[653] Aristotle, Strabo, and Silius Italicus, viii. 582, 583, refer to this property of the Silarus; but, according to Brotier, it does not appear to be known to the present inhabitants of the district through which it flows. Lemaire, i. 440. [654] In a subsequent part of the work, xxxi. 8, our author remarks, “Reatinis tantum paludibus ungulas jumentorum indurari.” We may presume that the water contained some saline, earthy or metallic substance, either in solution, or in a state of minute division, which would produce these effects. It does not appear that anything of this kind has been observed by the moderns in this water. [655] The coral beds with which the Red Sea abounds may have given rise to this opinion: see the remarks of Alexandre _in loco_. Hardouin informs us, that this clause respecting the Red Sea is not found in any of the MSS. Lemaire, i. 441. A similar observation occurs in a subsequent part of the work, xiii. 48. [656] There are thermal springs in the Alpine valleys, but not any in the elevated parts of the Alps themselves. [657] The volcanic nature of a large portion of the south of Italy and the neighbouring islands may be regarded as the cause of the warm springs which are found there. [658] This river may be supposed to have been principally supplied by melted snow; it would appear to be colder, because its temperature would be less elevated than the other streams in the neighbourhood. [659] The statement, if correct, may be referred to the discharge of a quantity of inflammable gas from the surface of the water. The fact is mentioned by Lucretius, vi. 879, 880, and by Mela. [660] “Quasi alternis requiescens, ac meridians: diem diffindens, ut Varro loquitur, insititia quiete.” Hardouin in Lemaire, i. 443. He says that there is a similar kind of fountain in Provence, called Collis Martiensis. [661] There has been considerable difference of opinion among the commentators, both as to the reading of the text and its interpretation, for which I shall refer to the notes of Poinsinet, i. 307, of Hardouin and Alexandre, Lemaire, i. 443, and of Richelet, Ajasson, ii. 402. [662] We have an account of the Troglodytæ in a subsequent part of the work, v. 5. The name is generally applied by the ancients to a tribe of people inhabiting a portion of Æthiopia, and is derived from the circumstance of their dwellings being composed of caverns; a τρωγλὴ and δύνω. Alexandre remarks, that the name was occasionally applied to other tribes, whose habitations were of the same kind; Lemaire, i. 443. They are referred to by Q. Curtius as a tribe of the Æthiopians, situated to the south of Egypt and extending to the Red Sea, iv. 7. [663] Q. Curtius gives nearly the same account of this fountain.