what records, traditions, or circumftances, he founds his conjecture, that the Egyptians originate from a Chinese colony, which traded on the coaft of Coromandel, fettled at, the place now called, Negapatnam, and carried their commercial enterprifes as far as the coafts of the Red Sea.

The aftronomical part of this volume is undoubtedly executed beft: the Author has difcovered great fagacity, industry, and knowledge, in his inquiries concerning the fate of aftronomy among the Indians of the coaft of Coromandel. He had great difficulties to furmount in these researches, as the knowledge of that people is expressed in verfes or allegorical fymbols, and the explication of the characters is often difficult, and doubtful, on account of the incapacity of the interpreters. The curiofity of M. LE GENTIL was excited by the accounts he had heard, at Pondicherry, of the aftronomy of the Tamoult Indians; and nothing could equal his furprife, when he faw the facility with which one of thefe Indians calculated, in his prefence, an eclipfe of the moon (which he had proposed to him) with all the preliminary elements of that phenomenon, in three quarters of an hour. It is very fingular (as our Author obferves) that notwithstanding the capacity which the Brahmins feem to have for aftronomical calculations, that fcience has not acquired among them any degree of improvement, nor made one progreffive ftep during the courfe of feventeen centuries. It is ftill more furprifing, that the Brahmins do not feem to look upon it as farther improveable by obfervations and experiments. This circumftance, which takes place throughout the Eaft, has been mentioned by M. Bailli, who concluded from it, that the eastern nations were not the inventors of aftronomy,- for whoever invents, is capable of improving, and is difpofed to improve. The aftronomy of the Brahmins is confined to the following five articles,-the use of the gnomon; the length of the year; the preceffion of the equinoxes; the divifion of the Zodiac into twenty-feven conftellations; and the calculation of the eclipfes of the fun and moon, It appears from our Author's account of the tropical year of the Brahmins, and their calculations of the preceffion of the equinoxes, that the Indians had a more accurate knowledge of the length of the year, than that which has been transmitted to us by Ptolemy and Hipparchus ; and our Author concludes from hence, that they were acquainted with the motion of preceffion, which the Greek philofophers only began to fufpect or conjecture 128 years before the Chriftian æra. M. LE GENTIL allo fhews (and this is a difcovery, at least, to us) that the ages of the world, of which the Brames or Brahmins fpeak, are no more than a revolution of the heavens, or the period of the motion of the stars in longitude, which is a period of

3

24,000

24,000 years, fuppofing the motion of preceffion to be 54 annually.

The aftronomical tables and obfervations, that take up the rest of this volume, are learned and curious, and contain a rich variety of materials for the improvement of that fcience. The Memoir concerning the conformity between the aftronomy of the modern Brahmins and that of the ancient Chaldeans, was read to the academy of fciences in the year 1777. It unfolds the refult of our Author's inquiries into the aftronomical knowledge of these two nations, and concludes the first Part of this Volume.

The fecond Part contains a great number of observations relative to aftronomy and natural philofophy, made principally at Pondicherry. It begins with a defcription of the Author's obfervatory, of the inftruments he ufed in making them, and the methods he employed to verify them. This is really a valuable collection for the aftronomers, as it not only contains accurate, obfervations, but also the refults which they furnish, either for. improving tables, or determining the longitudes of the different places in which they have been made. Our Author's obfervations on the horizontal refractions on the fea-coafts, and his Table of Refractions from the horizon to the height of go degrees, are both curious and useful; fuch also are his obfervations on the fimple pendulum, and on the comet that appeared in 1769. Thefe are followed by a journal of the temperature of the climate of Pondicherry, and of the variations in the feafons, as alfo by a defcription of the environs of that. place, of its foil, and the different productions of the country, together with feveral interefting experiments on the waters that are in the neighbourhood of that city. The Supplement, which terminates this volume, contains the relation of feveral fhort voyages on the Indian feas, as alfo interefting remarks on the navigation from the Manila Ilands to Pondicherry by the ftreights of Malacca, followed by a Memoir concerning the winds in general, the trade-winds, and the courfe that navigators ought to hold in the voyage to India after they have doubled the Cape of Good Hope. The most experienced mariners will receive fatisfaction, perhaps inftruction, from this part of M. LE GENTIL'S Work, which must be a valuable, present to all who have at heart the improvement of navigation.

ART.

Decouvertes de M. Marat, fur le Feu, l'Ele@ricité, et la Lumiere, &c. -Discoverics relative to Fire, Electricity, and Light, by M. MARAT, M. D. Phyfician to the Life-Guards of the Count d'Artois, confirmed by a feries of Experiments, which have been repeated and verified by Commiffaries, appointed by the Royal Academy of Sciences, for that Purpose. 8vo. Paris. 1779.

Tis fingular enough, that though fire is an object perpe

effects feems to facilitate the means of arriving at the knowledge of its nature, we have hitherto got little farther than the formation of ingenious conjectures and hypothefes on that interesting fubject. Thofe who have ftudied it with the most perfevering attention and affiduity, have confidered fire as an emanation from the fun, and heat as the attribute of light; but the refult of curious, new, and well-conducted experiments hath enabled M. MARAT to improve, by important discoveries, this useful and entertaining branch of natural philofophy,

From an attentive confideration of the known phenomena, our Author concluded, that heat and fire are modifications of the motion of a particular fluid; but to know the nature of this fluid, it was neceffary to render it vifible at the moment that it efcapes with violence from the inflammable matters which it confumes, or difengages itfelf gently from the bodies which it has penetrated. This M. MARAT attempted with fuccefs, but by a method of proceeding entirely new, and by a ufe of the folar microfcope, hitherto unknown, and which gives a new and enlarged fphere of operation to this inftrument. It is well known, that the use of the folar microscope has been hitherto confined within narrow bounds. By the ordinary manner of employing it, the object is placed in the focus, and thus only fmall objects and transparent ones can be examined by its affiftance; but by mounting it with its object-glafs alone, and placing the object in a proper point of the luminous cone, our Author has adapted it to the examination of objects great and fmall, opaque and tranfparent, whofe emanations alfo it renders vifible.

The first thing M. MARAT attempts to prove is, that heat is nothing more than the modification of a particular fluid, and that it is the motion of this fluid, and not merely its prefence, which produces heat and fire.

"When we fix, fays he, the folar microfcope, mounted with

The author of a Philofophical Effay on Man, &c. published at London in the year 1773, and of which an account was given by us.

its object-glafs only, to the window-fhutter of a dark room, and place the flame of a wax-candle in a proper part of the cone, formed by the diverging rays of the fun, and feveral feet diftant from the focus,-then there is feen to arife on "the linen about the wick an oblong, tranfparent waving cylinder. In this cylinder the image of the flame is eafily dif "tinguished: it appears under the form of a ruddy fhuttle, "which contains, within its compafs, a fimilar form lefs co"loured, and in whofe centre there fhines a fmall point ex"tremely white. This cylinder is terminated by a brilliant "ftripe or border, except at its fummit, which is divided into "feveral whirling, lucid particles or emiffions, each furround"ed by a fmaller ftripe or border. Lighted coal, red-hot iron, "exhibit phenomena analogous to this, and lead us to conclude, "that heat never exifts, but when the igneous fluid is fet in "motion." After analyfing the impreffion that is made on the linen, M. MARAT proves, that the brilliant effluvia obfervable on the linen or paper that is employed in the experiment, are properly portions or undulations of the igneous fluid itself, and not a fort of light vapour, which efcapes from bodies highly heated, and is defigned to communicate warmth; and that the exhalations of an enflamed or candent body are so far from transmitting the action of the igneous fluid, that they, on the contrary, diminifh and weaken it.

The properties of the igneous fluid come next into confideration. This fluid is tranfparent and luminous, and its eclat or brilliancy is proportionable to its denfity. Hence this brilliancy is more vivid at the borders of its fphere of activity, more especially in the centre of the flame, where the figure or form of the igneous emiffions (jets) is nearly fpherical. The igneous fluid is moreover a weighty body, endowed with a furprifing mobility, compreffible, and not elaftic.

We refer our Readers to the Work itself for an accurate and circumftantial account of the experiments, by which our Author undertakes to prove, that the igneous matter (or fire) differs effentially both from luminous matter (light) and the electrical fluid. Thefe are followed by other experiments, which indicate the laws and properties of the motion of the igneous fluid, when its action is excited. From hence M. MARAT proceeds to confider the form of the fphere of activity of this fluid, and the neceffity of air to fupply fire with a compreflible medium, in which it can extend freely the fphere of its acuvity. The experiments that illuftrate this fact are interefting and curious. Such alfo are his obfervations on the diverfity. which may be remarked in the power of bodies to determine the action of the igneous fluid. This diverfity depends on the quantity of phlogifton, which, not being intimately united

with

with incombustible principles, may be difengaged from them by the action of the igneous fluid.

Deflagration, and the phenomena of refrigeration, next employ the attention of our Author, who alfo enters into curious difcuffions relative to the light which flame diffuses, the different colours of flame, the degrees of purity in the igneous fluid, which this diverfity of colours indicates, and the caufes of that figure of an oblong cone which flame always affumes.

The hypothefis of M. MARAT is fupported by 116 experiments; nevertheless we fufpend our judgment, and should be glad to fee it fet in a still more irrefiftible light. We cannot fay, that either his reafonings, or the account of his experiments, are free from all charge of obfcurity; at least, we have not found them fo.-This however may be our fault, and therefore we shall not farther infift upon this circumftance. Be that as it may, M. MARAT is certainly a fagacious and acute obferver of nature, and poffeffes all the knowledge and qualities that are requifite to make important difcoveries in natural fcience.

ART. X.

Nouvelles Lettres d'un Voyageur Anglois.-More Letters of an English Traveller. By M. SHERLOCK. 8vo. London and Paris. 1780.

TH

HE motto at the head of this new publication of Mr. SHERLOCK fhews, that his fpirits are raised under the profpect of approaching fame. It is as follows,

Incenditque animum fame venientis amore.

VIRG.

From what quarter the trumpet-bearing goddess is to make her approaches to our Author-whether or not fhe has already fet out-or how far fhe may have advanced in her journey, we know not ;-neither can we guess what route fhe will take. If fhe comes through his Advice to a young Italian Poet*, this may help her on a little in her way, and give her fome propenfity to put the trumpet to her mouth in our Author's favour;-but the first Twenty Letters of an English Traveller + will probably make her take feveral fteps backward, and even think of fending Patience in her place. The New Letters, now before us, will not, we fear, induce her to arrive, and hover, with her fpread wings, over our Author's head and yet Mr. Sherlock does not feem difpofed to put up with fcanty marks of her benevolence for the laft words of his fhort Preface are Glory or Death. As to GLORY, we could not, in confcience, give it to him for this new publication, if we had it in our giving;—

• See an account of this work in our Review, vol. Ixi. p. 460. + See our Review of thefe twenty Letters, ibid. p. 462.

and