CHAPTER IX. SCIENTIFIC KNOWLEDGE AMONG THE ROMANS.
The spacious level and unclouded horizon of Chaldea afforded peculiar facilities of observation; and its pastoral and contemplative inhabitants, uncontaminated by the vices and superstitions of subsequent ages, active-minded and fresh, discovered, after a long observation of eclipses - some say extending over nineteen centuries - the cycle of two hundred and twenty-three lunations, which brings back the eclipses in the same order. Having once established their cycle, they laid the foundation for the most sublime of all the sciences. Callisthenes transmitted from Babylon to Aristotle a collection of observations of all the eclipses that preceded the conquests of Alexander, together with the definite knowledge which the Chaldeans had collected about the motions of the heavenly bodies. It was rude and simple, and amounted to little beyond the fact that there were spherical revolutions about an inclined axis, and that the poles pointed always to particular stars. The Egyptians also recorded their observations, from which it would appear that they observed eclipses at least one thousand six hundred years before the commencement of our era. Nor is this improbable, if the speculations of modern philosophers respecting the age of the world are entitled to respect. The Egyptians discovered, by the rising of Sirius, that the year consists of three hundred and sixty-five and one quarter days, and this was their sacred year, in distinction from the civil, which consisted of three hundred and sixty-five days. They also had observed the courses of the planets, and could explain the phenomena of the stations and retrogradations, and it is even asserted that they regarded Mercury and Venus as satellites of the sun. Some have maintained that the obelisks which they erected served the purpose of gnomons, for determining the obliquity of the ecliptic, the altitude of the pole, and the length of the tropical year. It is thought that even the Pyramids, by the position of their sides toward the cardinal points, attest their acquaintance with a meridional line. The Chinese boast of having noticed and recorded a series of eclipses extending over a period of three thousand eight hundred and fifty-eight years, and it is probable that they anticipated the Greeks two thousand years in the discovery of the Metonic cycle, or the cycle of nineteen years, at the end of which time the new moons fall on the same days of the year. They determined the obliquity of the ecliptic, one thousand one hundred years before our era, to be 23 degrees 54' 3-15". The Indians, at a remote antiquity, represented celestial phenomena with considerable exactness, and constructed tables by which the longitude of the sun and moon are determined. Bailly thinks that astronomy was cultivated in Siam three thousand one hundred and two years before Christ, which hardly yields in accuracy to that which modern science has built on the theory of universal gravitation. The Greeks divided the heavens into constellations fourteen centuries before Christ. Thales, born 640 B.C., taught the rotundity of the earth, and that the moon shines with reflected light. He also predicted eclipses. Anaximander, born 610 B.C., invented the gnomon, and constructed geographical charts.
[The early Greek investigators.]