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his fubject, and then he intimates that the whole is a lying fable, and he intimates it in fuch a manner, that it seems scarcely poffible to clear him from this imputation.' The ivory gate puzzles every commentator, and grieves every lover of Virgil. Yet, fays our author, it affords no advantages to the bishop of Gloucefter. The objection preffes as hard on the notion of an initiation, as on that of a real descent to the shades. The troublesome conclufion ftill remains as it was; and from the manner in which the hero is difmiffed after the ceremonies, we learn that in those initiations, the machinery, and the whole fhew was, in the poet's opinion, a reprefentation of things which had no truth or reality.'

Dr. Jortin, though with reluctance, acquiefces in the common opinion, that by fix unlucky lines, Virgil is destroying the beautiful fyftem, which it had coft him eight hundred to raise. He explains too this prepofterous conduct, by the ufual expedient of the poet's Epicureifm. I only differ from him in attributing to hafte and indifcretion, what he confiders as the refult of defign.

Another reason, both new and ingenious, is affigned by Dr. Jortin, for Virgil explaining away his hero's defcent into an idle dream. "All communication with the dead, the infernal powers, &c. belonged to the art Magic, and magic was held in abomination by the Romans." Yet if it was held in ABOMINATION, it was fuppofed to be real. A writer would not have made his court to James the firft, by representing the ftories of witchcraft as the phantoms of an over heated imagination.

• Whilft I am writing, a fudden thought occurs to me, which, rude and imperfect as it is, I fhall venture to throw out to the public. It is this. After Virgil, in imitation of Homer, had defcribed the two Gates of Sleep, the Horn and the Ivory, he again takes up the first in a different fenfe :

QUA VERIS FACILIS DATUR EXITUS UMBRIS.

The TRUE SHADES, VERE UMBRE, were thofe airy forms which were continually fent to animate new bodies, fuch light and almost immaterial natures as could without difficulty pafs through a thin tranfparent fubftance. In this new fenfe, Eneas and the Sybil, who were still incumbered with a load of flesh, could not pretend to the prerogative of TRUE SHADES. In their paffage over Styx, they had almost funk Charon's boat.

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Sutilis, & multam accepit rimofa paludem.

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Some other expedient was requifite for their return; and fince the Horn Gate would not afford them an eafy difmiflion, the other paffage, which was adorned with polished Ivory, was the only one that remained either for them, or for the poet. By this explanation, we fave Virgil's judgement and religion, though I muft own, at the expence of an uncommon harfhnefs and ambiguity of expreffion. Let it only be remembered, that thofe, who, in defperate cafes, conjecture with 'modefty, have a right to be heard with indulgence.'

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In this article we have been obliged to omit fome of the author's obfervations, and to abbreviate his arguments. The 'learned reader will find them exhibited to more advantage in the original; and we will venture to say, that the perufal of it will give him pleasure.

VII. The Light of Nature Purfued. By Edward Search, Efq; 3 vols. 8vo. 11. is. Payne.

THOUGH Locke, Malebranche, Leibnitz, and many others, have extended their metaphyfical enquiries through the whole compafs of the moral and intellectual world, yet nature is an inexhaustible mine; she has treasures in store which have escaped the most accurate researches, and are referved for the investigation of future ages. He who ventures into the wide fields of fpeculation, with a competent fhare of industry ́and penetration, is fure of being amply rewarded for his pains, either by the pleafing difcovery of truth, or by the beautiful fcenery, which on every fide will prefent itself to his view. He 'will always find matter fufficient for admiration, and reason to `adore the wisdom of the great Creator.

The author, whofe performance we are now confidering, is no contemptible philofopher. He has explored many of the fecret receffes of nature, and the latent principles of action, with extraordinary diligence and fagacity. And though some of his notions may be thought fingular, yet an inquifitive reader, who is fond of metaphyfical difquifitions, may attend him with pleasure and improvement through his extensive peregrinations. With respect to ourselves, we will honeftly acinowledge, that we have received infinitely more fatisfaction and entertainment from the productions of Mr. Search, than all the phyfics and metaphyfics of Aristotle.

In the introduction our author gives this account of himself, and his performance: Both believer and unbeliever will admit that there are certain truths and certain duties discoverable by our own care and fagacity, that our reafon is of fome ufe to us, and that we ought to make the best use of it in our power.

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are convertible into one another, and bodies do receive much of their activity from the particles of light, which enter their compofition; there is no body lefs apt to fhine than water; and yet water, by frequent diftillations, changes into fixed earth, which, by a fufficient heat, may be brought to fhine like other bodies. Add, that the fun and ftars, according to this great philofopher, are no other than great earths vehemently heated; for large bodies, he obferves, preserve their heat the longeft, their parts heating one another: and why may not great, denfe, and fixed bodies, when heated beyond a certain degree, emit light fo copioufly, as by the emiffion and re-action thereof, and the reflections and refractions of the rays within the pores, to grow ftill hotter, till they arrive at fuch a period of heat as is that of the fun; their parts alfo may be farther preferved from fuming away, not only by their fixity, but by the vaft weight and denfity of their atmospheres incumbent on them, and ftrongly compreffing them, and condenfing the vapours and exhalations arifing from them. Thus, we fee, warm water, in an exhaufted receiver, fhall boil as vehemently as the hottest water open to the air; the weight of the incumbent atmosphere, in this latter cafe, keeping down the vapours, and hindering the ebullition, till it has conceived its utmost degree of heat. So, alfo, a mixture of tin and lead, put on a red-hot iron in vacuo, emits a fume and flame: but the fame mixture in the open air, by reafon of the incumbent atmosphere, does not emit the leaft fenfible flame.

Upon thefe, or principles fimilar to these, the ingenious author of this performance has clearly explained the general effects of heat as relating to expanfion, fluidity, vapour, ignition, and inflammability; and after having defcribed Sir Ifaac Newton's curious method of supplying the defects of the common thermometer, very justly observes, that we cannot by that inftrument determine whether one body has double, triple, or half the heat of another body. People are apt to be mifled in this particular by the numerals; but as the lowest degree of heat is not known, we cannot abfolutely, or accurately, determine upon the heat of bodies being double, or triple, of one another. When Farenheit conftructed his thermometer, he marked the freezing point thirty-two; the lowest degree of heat which he then knew being a mixture of fal ammoniac and fnow-water, he began his fcale from it, and marked it o, being thirty-two degrees below froft. Repeated trials have fince brought the liquor in the thermometer feveral degrees below the point from whence Farenheit began his scale. Boerhaave relates with wonder and admiration a discovery of the fame Farenheit, who, with a mixture of fnow-water, and Strong

ftrong aqua-fortis, or fpirit, of nitre, brought the liquor forty degrees below o on his own fcale, that is, feventy-two degrees below the freezing point; and yet with whatever wonder the doctor is disposed to view this artificial cold produced by Farenheit, he well knew that fuch a degree of cold had been ob ferved in nature by the French philofophers, who wintered under the polar circle. In Siberia, a very cold country, and at a great distance from the fea, the mercury funk ftill more. At Kevenskoi Oftrog, on the river Lena, in Siberia, the mercury in Farenheit's thermometer fell, in 1739, to an hundred and fifty-five degrees below o; and yet, fays profeffor Ammon, who relates this remarkable depreffion in a letter to Sir Hans Sloane, animals of all kinds have furvived this cold; and although, continues he, the countries throughout which the great river Lena paffes, are exposed to fuch an extreme cold, there are, notwithstanding, the fineft, the moft rare, and moft curious plants to be found in them of any in all Siberia. The experiments made by Dr. Brown at Petersburgh, mention depreffions of the thermometer that are almoft incredible. The mercury froze in fome of the trials, and, upon breaking the thermometers, was taken out in a folid ftate, part of it serving as it were for fufpending the reft. Nay, fome experiments relate, that it was beat out to the fize of a crown-piece before it acquired its original form. One hundred and forty degrees below o on Farenheit's thermometer, feem to be the greatest depreffion for which there is any evidence, though two hundred, and even three hundred, are infifted upon. The truth is, as the mercury in fome of the experiments confeffedly froze, it muft have paffed through the range of the tube irregularly, and by starts, falling often an hundred degrees at a time; a circumftance which could not fail to involve the whole feries of experiments in uncertainty and error.

It is, fays our author, a curious question, and deferves attention, Whether heat really acts as an univerfal agent in difpofing bodies to evaporate, in the fame manner as we have feen it univerfally promote fluidity? Perhaps it would be rafh to conclude at once that all bodies are capable of being volatilized. Certain it is, there are many earths, which may, by violent heats, be rendered fluid; but have never been obferved to fuffer a diminution, in their weight, or emit any thing like vapour. But it is equally certain that we know not what is the most violent poffible degree of heat; and that, till such a degree is afcertained, it would be highly unreafonable to conclude that these earths cannot be volatilized. It was long imagined that gold and filver were perfectly fixed; and many experiments feemed to favour the opinion. Mr. Boyle put a quan

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tity of gold in the hotteft part of a glafs-houfe, and allowed it to continue there two months, at the end of which time he found the gold in a ftate of fufion, but not perceptibly dimi nified in weight. Experiments on a quantity of filver were equally void of fuccefs. The mafs of filver had, indeed, loft a little of its weight; but it was fo little, that Mr. Boyle fuppofed the diminution to be occafioned by fome impurities in the metal, which, as he imagined, had been deftroyed by the action of the fire. More recent obfervations, however, and with a more violent heat, that, viz. of the focus of a burning glafs or mirror, evidently demonftrate that gold emits team in confiderable quantities, which, when condenfed, falls down in fmall globules of that metal. What happens to the gold we may fairly infer will happen to the moft fixed bodies, comparatively speaking, provided a degree of heat, fufficient to bring them to the vaporific point, is applied. So readily, indeed, are fome philofophers for making its power in producing elastic vapour an univerfal effect of heat, that they confider every elaftic vapour as owing its existence to heat."

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In the fame judicious manner our author treats of ignition, fluidity, and other properties and effects of heat, and defcribes a great variety of experiments, which fufficiently confirm the truth of the principles he has advanced. To these are added fome excellent rules, or canons, for effecting chemical operations, and likewife an Appendix, wherein the form and ufe of the veffels, employed in conducting thofe operations, are very minutely defcribed.

IX. New-Market: Or an Essay on the Turf. Very proper to` be had in all Pockets at the next Meeting. In two Vols. 800. 50. Baldwin.

A

Satire on the diverfion of the turf, in a parallel betwixt our modern New-Market races, and the Olympic games, which were celebrated by the ancient Greeks at Elis, in Peloponnefus, every fifth year.

Let me now difcover a fecret (fays our author, in the eighty-eighth page of his first volume) which, if I had told at firft, my book had been lain down in a moment, unread; and I might have put, or rather my New-Market reader, would have put for me,

"Vestibulum ante ipfum, primoque in limine finis.

It is this, that this little treatife is lefs a comparison between New Market races and the Olympic games, than a mirror held up to vice and folly,

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