[255] The hypothesis of the author is, that the excess of moisture in the orbit of Saturn, and the excess of heat in that of Mars, unite in the orbit of Jupiter and are discharged in the form of thunder. [256] Alexandre remarks, that Pliny mentions this, not as his own opinion, but that of _many_ persons; for, in chap. 21, he attempts to prove mathematically, that the moon is situated at an equal distance between the sun and the earth; Lemaire, ii. 286. [257] Marcus remarks upon the inconsistency between the account here given of Pythagoras’s opinion, and what is generally supposed to have been his theory of the planetary system, according to which the sun, and not the earth, is placed in the centre; Enfield’s Philosophy, i. 288, 289. Yet we find that Plato, and many others among the ancients, give us the same account of Pythagoras’s doctrine of the respective distances of the heavenly bodies; Ajasson, ii. 374. Plato in his Timæus, 9. p. 312-315, details the complicated arrangement which he supposes to constitute the proportionate distances of the planetary bodies. [258] Sulpicius has already been mentioned, in the ninth chapter of this book, as being the first among the Romans who gave a popular explanation of the cause of eclipses. [259] “Διὰ πασῶν, omnibus tonis contextam harmoniam.” Hardouin in Lemaire, ii. 287. [260] These appellations appear to have originated from different nations having assumed different notes as the foundation or commencement of their musical scale. The Abbé Barthelemi informs us, that “the Dorians executed the same air a tone lower than the Phrygians, and the latter a tone still higher than the Lydians; hence the denomination of the Dorian, Phrygian, and Lydian modes.” It appears to have been a general practice to employ the lowest modes for the slowest airs; Anacharsis’s Travels, iii. 73, 74. [261] Hence the passus will be equal to 5 Roman feet. If we estimate the Roman foot at 11·6496 English inches, we shall have the _miliare_ of 8 stadia equal to 1618 English yards, or 142 yards less than an English statute mile. See Adam’s Roman Antiquities, p. 503; also the articles Miliare and Pes in Smith’s Dictionary of Greek and Roman Antiquities; and for the varieties of the stadium, as employed at different periods and in different countries, see the article Stadium. The stadium which Herodotus employed in measurements of Babylon has been supposed to consist of 490 English feet, while that of Xenophon and Strabo has been estimated at 505; see Ed. Rev. xlviii. 190. The Abbé Barthelemi supposes the stadium to be equal to 604 English feet; Anach. Travels, vii. 284.