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 Pythagoricians, not

These are

only the planets, but the comets themselves, are in motion round the Sun. not fleeting meteors formed in the atmo sphere, but the eternal works of nature. These opinions, so perfectly correct on the system of the universe, have been admitted and inculcated by Seneca, with the enthu→ siasm 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."

In the same school, they 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 opinions, 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.

CHAP. II.

Of Astronomy, from the Foundation of the Alexandrine School, to the Time of the Arabs.

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 some 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 positions 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 sci