astronomy is lost in the darkness which envelops the origin of these people. In no country do they go back so far as in China, by an incontestable series of historical monuments.

The prediction of eclipses, and the regulation of the calendar, were always regarded as important objects, for which a mathematical tribunal was established; but the scrupulous attachment of the Chinese to ancient customs, which extended even to their astronomical rules, has contributed among them to keep this science in a perpetual state of infancy.

The Indian tables indicate a much more refined astronomy; but every thing shows that it is not of an extremely remote antiquity. And here, with regret, I differ in opinion from a learned and illustrious astronomer, who, after having honoured his career by labours useful both to science and humanity, fell a victim to the most sanguinary tyranny, opposing the calmness and dignity of virtue to the revilings of an infatuated people, who wantonly prolonged the last agonies of his existence*.

æra.

The Indian tables have two principal epochs, which go back, one to the year 3102, the other to the year 1491 before the Christian These epochs are connected with the mean motions of the sun, moon, and planets, in such a manner, that one is evidently fictitious; the celebrated astronomer, above alluded to, endeavours, in his Indian astronomy, to prove, that the first of these epochs is founded on observation. Notwithstanding all the arguments are brought forward with that interest he so well knew how to bestow on subjects the most difficult, I am still of opinion, that this period was invented for the purpose of giving a common origin to all the motions of the heavenly bodies in the zodiac. In fact, computing, according to the Indian tables, from the year 1491, to 3102, we find a general conjunction of the sun and all the planets, as these tables suppose, but their conjunction differs too much from the result of our best tables to have ever taken place, which shows that the epoch to which they refer, was not established on observation. But, it must be owned, that some elements of the Indian astronomy seem to indicate that they have been determined even

* Lavoisier, the great founder of the nomenclature of modern chemistry. He was born at Paris, Aug. 26, 1743, and was guillotined May 8, 1794, during the tyranny of Robespierre.-Editor

before this first epoch. Thus the equation of the centre of the sun, which they fix at 20.4173, could not have been of that magnitude; but at the year 4300 before the Christian æra. But, independently of the errors to which the Indian observations are liable, it may be observed, that they only considered the inequalities of the sun and moon, relative to eclipses, in which the annual equation of the moon is added to the equation of the centre of the sun, and augments it about * 22′, which is very nearly the difference between our determinations and those of the Indians. Many elements, such as the equations of the centre of Jupiter and Mars, are so different in the Indian tables, from what they must have been at their first epoch, that we can conclude nothing in favour of their antiquity from the other elements.

The whole of these tables, particularly the impossibility of the conjunction, at the epoch they suppose, prove on the contrary, that they have been constructed, or at least rectified in modern times. Nevertheless, the ancient reputation of the Indians does not permit us to doubt, that they have always cultivated astronomy, and the remarkable exactness of the mean motions which they have assigned to the sun and moon, necessarily required very ancient obser

vations.

The Greeks did not begin to cultivate astronomy till a long time after the Egyptians, of whom they were the disciples.

It is extremely difficult to ascertain the exact state of their astronomical knowledge, amidst the variety of fable which fills the early part of their history. It appears, however, that they divided the heavens into constellations, about thirteen or fourteen centuries before the Christian æra; for it is to this epoch that the sphere of Eudoxus should be referred. Their numberless schools for philosophy produced not one single observer before the foundation of the Alexandrine school. They treated astronomy as a science purely speculative, often indulging in the most frivolous conjectures.

It is singular, that at the sight of so many contending systems, which taught nothing, the simple reflection, that the only method of comprehending nature is to interrogate her by experiment, never occurred to one of these philosophers, though so many were en

* 11' 52".

dowed with an admirable genius. But we must reflect, that the first observation only presenting insulated facts, little suited to attract the imagination, impatient to ascend to causes, they must have succeeded each with extreme slowness. It required a long succession of ages to accumulate a sufficient number, to discover, among the various phenomena, such relations, which, by extending themselves, should unite with the interest of truth, that of such general speculations as the human understanding delights to indulge in.

Nevertheless, in the philosophic dreams of Greece, we trace some sound ideas, which their astronomers collected in their travels, and afterwards improved. Thales, born at Miletus, 640 years before our æra, went to Egypt for instruction: on his return to Greece, he founded the Ionian school, and there taught the sphericity of the earth, the obliquity of the ecliptic, and the true causes of the eclipses of the sun and moon; he even went so far as to predict them, employing, no doubt, the periods which had been communicated to him by the priests of Egypt.

Thales had for his successors- -Anaximander, Anaximenes, and Anaxagoras; to the first is attributed the invention of the gnomon and geographical charts, which the Egyptians appear to have been already acquainted with.

Anaxagoras was persecuted by the Athenians for having taught these truths of the Ionian school. They reproached him with having destroyed the influence of the gods on nature, by endeavouring to reduce phenomena to immutable laws. Proscribed with his children, he only owed his life to the protection of Pericles, his disciple and his friend, who succeeded in procuring a mitigation of his sentence from death to banishment. Thus, truth, to establish itself on earth, has almost always had to combat established prejudices, and has more than once been fatal to those who have discovered it. From the Ionian school arose the chief of one more celebrated. Pythagoras, born at Samos, about 590 years before Christ, was at first the disciple of Thales. This philosopher advised him to travel into Egypt, where he consented to be initiated into the mysteries of the priests, that he might obtain a knowledge of all their doctrines. The Brachmans having then attracted his curiosity, he went to visit them, as far as the shores of the Ganges. On his return to his own country, the despotism under which it groaned, obliged him again to quit it, and he retired to Italy, where he

founded his school. All the astronomical truths of the Ionian school, were taught on a more extended scale in that of Pythagoras; but what principally distinguished it, was the knowledge of the two motions of the earth on itself, and about the sun. Pythagoras carefully concealed this from the vulgar, in imitation of the Egyptian priests, from whom, most probably, he derived his knowledge; but his system was more fully explained, and more openly avowed by his disciple Philalaus.

According to the Pythagorists, not only the planets, but the comets themselves, are in motion round the sun. These are not fleeting meteors formed in the atmosphere, but the mighty works of nature. These opinions, so perfectly correct on the system of the universe, have been admitted and inculcated by Seneca, with the enthusiasm which a great idea, on the subject the most vast of human contemplation, naturally excited in the soul of a philosopher.

"Let us not wonder," says he, " that we are still ignorant of the law of the motion of comets, whose appearance is so rare, that we neither can tell the beginning nor the end of the revolution of these bodies, which descend to us from an immense distance. It is not fifteen hundred years since the stars have been numbered in Greece, and names given to the constellations. The day will come, when, by the continued study of successive ages, things which are now hid, will appear with certainty, and posterity will wonder they have escaped our notice.

The same school taught that the planets were inhabited, and that the stars were suns disseminated in space, being themselves centres of planetary systems. These philosophic views should, from their grandeur and justness, have obtained the suffrages of antiquity; but having been taught with systematic speculations, such as the harmony of the heavenly spheres, and wanting, moreover, that proof which has since been obtained, by the agreement with observations, it is not surprising that their truth, when opposed to the illusions of the senses, should not have been admitted.

[La Place, Exposition du Systême du Monde.]

CHAP. II.

ASTRONOMY OF THE SCHOOL OF ALEXANDRIA.

HITHERTO the practical astronomy of different people has

only offered us some rude observations relative to the seasons and eclipses; objects of their necessities or their terrors. Their theoretical astronomy consisted in the knowledge of some periods, founded on very long intervals of time, and of various fortunate conjectures, relative to the constitution of the universe, but mixed with considerable error. We see, for the first time, in the school of Alexandria, a connected series of observations; angular distances were made with instruments suitable to the purpose, and they were calculated by trigometrical methods. Astronomy then took a new form, which the following ages have adopted and brought to perfection. The posititions of the fixed stars were determined, the paths of the planets carefully traced, the inequalities of the sun and moon were better known, and, finally, it was the School of Alexandria that gave birth to the first system of Astronomy, that had ever comprehended an entire plan of the celestial motions. This system was, it must be allowed, very inferior to that of the school of Pythagoras, but being founded on a comparison of observations, it afforded, by this very comparison, the means of its own destruction, and the true system of nature has been elevated on its ruins.

After the death of Alexander, his principal generals divided his empire among themselves, and Ptolemy Soter received Egypt for his share. His munificence and love of the sciences, attracted to Alexandria the capital of his kingdom, a great number of the most learned men of Greece. Ptolemy Philadelphus, who inherited with the kingdom his father's love of the sciences, established them there under his own particular protection. A vast edifice, in which they were lodged, contained both an observatory, and that magnificent library which Demetrius Phalereus had collected with immense trouble and expense. Here they were supplied with whatever books and instruments were necessary to their pursuits; and their emulation was excited by the presence of a prince, who often came amongst them to participate in their conversation and their labours. Arystillus and Timochares were the first observers of the rising