[151] The division of the planets into superior and inferior was not known to Aristotle, De Mundo, cap. ii. p. 602, to Plato, Timæus, p. 318, 319, or the older Greek astronomers. It was first made by the Egyptians, and was transferred from them to the Romans. It is one of the points in which our author differs from Aristotle. See the remarks of Marcus in Ajasson, ii. 242 _et seq._ Marcus notices the various points which prove the deficiency of Pliny’s knowledge of astronomy; he particularizes the four following:—his ignorance of the true situation of the constellations; his erroneous opinion respecting the cause of the seasons; his account of the phases of the moon, and of the position of the cardinal points. He appears not to have been aware, that certain astronomical phænomena undergo a regular progression, but supposed that they remained, at the time when he wrote, in the same state as in the age of Hipparchus or the original observers. Columella, when treating on these subjects, describes the phænomena according to the ancient calculation, but he informs us, that he adopts it, because it was the one in popular use, and better known by the farmers (De Re Rust. ix. 14), while Pliny appears not to have been aware of the inaccuracy. [152] “Modo solem antegrediens, modo subsequens.” Hardouin in Lemaire, ii. 243. [153] It was not known to the earlier writers that Lucifer and Vesper were the same star, differently situated with respect to the Sun. Playfair remarks, that Venus is the only planet mentioned in the sacred writings, and in the most ancient poets, such as Hesiod and Homer; Outlines, ii. 156. [154] There has been much discussion among the commentators respecting the correctness of the figures in the text; according to the æra of the olympiads, the date referred to will be between the years 750 and 754 B.C.; the foundation of Rome is commonly referred to the year 753 B.C. See the remarks of Marcus in Ajasson, ii. 278, 9. [155] Aristotle informs us, that it was called either Phosphorus, Juno, or Venus; De Mundo, cap. 2. t. i. p. 602. See also Hyginus, Poet. Astr. lib. iii. p. 76, 7; and Apuleius, De Mundo, § 710. [156] It will be scarcely necessary to refer the reader to the well-known commencement of Lucretius’s poem for the illustration of this passage; it is remarkable that Pliny does not refer to this writer. [157] The periodical revolution of Venus is 224·7 days, see note [142], p. 27. Its greatest elongation is 47° 1′; Somerville, § 641. p. 391.