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Cxfar in the Roman calendai- ; but with tliis difference, 

 thiit, iiiftead of one day cvcvy four ytars, they iuttrpufed 

 13 days every 52 years, which produces the fame effect. 



But the moll iuterelUiig account of the rife and progrefs 

 of this fcience hitherto given, is that which is detailed by 

 M. Bailly, in his learned and elaborate hiilory of Ancient 

 and iTouem Aflronomy; in which he endeavours to trace 

 its origia among the Chaldaeans, Egyptians, Ptrfiaiis, In- 

 dians, and Chinefe, to a very early period. And in con- 

 fequence of the refearches he has made on this fubjcft, he 

 is led to maintain, that the knowledge common tg the 

 whole of thofe nations, has been derived frorn the fame 

 original fourcc ; namely, a moll anciest and highly-culti- 

 vated people of Aha, of where memory eveiy trace is now 

 extinct ; but who have been the parent-inllruclors of all 

 around them. 



M. Bailly does not pretend to fix, with certainty, the 

 prccife litualion of this ancienl people ; but he offers feveral 

 rtalons for conjecturing that it mud ha--, been fomewhere 

 about the 49th or jcth degree of nortli latitude, in the 

 fouthern regions of Siberia. Among various other coinci- 

 dences, he oblcrves, that many of the European and Afiatic 

 nations attribute their origin to that quarter, where the 

 civil and religious rites, common to each, were probably 

 firil formed ; and what he confiders as a ftrong allronomieal 

 i'npport of his hypothefis is, that the obfcrvations of the 

 liars, colleded by Ptolemy, mull have been made in a 

 climate where the longcft day was 16 hours, which corrcf- 

 ponds to the latitude here mentioned. But as that region 

 exhibits no traces of its ever having been inhabited by a 

 polilhed people, his theory, though higidy ingenious, has 

 not fufUcient force to draw our affent to his conclulions. 



In inveftigating the antiquity and progrefs of allronomy 

 among the Indians, M. Bailly examines and compares four 

 different fets of allronomieal tables of the Indian philo- 

 fophers, viz. that of the Siamefe, explained by ^I. Caffmi, 

 in 1689 ; that brought from India by M. le Gentil of the 

 Academy of Sciences ; and two other manufcript tables 

 found among the papers of the late M. de Lifle ; which, 

 he obferves, accord together, and all refer to the meridian 

 of Benares. From thcfe tables it appears, that the Indian 

 allronomy has two principal epochs, the firil being founded 

 on a conjunction of the fun, moon and planets, which is 

 laid to have taken place 3102 years before Chrill ; and the 

 other 1491 years before the fame xra. Thefe periods are 

 fo connedled by the mean motions cf the fun, moon and 

 planets, that one of them mull ncceffarily be fictitious; and 

 though the celebrated author above mentioned, has endea- 

 voured to Ihew that the firll of them mull have been founded 

 on obfcrvations, there is great reafon for believing that it 

 was rather imagined for the purpofe of giving a common 

 origin to the figns of the zodiac, and the motions ot the 

 cclcftial bodies. 



It is true indeed, if, parting from the epoch 1 491, we 

 afcend, by means of the Indian tables to the year 3102, 

 before the Chrillian a;ra, we (hall find a general conjunction 

 of the fun, moon, and planets, as thefe tables fuppofe ; but 

 this coujunftion, which is too different from the refult given 

 by the beil modern tables to have ever taken place, (hews 

 that the epoch to which they refer, is not founded upon 

 obfcrvations ; and, in fadl, fome elements of the Indian 

 allronomy, feem to indicate that they were determined even 

 long before this full epoch. The equation of the fun's 

 centre, in particular, which they fix at 2''' lo' 32", coidd 

 not, according to the calculations of M. Laplace, have been 

 of this magintude but near the year 4300 before Chrift ; 

 and befidcs this, the equatiojis of the centre of Jupiter and 



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Mars are fo different from what they ought fo have been 

 at this epoch, that nothing can be concluded from them m 

 favour of their high antiquity. 



To conclude, the whole of thefe tables, and, above all, 

 the conjundlion which they fuppofe at the fame epoch, prove, 

 on the contrary, that tliey mull have been conlhuCUd, or 

 at leall rectified, in iriuch more modern times. The ancient 

 reputation, ho\rever, of tl^e Indians, both in this and other 

 fciences, leaves but little doubt, that allronomy was calti- 

 vated among them at a very remote period ; and of this, the 

 remarkable accuracy with which they have affigncd the 

 mean motions of the fun and moon, are fufficicnt proofs, as 

 fuch exactitude could only have been obtained from a long 

 feries of obfen-ations. This opinion has alfo been ably fup- 

 ported by Mr. Playfair, in a differtation on tiie allronomy 

 of the Bramins, publiflied in the fecond volume of the tran- 

 faCtions of the Royal Society of Edinburgh, where he has, 

 likewile, adduced many inllances of their critical knowledge 

 in the other mathematical fciences, employed in their pre- 

 cepts and calculations. 



The Greeks did not begin to cultivate allronomy till a 

 long time after the Egyptians, of whom they were tlic 

 difciples ; and it is extremely difficult, amidll the fables 

 which fo much abound in the earlier periods of their hillorv, 

 to obtain any very correct information witii refpecl to their 

 knowledge in this fcience. All that we can learn is, that 

 they had made obfcrvations on the celellial bodies, and 

 divided the heavens into conftellations, 13 or 14 centuries 

 betore the Chrillian aera ; this being the period, according 

 to the opinion of the moll eminent chionologers, to whicli 

 we mull refer the fphere of Eudoxus. 



The number of their philolophical inftitutions, however, 

 afford no obferver of any note, till much later times ; moll 

 of their ancient fedls having treated allronomy as a fcience 

 purely fpeculative, without properly attending either to 

 fafts, or their caufes. But notwithftanding the reveries ia 

 which they often indulged, their knowledge began to be 

 greatly improved by Thales the Milefian, and other Greeks 

 who travelled into Egypt, and brought from thence the 

 chief principles ot the fcience. This philofopher, who died 

 at the age of 96 in the year 548 before Chrill, was the founder 

 of the Ionian left, and appears to have been the firll who 

 taught his countrymen the globular figure of the earth, the 

 obliquity of the ecliptic, and the caufes of folar and lunar 

 ecliples ; which latter phenomena he is alfo faid to have 

 been able to predict. 



Thales had for his fucceffors Anaximander, Anaximenes, 

 and Anaxagoras, to the fii'ft of whom is attributed the in- 

 vention of the gnomon, and geographical charts ; but for 

 which he was probably indebted to the Egyptians. He is 

 alfo faid lo have maintained that the fun was a mafs of fire 

 as large as the earth, which, though far below the truth 

 with relpeft to fize, was an opinion, for thofe early times, 

 that docs its author much credit ; though to him, as 

 in the cafe of Galileo, the truths he had difcovered were 

 the caufe of his perfccution. Both himfelf and his children 

 were profcribed by the Athenians, for his attempting to 

 fubjecl the works of the gods to immutable laws; and his 

 life would have paid the facrifice of his temerity, but for 

 the care of Pericles, his friend and difciple, who got his 

 ientence of death changed into exile. 



Next alter the Ionian fchool was that of Pythagoras, 

 who was born at Samos, about the year ^S6 before the 

 Chrillian sera, and who, in the celebrity he acquired, far 

 exceeded his predeceffors. Like Thales he vifited Egypt, 

 and afterwards the Brachmans of India, from whom he is 

 fuppofcd to have obtained many of the allionomical truths 



which 



