account of the unavoidable want of accuracy in the enumeration of the stars, or in the mode of classing them it was brought to perfection by the greeks about the time of Thales and Anaximander.

The first names given to the stars were derived from implements of husbandry, animals, useful occupations, &c. The greeks altered, augmented, or improved this nomenclature, which was in some instances rude, and in others whimsical. The rich and lively imagination, that guided all the conceptions of this ingenious people, concealed the natural dryness of the subject under pleasing and graceful images. Thus there is a constellation consisting of several stars very near together, and followed by a single star remarkable for it's brilliancy and magnitude: this groupe they called by the name of Pleiades, derived from a word signifying a multitude, and to the great star they gave that of the man Orion. The Pleiades they feigned to be the daughters of Atlas and the nymph Pleione, and Orion a giant enamoured of them, and pursuing them incessantly. Thus all the sky of the greeks was full of fabulous or historical emblems, which amused and eased the memory, without distracting the attention.

Among these constellations, those, to which the Sun, Moon, and planets answer by their true or apparent motions from west to east, occupy the space called the zodiac. This is a spherical band about sixteen degrees in breadth. Different nations have their peculiar zodiacs, that is to say, a zodiac composed of a greater or smaller number of constellations, or of more or fewer stars in each constellation.

The

most

most ancient and probable opinion is, that the zodiae of the greeks was borrowed from the egyptians; and an inscription lately found in Egypt tends to confirm this conjecture. In the time of Thales it assumed a regular form; it afterward spread throughout Europe; and we have now no other. This is divided into twelve constellations, the names and order of which from west to east are expressed in the two following

verses.

Sunt Aries, Taurus, Gemini, Cancer, Leo, Virgo,

Libraque, Scorpius, Arcitenens +, Caper |, Amphora, Pisces.

It has been disputed among the learned, whether the five planets Saturn, Jupiter, Mars, Venus, and Mercury, were known before the time of the greeks. We cannot easily suppose, that they escaped observation in the remotest ages of astronomy, or that astronomers had not acquired general ideas of their revolutions from west to east, and even of the variations which occasion them to appear sometimes stationary, sometimes direct in their motions, and at other times retrograde. But it is very doubtful whether the grecian astronomers, at the time of the first formation of their zodiac, had sufficiently accurate ideas of the inclinations of the orbits of the planets to the plane of the ecliptic, to comprise these orbits in the extent now assigned them. In fact, according to the opinion of the most learned astronomers, the first accurate observations made of the motions and

Scorpio.

+ Sagittarius.
Aquarius,

Capricornus.

appearances

appearances of Saturn, Jupiter, Mars, Venus, and Mercury, do not ascend above three centuries beyond the christian era. All the intricacies of these motions require much time and observation, to unravel and explain them in a plausible manner. Mercury, being frequently immersed in the rays of the Sun, occasioned most difficulty in this respect. It is probable, that the first zodiac of the greeks comprised only the paths of the Sun and Moon, the orbits of which cut each other at an angle of about five degrees.

We know at present that the comets are solid bodies, like the Moon and the Earth, wandering through space in all kinds of directions. The ideas of the ancients respecting the nature of these bodies were altogether erroneous: they considered them as simple meteors, which the Supreme Being made to appear from time to time, for the purpose of manifesting his displeasure, or announcing some extraordinary event. The sudden and unfrequent appearance of these comets, their irregular movements, those long tails, or trains of light, which accompany them, and display themselves in various singular forms, were terrible at first to the eye and to the imagination : every thing led a credulous and superstitious people, to consider comets as a particular class of temporary phenomena, intended by the Creator as indications of his will, which was interpreted as man thought fit. Whatever were the opinions entertained of comets by astronomers, they scarcely took the trouble to observe bodies, which, after they had appeared above the horizon for very short periods, suddenly vanished

vanished without leaving any expectation of their return. The astronomy of comets is a modern science, of which I shall speak hereafter. Here, however, justice demands me to render Seneca due homage: by an effort of philosophy superiour to the notions of his age, he did not adopt the received opinions respecting these bodies. I am not of the opinion,' says he, ‘of our philosophers: I do not consider comets as transient fires, but as one of the eternal works of nature...... Is it any wonder, that comets, so rarely as they are seen, should not yet be subjected to determinate laws; and that we do not know the beginning and end of the revolutions of these bodies, which reappear only after a long interval?..... Time and research will at length afford a solution of these problems..... The day will come, when our posterity will be astonished, that we were ignorant of truths so clear.' Nat. Quæst. lib. 7, cap. 22, 24, and 25.

The school founded by Pythagoras in Italy made astronomy a particular study. Seconded by his earliest scholars, he clearly demonstrated the sphericity of the Earth, which Anaximander had only conjectured. Having observed, that any given star appears to occupy a higher or lower station in the sky to a traveller, who goes to a place at any distance, they concluded, contrary to the testimony of the senses, that the surface of the Earth must not be a simple plane extended in a right line, but a curved and spherical superficies. Pythagoras had another idea, not less true, but much more extraordinary for the time in which he lived: he judged the Sun to be fixed in the centre of the planetary world, and the

Earth

Earth to move round it with the other planets in the celestial space: a system, which has been developed and demonstrated in modern times. But as this opinion was directly repugnant to appearance, and to the vulgar prejudices of the times, Pythagoras con-tented himself with communicating it in secret to his -scholars; whether, unable to confirm it by a sufficient number of observations, he considered it only as a very probable hypothesis; or feared, if he openly promulgated it, that he should expose himself to public derision, or even, which would be of more dangerous consequence, that he should render himself obnoxious to the persecutions of ignorance and fanaticism. In fact, these two enemies of human reason have exercised their persecuting power and despotic sway in all ages; and we need not recur to modern days, to find striking instances of it. We know, that about a hundred years after his time the philosopher Anaxagoras was accused of impiety, and condemned to banishment, for having said, that the Sun was a mass of fiery matter; and some authors add, that nothing but the influence of Pericles, his scholar and his friend, saved him from being put to death.

The measuring of time being the principal object, or rather the foundation of all astronomy, both ancients and moderns have made the greatest efforts, to determine accurately, and compare with each other, the motions of the Sun and Moon, on which thi measure universally rests.

Some imperfect observations had at first made it supposed, that the solar year consisted of 365 days:

by