[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.
[103] “universi cardine.” “Revolutionis, ut aiunt, centro. Idem Plinius, hoc ipso libro, cap. 64, terram cœli cardinem esse dicit;” Alexandre, in Lem. i. 228. On this subject I may refer to Ptolemy, Magn. Const, lib. i. cap. 3, 4, 6. See also Apuleius, near the commencement of his treatise De Mundo.
[104] “Sidera.” The word sidus is used, in most cases, for one of the heavenly bodies generally, sometimes for what we term a constellation, a particular assemblage of them, and sometimes specially for an individual star. Manilius employs the word in all these senses, as will appear by the three following passages respectively; the first taken from the opening of his poem,
“Carmine divinas artes, et conscia fati
Sidera....”
The second,
“Hæc igitur texunt æquali sidera tractu
Ignibus in varias cœlum laqueantia formas.” i. 275, 276.