73 The Canopic decree (above, p. 27) suffices to prove that the Egyptian astronomers, long before Caesar’s time, were well acquainted with the approximately exact length of the solar year, although they did not use their knowledge to correct the calendar except for a short time in the reign of Ptolemy Euergetes. With regard to Caesar’s debt to the Egyptian astronomers see Dio Cassius, xliii. 26; Macrobius, _Saturn_, i. 14. 3, i. 16. 39; L. Ideler, _Handbuch der mathematischen und technischen Chronologie_, i. 166 _sqq._ M30 Ceremonies observed in Egypt at the cutting of the dams early in August. The Bride of the Nile. Sacrifices offered by savages at the cutting of dams. 74 E. W. Lane, _Manners and Customs of the Modern Egyptians_ (Paisley and London, 1895), ch. xxvi. pp. 499 _sq._ 75 Bruno Gutmann, “Feldbausitten und Wachstumsbräuche der Wadschagga,” _Zeitschrift für Ethnologie_, xlv. (1913) pp. 484 _sq._ 76 Hon. K. R. Dundas, “Notes on the tribes inhabiting the Baringo District, East Africa Protectorate,” _Journal of the Royal Anthropological Institute_, xl. (1910) p. 54. M31 Modern Egyptian ceremony at the cutting of the dams. 77 E. W. Lane, _op. cit._ pp. 500-504; Sir Auckland Colvin, _The Making of Modern Egypt_ (London, 1906), pp. 278 _sq._ According to the latter writer, a dressed dummy was thrown into the river at each cutting of the dam. 78 Seneca, _Naturales Quaestiones_, iv. 2. 7. The cutting of the dams is mentioned by Diodorus Siculus (i. 36. 3), and the festival on that occasion (τὰ καταχυτήρια) is noticed by Eudoxus (or one of his pupils) in a passage which has already been quoted. See above, p. 35, note 2. 79 Sir Auckland Colvin, _l.c._ M32 The sowing of the seed in November. Plutarch on the mournful character of the rites of sowing. The sadness of autumn. 80 Τῆς Ἀχαίας. Plutarch derives the name from ἄχος, “pain,” “grief.” But the etymology is uncertain. It has lately been proposed to derive the epithet from ὀχή, “nourishment.” See M. P. Nilsson, _Griechische Feste_ (Leipsic, 1906), p. 326. As to the vaults (μέγαρα) of Demeter see Pausanias, ix. 8. 1; Scholiast on Lucian, _Dial. Meretr._ ii. pp. 275 _sq._, ed. H. Rabe (Leipsic, 1906). 81 In antiquity the Pleiades set at dawn about the end of October or early in November. See L. Ideler, _Handbuch der mathematischen und technischen Chronologie_, i. 242; Aug. Mommsen, _Chronologie_ (Leipsic, 1883), pp. 16, 27; G. F. Unger, “Zeitrechnung der Griechen und Römer,” in Iwan Müller’s _Handbuch der klassischen Altertumswissenschaft_, i.1 (Nördlingen, 1886) pp. 558, 585. 82 Τὰς παρουσίας τῶν ἀναγκαίων καί ἀποκρύψεις.