I agree with Volney (Chronologie des Babyloniens, ch. x, p. 215) in thinking this statement both unsupported and improbable. Mannert seems to suppose the Chaldæans of Arabian origin (Geogr. der Gr. und Röm., part v, s. 2, ch. xii, p. 419). The passages of Strabo (xvi, p. 739) are more favorable to this opinion than to that of Heeren; but we make out nothing distinct respecting the Chaldæans except that they were the priestly order among the Assyrians of Babylon, as they are expressly termed by Herodotus—ὡς λέγουσι οἱ Χαλδαῖοι, ἐόντες ἱρέες τούτου τοῦ θεοῦ (of Zeus Bêlus) (Herodot. i, 181). The Chalybes and Chaldæi of the northern mountains seem to be known only through Xenophon (Anab. iv, 3, 4; v, 5, 17; Cyrop. iii, 2, 1); they are rude barbarians, and of their exploits or history no particulars reach us. There were exaggerated statements respecting the antiquity of their astronomical observations, which cannot be traced as of definite and recorded date higher than the era of Nabonassar[554] (747 B. C.), as well as respecting the extent of their acquired knowledge, so largely blended with astrological fancies and occult influences of the heavenly bodies on human affairs. But however incomplete their knowledge may appear when judged by the standard of after-times, there can be no doubt, that compared with any of their contemporaries of the sixth century B. C.—either Egyptians, Greeks, or Asiatics—they stood preëminent, and had much to teach, not only to Thalês and Pythagoras, but even to later inquirers, such as Eudoxus and Aristotle. The conception of the revolving celestial sphere, the gnomon, and the division of the day into twelve parts, are affirmed by Herodotus[555] to have been first taught to the Greeks by the Babylonians; and the continuous observation of the heavens both by the Egyptian and Chaldæan priests, had determined with considerable exactness both the duration of the solar year and other longer periods of astronomical recurrence; thus impressing upon intelligent Greeks the imperfection of their own calendars, and furnishing them with a basis not only for enlarged observations of their own, but also for the discovery and application of those mathematical theories whereby astronomy first became a science.