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292 HISTORY OF GREECE. There were exaggerated statements respecting the antiquity ot their astronomical observations, which cannot be traced as of definite and recorded date higher than the era of Nabonassar 1 among the Assyrians of Babylon, as they are expressly termed by Herodo- tus uc fa-yGvai oi XaAdaiot, lovrtf ipeeg TOVTOV TOV iSeoi) (of Zeus Belus) (Ilerodot. i, 181). The Chalybcs and Chaldaei 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. 1 The earliest Chaldsean astronomical observation, known to the astrono- mer Ptolemy, both precise and of ascertained date to a degree sufficient for scientific use, was a lunar eclipse of the 19th March 721 B. c. the 27th year of the era ot Nabonassar (Ideler, Ueber die Astronomischen Beobach- tungcn der Alten, p. 19, Berlin, 1806). Had Ptolemy known any older ob- servations conforming to these conditions, he would not have omitted to notice them : his own words in the Almagest testify how much he valued tho knowledge and comparison of observations taken at distant intervals (Alma- gest, b. 3, p. 62, ap. Ideler, I. c. p. 1), and at the same time imply that he had none more ancient than the era of Nabonassar (Aim. iii, p. 77, ap. Idel. p. 169). That the Chaldaeans had been, long before this period, in the habit of ob serving the heavens, there is no reason to doubt ; and the exactness of those observations cited by Ptolemy implies (according to the judgment of Ideler ib. p. 167) long previous practice. The period of two hundred and twenty- three lunations, after which the moon reverts nearly to the same positions in reference to the apsides and nodes, and after which eclipses return nearly in the same order and magnitude, appears to have been discovered by the Chal- dseans (" Defectus ducentis viginti tribus mensibus redire in suos orbes certum est," Pliny, H. N. ii, 13), and they deduced from hence the mean daily mo- tions of the moon with a degree of accuracy which differs only by four seconds from modern lunar tables (Gemiuus, Isagoge in Arati Phaenomcna, c. 15; Ideler, 1. c. pp. 153, 154, and in his Handbuch der Chronologic, vol. i, Absch. ii, p. 207). There seem to have been Chaldajan observations, both made and recorded, of much greater antiquity than the era of Nabonassar ; though we cannot lay much stress on the date of 1903 years anterior to Alexander the Great, which is mentioned by Simplicius (ad Aristot. de Ccelo, p. 123) as being the earliest period of the Chaldsean observations sent from Babylon by Kallis- thenes to Aristotle. Ideler thinks that the Chaldrean observations anterior to the era of Nabonassar were useless to astronomers from the want of some fixed era, or definite cycle, to identify the date of each of them. The com- mon civil year of the Chalda;ans had been from the beginning (like that of the Greeks) a lunar year, kept in a certain degree of harmony with the sun by cycles of lunar years and intercalation. Down to the era of Nabonassar, the calender was in confusion, and there was nothing to verify either the time