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what records, traditions, or circumstances, he founds his conje&ture, that the Egyptians originate from a Chinese colony, which traded on the coast of Coromandel, settled at, the place now called, Negapatnam, and carried their commercial enterprises as far as the coasts of the Red Sea.
The astronomical part of this volume is undoubtedly executed best: the Author has discovered great sagacity, industry, and knowledge, in his inquiries concerning the state of aftronomy among the Indians of the coast of Coromandel. He had great difficulties to surmount in these researches, as the kuowledge of that people is expresied in verses or allegorical symbols, 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 astronomy of the Tamoult Indians; and nothing could equal his surprit, when he saw the facility with which one of these Indians calculated, in his presence, an eclipse 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 observes) that notwithstanding the capacity which the Brahmins seem to have for aftronomical calculations, that science has not acquired among them any degree of improvement, nor made one progressive itep during the course of seven. teen centuries. It is ftill more surprising, that the Brahmins do not seem to look upon it as farther improveable by observations and experiments. This circumstance, which takes place throughout the East, has been mentioned by M. Bailli, who concluded from it, that the eastern nations were not the inventors of astronomy,- for whoever invents, is capable of im. proving, and is disposed to improve. The astronomy of the Brahmins is confined to the following five articles, -the use of the gnomon; the length of the year, the precellion of the equinoxes; the division of the Zodiac into twenty-seven constellations; and the calculation of the eclipses of the sun 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 preceflion, which the Greek philosophers only began to suspect or conjecture 128 years before the Christian æra. M. LE GENTIL also thews (and this is a discovery, at least, to us) that the ages of the world, of which the Brames or Brahmins speak, 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 years, supposing the motion of precession to be 54 annually.
The astronomical tables and observations, that take up the rest of this volume, are learned and curious, and contain a rich variety of materials for the improvement of that science. The Memoir concerning the conformity between the astronomy of the modern Brahmins and that of the ancient Chaldeans, was read to the academy of sciences in the year 1777. It unfolds the result of our Author's inquiries into the astronomical knowledge of these two nations, and concludes the firft Part of this Volume.
The second Part contains a great number of observations reJative to astronomy and natural philofophy, made principally at Pondicherry. It begins with a description of the Author's observatorv, of the instruments he used in making them, and the methods he employed to verify them. This is really a valuable collection for the astronomers, as it not only contains accurate observations, but also the results which they furnish, either for improving tables, or determining the longitudes of the different places in which they have been made. Our Author's observations on the horizontal refractions on the sea-coats, and his Table of Refractions from the horizon to the height of 90 degrees, are both curious and useful; such also are his obser: vations on the simple pendulum, and on the comet that appeare ed in 1769. There are followed by a journal of the temperature of the climate of Pondicherry, and of the variations in the seasons, as also by a description of the environs of that place, of its soil, and the different productions of the country, together with several interesting experiments on the waters that are in the neighbourhood of that city. The Supplement, which terminates this volume, contains the relation of several short voyages on the Indian feas, as also interesting remarks on the navigation from the Manila Inands to Pondicherry by the ftreights of Malacca, followed by a Memoir concerning the winds in general, the trade-winds, and the course that navi. gators ought to hold in the voyage to India after they have doubled the Cape of Good Hope. The most experienced mariners will receive satisfaction, perhaps instruction, from this part of M. LE GENTIL's Work, which must be a valuable present to all who have at heart the improvement of naviga, tion.
-Discoveries relative to Fire, Electricity, and Light, by M.
tually before our eyes, and the constant observation of its effects seems 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 hypotheses on that interesting subject. Those who have studied it with the most persevering attention and assiduity, have considered fire as an emanation from the sun, and heat as the attribute of light; but the result of curious, new, and well-conducted experiments hath enabled M. MARAT to improve, by important discoveries, this useful and entertaining branch of natural philosophy:
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 Auid, it was necessary to render it visible at the moment that it escapes with violence from the inflammable matters which it consumes, or disengages itself gently from the bodies which it has penetrated. This M. MARAT atten, ed with success, but by a method of proceeding entirely new, and by a use of the solar microscope, hitherto unknown, and which gives a new and enlarged sphere of operation to this inftrument. It is well known, that the use of the solar 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 imall objects and transparent ones can be examined by its affistance ; but by mounting it with its object-glass alone, and placing the object in a proper point of the lumi. nous cone, our Author has adapted it to the examination of objects great and small, opaque and transparent, whose emana. tions also ic renders visible.
The first thing M. MARAT attempts to prove is, that beat is nothing more than the modification of a particular fluid, and that it is the motion of this fluid, and not merely its presence, which produces heat and fire.
“ When we fix, says he, the solar microscope, mounted with
• The author of a Philosophical Elay on Man, &c. published at London in the year 1773, and of which an account was given by os.
¢ its object-glass only, to the window-shutter of a dark room, “ and place the Aame of a wax-candle in a proper part of the
cone, formed by the diverging rays of the sun, and several “ feet diftant from the focus,--then there is seen to arise on " the linen about the wick an oblong, transparent waving cy“ linder. In this cylinder the image of the fame is easily dir“ tinguished: it appears under the form of a ruddy shuttle, ” which contains, within its compass, a similar form less co“ loured, and in whose centre there shines a small point ex. “ tremely white. This cylinder is terminated by a brilliant “ stripe or border, except at its fummit, which is divided into “ several whirling, lucid particles or emisions, each furround“ ed by a smaller stripe or border. Lighted coal, red-hot iron, “ exhibit phenomena analogous to this, and lead us to conclude, “ that heat never exists, but when the igneous Auid is set in "motion.” After analysing the impression that is made on the linen, M. MARAT proves, that the brilliant elluvia 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 escapes from bodies highly heated, and is designed to communicate warmth; and that the exhalations of an enflamed or candent body are so far from trantmitting the action of the igneous fluid, that they, on the conuary, diminish and weaken it.
The properties of the igneous fiuid come next into confideration. This fluid is transparent and luminous, and its eclat or brilliancy is proportionable to its density. Hence this brilJiancy is more vivid at the borders of its sphere of activity, more especially in the centre of the fame, where the figure or form of the igneous emissions (jets) is nearly spherical. The igneous Auid is moreover a weighty body, endowed with a furprising mobility, compreslible, and not elaftic.
We refer our Readers to the Work itself for an accurate and circumstantial account of the experiments, by which our Au. thor undertakes to prove, that the igneous matter (or fire) differs essentially both from luminous matter light) and the electrical fluid. These are foilowed 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 consider the form of the sphere of activity of this Auid, and the neceflity of air to supply fire with a comprelible medium, in which it can extend freely the sphere of its activity. The experiments that illustrate this fact are intereiting and curious. Such also are his observations on the diversity which may be remarked in the power of bodies to determine the action of the igneous Auid. This diversity depends on the quantity of phlogiston, which, not being intimately united with incombustible principles, may be disengaged from them by the action of the igneous fuid.
Deflagration, and the phenomena of refrigeration, next employ the attention of our Author, who also enters into curious difu.lions relative to the light which flame diffuses, the different colours of Aame, the degrees of purity in the igneous Auid, which this diversity of colours indicates, and the causes of that fi ure of an oblong cone which Aame always afluines.
The hypothesis of M. MARAT is supported by 116 experiments ;--nevertheless we suspend our judgment, and thould be glad to see it set in a still more irresistible light. We cannot fay, that either his reasonings, 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 fhall not farther infilt upon this circumftance Еe that as it may, M. MARAT is certainly a fagacious and acute observer of nature, and poliesses all the knowledge and qualities that are requisite to make important discoveries in natural science,
X. Nouvelles Lettres d'un Vizagiur Anglois. - More Letters of an English Traveller. By M SHERLOCK. 8vo, London and Paris. 1780. HE motto at the head of this new publication of Mr.
SHERLOCK Thews, that his spirits are raised under the prospect of approaching fame. It is as follows, Incenditque animum famæ venientis amore.
VIRG. From what quarter the trun pet-bearing goddess is to make her approaches to our Author-whether or not the has already set out-or how far the may have advanced in her journey, we know not ;-neither can we guess what route the will take. If the comes through his Advice to a young Italian Poet *, this may help her on a liul in her way, and give her some propenfity to put the trumpet to her mouth in our Author's favour;- but the first Twenty Letters of an English Traveller t will probably make her take leveral iteps backward, and even think of senda in Patience in her place. The New Letters, now before us, will not, we fear, induce her to arrive, and hover, with her spread wings, over our Author's head : and yet Mr. Sherlock does not teen difpofid to put up with scanty marks of her benevolence : for the last words of his short Preface are Glory or Death
As to GLORY, we could not, in conscience, give it to him for this new publication, if we had it in our giving;
Set an a ount of this work in ar Review, vol. Ixi. p. 46o. f Şte our Keview of theie twenty Letters, ibid. p. 462.