquainted with any means of uniting them. On the contrary, it feems certain that all bodies in nature have with each other a certain degree of affinity, a facility of uniting, a certain degree of cohefion when united, and confequently that there are no combinations which are abfolutely impoffible; but that this degree of affinity differs, according to the different states in which bodies are found.

But fince the defect of union between two bodies really prevents their affinity from being manifeft, till chemistry is fo far advanced as to produce combinations which feem at prefent impoffible, we may continue to regard thofe bodies which refufe to unite as having no affinity with each other. Thus, for example, we fay that oil has no affinity with water, lead with iron, iron with mercury, because in fact, thofe bodies do not unite directly; fo that the affinity which they may have with each other is ineffectual with regard to us. On the other hand, as the affinities of bodies which unite produce in the operations of chemistry effects proportioned to the facility of uniting, and the force of their adhefion, we may confider the affinities of bodies in general, as being in a compound ratio of these two properties, &c.

Compound affinity is that in which there are more than two bodies acting upon each other. We are firft to confider that in which only three principles are concerned. Two of thefe being united, if a third is prefented there will appear phenomena of compofition or decompofition differing according to the affinities which the three bodies have to each other.

1. Sometimes the third principle, uniting with the other two, forms a compound of three principles. For instance, if to amafs compofed of gold and filver a portion of copper be 1-added, this third metal unites with the other two, and there refults a compound of three principles: this happens when the third principle has an equal, or nearly equal, affinity with the two others as they have with each other.

2. The fame thing may alfo happen, though the third principle has no affinity with one of the two already united. But then it is necefiary that the third principle fhould have the fame affinity with one of the two, as they have with each other. In this cafe, that of the two principles which acts as the bond of union between thofe which have no affinity, is called intermediate. This therefore may be called intermediate affinity. If,

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for

for example, we put into water the compound called hepar ful phuris, the two principles of which are fulphur and fixed alkali, it will, without being decompofed, unite with the water and thus form a new compound of three principles. Now, water and fulphur alone are incapable of uniting; but the fixed alkali having a confiderable affinity as well with water as with fulphur, it acts in this cafe as an intermediate principle. Let us oblerve, that in this intermediate affinity, that of the intervening principle is weaker by being thus divided than it would have been with either of the two feparate.

3. Sometimes a third principle applied to a compound of two others, unites with one and obliges the other to quit entirely that to which it was firft united. In this cafe there is a total decompofition of the fift compound, and a new combination takes place. This happens when the advening principle has a greater affinity with one of the others than fubfifts between themselves. For instance, if we mix an alkali with the folution of a metal in an acid, the alkali, having a much greater affinity with the acid than with the metal, feizes the acid and obliges it to quit the metal, which falls to the bottom, the latter having lefs affinity with the acid than the acid has with the alkali.

4. It happens in fome inftances, that the fame principle which through the affinity above mentioned, had been feparated from another, alfo caufes in its turn the feparation of the fame principle by which it had before been precipitated. This reciprocal affinity takes place when the two principles which have alternately feparated each other, happen to poffefs an almoft equal degree of affinity to the third principle, and that their feparation is occafioned by fome particular circumftance relative to fome of their properties.'

Our chemical Readers will perceive from what we have. tranflated from this article, that the author, whoever he may be, is not ignorant of his fubject. We cannot, however, help obferving, that in this article, as in many others, he is unneceffarily prolix, and tautological in his manner of expreffion. The book is nevertheless by no means an useless performance.

B...t

Hiftoire des Revolutions de l' Empire Romain, &c. That is, The History of the Revolutions of the Roman Empire. By S. N. H. Linguct. 12mo. 2 vols. Paris, 1766.

THIS work is a continuation of Vertot's hiftory of the revolutions of the Roman republic, and though inferior to the masterly performance of the ingenious Abbè, has notwithftanding a very confiderable degree of merit, There is a fpirit

and

2nd rapidity in the Author's ftyle well fuited to his fubject; his 513 obfervations are often new, and generally juft; he appears to have read with taste and judgment the works of those celebrated ancients, who have written concerning the Roman emperors, and to have been upon his guard against that blind and often malevolent credulity which is too obfervable in almost all of them.

Thofe hiftorians who wrote after the reign of Tiberius, Nero, Caligula, &c. are as extravagant in their fatire, M. Linguet imagines, as their predeceffors were in their flattery of thofe men, whom a fatal grandeur exposed both to the one and the other. Even Tacitus himfelf, he thinks, is not to be excepted. His hiftory, he acknowledges, is the moft perfect production of the kind, that is left us by antiquity; full of fublime ftrokes, which fhew a profound genius, formed for giving leffons to pofterity; but formed likewife perhaps for impofing upon it, He indulges too much in a certain fharpnefs and feverity which was natural to him, and which, indeed, is in fome measure pardonable in thofe, who, having lived long in the world, perfuade themselves at laft that there is nothing to be feen in it but counterfeit virtues, or disguised vices.

This difpofition, our Author fuppofes to have been as much the effect of natural temper in Tacitus, as of reflection. His make and conftitution led him more to fatire than panegyric; and the influence of conflitution upon the manner of feeing and painting objects is well known. Who knows, befides, fays our hiftorian, whether Tacitus, in following his natural inclination, did not mean to pay his court to thofe princes whom he commends, and under whofe reign he wrote? The most extravagant satirifts are often the most artful and delicate flatterers. Who can affirm, that the implacable cenfor of Tiberius was not defirous of making what he faid of the fucceffors of Auguftus contribute to his advancement under the fucceffors of Domitian?

Whether Tacitus was influenced by fuch motives, or not, our hiftorian thinks he may be fuípected of it without any injuftice, It is impoffible, we are told, to believe all that he fays in regard to the firft Cæfars. He draws fuch a horrid picture of their debaucheries, and of their refinements in cruelty, as is more difhonourable, in fome measure, to human nature itself, accoing to M. Linguet, than to those to whom they are imputed.-How far thefe reflections upon Tacitus are juft, thofe who are acquainted with his character and writings muft determine for themfelves; that there is fome truth in them, the most fanguine of his admirers, we apprehend, will readily allow.

Our hiftorian is no advocate for Tiberius, and it would be ftrange indeed if he were; from a perfuafion, however, that his

vices

vices have been exaggerated by Tacitus and Suetonius, he feems defirous of fhewing that he was lefs cruel than the malignant eloquence (as he expreffes himself) of the former of thefe historians, and the weak credulity of the latter have represented him. In regard to those beaftly exceffes he is faid to have been guilty of, after the death of Sejanus, when he was near feventy years of age, M. Linguet fuppofes it highly improbable that libertinifm fhould fpring up in his heart, at a time when almoft every other paffion was extinguifhed, and thinks it quite incredible that the froft of old age thould kindle fuch irregular tranfports as are seldom found in the boiling heat of youth. As he has nothing to oppose to the teftimony of Tacitus, however, but the feeming improbability of the thing; though what he advances on this head is very ingenious, and feems to proceed from a love of truth and a generous concern for the honour of human nature, yet it has certainly no great weight in it, efpecially when we confider what filthy monsters there have been, and still are in the human fpecies, and that Tiberius, even allowing the truth of all that M. Linguet has faid, is still a deteftable wretch, and feems capable of all that Tacitus lays to his charge.

Our Author's hiftory reaches from Auguftus to the death of Alexander Severus; an interefting period, and full of important inftruction. It prefents us with a view of the greatest republic on earth, changed by an ufurper into an immenfe monarchy. This monarchy foon degenerates into a cruel tyranny. The Romans, after having been fo long the moft haughty nation of the univerfe, become the meaneft of flaves. At certain times, indeed, they recover fome degree of their former vigour, but they always employ it to tear their own bowels. Thofe once haughty conquerors, thofe intrepid defenders of their liberties, now no longer diftinguifh themfelves but in civil wars, and have no other object of their ambition, but the choice of a tyrant.

Such are the objects our hiftorian prefents to his readers, and he prefents them in a lively and agreeable manner. His work, indeed, confidered as a continuation of Vertot's hiftory of the revolutions of the republic, is juftiy, though modeftly characterifed by himself;-it is, fays he, like a flatue with its head by Phidias, and the rest of its body by one of his difciples. R.

De Arte Medendi apud Prifcos, Mufices ope atque Carminum, Epiftola ad Antonium Relhan, M. D.

An Epifle to Anthony Relhan, M. D, on the Art of Healing by Mufic and Poetry among the Ancients. London. Svo. Is. Johnfton.

HE intention of this epiftle, which appears to have been Twritten in Holland, is to prove, chiefly from the autho

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Tity of the ancients, the great ufe of mufic in the cure of diseases. Mufic is used by the author as a general term: Mufice, fays he, vox generalis eft, ficut et Plutarcho videtur, qui libro fuo totam hunc artem complectenti, meqi peons infcripfit. Ejus partes funt vox, inftrumenta et carmen, five vocabula metri cujufdam legibus adftricta. Apud prifcos enim nullum fuit carmen nifi cum mufice conjunctum. He begins with the Greek phyficians, then confults their hiftorians, and afterwards quotes from their poets fuch paffages as ferve to prove his pofition. From the Geeks he comes to the Romans, among whom Cicero, Pliny, Virgil, Horace, Propertius, Tibullus, are his advocates. Having proceeded thus far, quæ plurima reftant, fays he, in banc rem teftimonia, fciens prætermitto, ne jactationi potius quam neceffitati, id tribuiffe videar. Nam ex iis quæ attuli, fatis patent, quas volo, conclufiones. He then calls fcripture to witness, particularly in the inftance of David's curing Saul by means of his harp. Having now done with facts, he proceeds to fupport his thefts from nature and philofophy. Confidering man, according to Plato, as compofed of four diftinct parts, viz. an earthy, a vegetable, an animal, and a spiritual, he fhews how thefe are feparately affected by mufic. Speaking of the first, Si vitreos calices, fays he, difrumpant moduli difcordes quamvis leniffimi, quid nervis corporum tenuiffimis, et delicatiffimis, fæminarum præcipue, exiftimandum eft? Tale quid et ipfi nervofi, ut vocitas, fentire videntur; quorum nonnulli, ingruente jam morbo, femet in vafa vitrea mutatos effe arbitrati funt.

With regard to the fecond principle of human nature, he thinks it hard that we should deny to vegetables that fenfibility which hath been granted to earth and tones.Senfum negas eum, quem faxis ineffe fateris? Non adeo abfurde philofopharis. Eruditos vero, præcipue focietatis veftræ Regiæ focios, iterum iterumque voco in partes, ut hanc rem tandem faceffant, nec vegetabilia finant, pulcherrimum naturæ opus, a finibus mufices diutius exulari, ubi faxis, lutoque conceditur locus.

As to the third principle, namely, our animal part, its fenfibility to mufic is too univerfal to require any proof; neverthelefs, he thinks it not amifs to hear what the poets fay upon this fubject. We tranfcribe the following paragraph partly out of regard to our own Shakespeare, and partly to fhew what great things were expected, by ftrangers, from Dr. Johnfon's edition of that poet. tamen paulifper audiamus, quorum carmina in hoc loco melle dulciffimo Quid in re tam apertâ verbis opus eft? Poctas dulciora fluunt. Equibus præcipue laudandus mihi Shakespeare veftras, tum jure fuo, tum quod ei plurimum debeo. Hujus enim accenfus amore, lingua Anglicana primum operam dedi, donec eam et legere, et intelligere potui, quamvis nec loqui nec fcribere poffum; et nunc eum dies noctefque libentiffime legere foleo. Eundem audio bonis

avibus