The Chaldeans, if we trust to the authority of Alba tegnius, made the sydereal year 365 days, 6 hours, and 11 minutes ; and it appears from their lunisolar periods, that their tropical year was 365 days, 5 hours, 49 minutes, and 30 seconds. Hence we have good reasons to be lieve, that they must have been acquainted with the pre cession of the equinoctial points ; a fact which they might easily have deduced from the heliacal rising and setting of the fixed stars. Aristotle informs us, that the occul tations of the planets and stars by the moon, had been frequently observed by the Chaldeans ; and we learn from Diodorus, that they considered the comets as subject to the same laws with the planetary bodies, but revolving in orbits which receded to a greater distance front the earth. From the occultations of the stars, they conjec tured that the eclipses of the sun were caused by the in terposition of the moon ; but though they seem to have been acquainted with the sphericity of the earth, they were ignorant of the cause of lunar eclipses. Dialling appears to have been known to the Chaldeans ; and so early as the 7th century before Christ, they sent to Hezekiah to inquire concerning the retrogradation of the shadow on the dial of Ahaz. Ptolemy mentions an observation upon Saturn, which was made about the year 228 A. C., the only one upon the planets which his tory has recorded; and Diodorus Siculus informs us, that the Chaldeans were acquainted with the periods of all the planets, and regarded the moon as the smallest of the heavenly bodies, and the nearest to the earth.
It is difficult to determine, with any degree of proba bility, whether astronomy was first cultivated in Egypt or Chaldea. The Egyptians, according to Diogenes Laertius, maintain, that 48,853 years elapsed between the time of Vulcan and Alexander the Great, and that during this period they had observed 373 eclipses of the sun, and 832 of the moon. These numbers represent pretty nearly the proportion between the eclipses of the two luminaries ; but Montucla and Bossut object to the credibility of this account, that the number of eclipses here mentioned might have occurred in the shorter in terval of 12 or 13 centuries. This objection, however, loses its force, when we consider that this number might indicate, not those eclipses which had actually taken place, but those which had been really observed and re corded by the Egyptians. From the heliacal rising of Syrius, the Egyptians ascertained the length of their year to be 3651 days ; and hence they discovered the So thic or canicular period of 1460 years, at the end of which the months and festivals of their civil year of 365 days returned to the same seasons. According to Ma crobius, the Egyptians were acquainted with the revolu tion of Mercury and Venus round the sun, and the or der which the planets held in the system ; and hence it is probable that Diodorus Siculus is correct in asserting, that they were also acquainted with the stations and re trogradations of the planets. Phenomena so striking as
eclipses of the sun and moon, could not fail to excite the attention of this intelligent people. Conon, the friend of Archimedes, collected many eclipses of the sun ob served by the Egyptians; and it is highly probable that they employed formula resembling those of the Indians and Siamese for computing their celestial phenomena : Thales appears to have received from the Egyptians his method of predicting an eclipse of the sun ; and Dioge nes Laertius asserts as their opinion, that the earth had a spherical form, and that the moon was eclipsed by plunging into its shadow. These facts, few and imper fect though they be, are sufficient to impress us with a high sense of the, astronomical knowledge of the Egyp tians: but whatever opinion we may entertain of the ex tent of their attainments, and the antiquity of their ob servations, we must consider that enlightened country as the hallowed Spot from which science was diffused over Europe, and as the source from which Greece de rived the most precious of her intellectual treasures.
The Persians and Phoenicians, who, from their geo graphical situation, must have had frequent intercourse with Egypt and Chaldea, seem to have drawn from these favoured kingdoms a considerable portion of astronomi cal knowledge. The year of the Persians consisted of 365 days ; and, as they were acquainted with the real period of the sun, they added an intercalary month at the end of every 120 years. This additional month fell at the close of the twelfth month after the lapse of 1440 years, which the Persians called their period of intercaladon, and which appears to have been established about 820 years before Christ. We learn from the Persian books, that there were formerly four bright stars, which point ed out the four cardinal points of the heavens ; and it is a very remarkable coincidence, in which chance could have no share, that, 'about 3000 years before the Chris tian ara, Aldebaran and Antares were situated ex actly in the two equinoctial points, while Regulus and the Southern Fish were placed in the two solstices. The zodiac of the Persians, like that of the Indians, had two divisions ; and they very strangely maintain ed, that the stars were nearer the earth than the moon : an opinion which must have preceded the observa tion of their eclipses by that luminary. While other nations were applying astronomy merely to the pur poses of agriculture and chronology, the Phoenicians were employing the stars to guide their steps through the trackless ocean, in those grand maritime enterprises which have associated their names with the earliest his tory of commercial discovery. Thus did a slender ac quaintance with the position of the Lesser Bear, enable the Phoenicians to conduct their colonies to the remotest regions of Europe, and transplant into the most savage climes the arts and sciences of the East.