[95] Pliny probably here refers to the opinion which Cicero puts into the mouth of one of the interlocutors in his treatise De Nat. Deor. ii. 47, “Quid enim pulchrius ea figura, quæ sola omnes alias figuras complexa continet, quæque nihil asperitatis habere, nihil offensionis potest, nihil incisum angulis, nihil anfractibus, nihil eminens, nihil lacunosum?” [96] The letter Δ, in the constellation of the triangle; it is named Δελτωτὸν by Aratus, l. 235; also by Manilius, i. 360. We may remark, that, except in this one case, the constellations have no visible resemblance to the objects of which they bear the name. [97] “Locum hunc Plinii de Galaxia, sive Lactea via, interpretantur omnes docti.” Alexandre, in Lemaire, i. 227. It may be remarked, that the word _vertex_ is here used in the sense of the astronomical term zenith, not to signify the pole. [98] De Ling. Lat. lib. iv. p. 7, 8. See also the remarks on the derivation of the word in Gesner, Thes., _in loco_. [99] “Signifer.” The English term is taken from the Greek word Ζωδιακὸς, derived from Ζῶον; see Aristotle, De Mundo, cap. 2. p. 602. The word _Zodiacus_ does not occur in Pliny, nor is it employed by Ptolemy; he names it λοξὸς κύκλος, _obliquus circulus_; Magn. Const. i. 7, 13, _et alibi_. It is used by Cicero, but professedly as a Greek term; Divin. ii. 89, and Arati Phænom. l. 317. It occurs in Hyginus, p. 57 _et alibi_, and in A. Gellius, 13. 9. Neither _signifer_ taken substantively, nor _zodiacus_ occur in Lucretius or in Manilius. [100] The account of the elements, of their nature, difference, and, more especially, the necessity of their being four, are fully discussed by Aristotle in various parts of his works, more particularly in his treatise De Cœlo, lib. iii. cap. 3, 4 and 5, lib. iv. cap. 5, and De Gener. et Cor. lib. ii. cap. 2, 3, 4 and 5. For a judicious summary of the opinions of Aristotle on this subject, I may refer to Stanley’s History of Philosophy; Aristotle, doctrines of, p. 2. l. 7, and to Enfield, i. 764 _et seq._ For the Epicurean doctrine, see Lucretius, i. 764 _et seq._ [101] Although the word _planeta_, as taken from the Greek πλανήτης, is inserted in the title of this chapter, it does not occur in any part of the text. It is not found either in Lucretius, Manilius, or Seneca, nor, I believe, was it used by any of their contemporaries, except Hyginus, p. 76. The planets were generally styled _stellæ erraticæ_, _errantes_, or _vagæ_, _sidera palantia_, as in Lucretius, ii. 1030, or simply the _five stars_, as in Cicero, De Nat. Deor. ii. 51, and in Seneca, Nat. Quæst. vii. 24. Pliny, by including the sun and moon, makes the number seven. Aratus calls them πέντ’ ἄστερες, l. 454. [102] “Aër.” “Circumfusa undique est (terra) hac animabili spirabilique natura, cui nomen est aër; Græcum illud quidem, sed perceptum jam tamen usu a nobis;” Cicero, De Nat. Deor. ii. 91.