[Footnote 139: See many careful descriptions of these caves in the _Annales de Chimie_; also, an account by Professor Ansted, in his _Science, Scenery, and Art_, p. 29. M. Chaptal (_Ann. de Chimie_, iv. 34) found the lowest temperature of the currents of cold air to be 36º·5 F.; but M. Girou de Buzareingues _(Ann. de Chimie et de Phys_., xlv. 362) found that with a strong north wind, the temperature of the external air being 55º·4 F., the coldest current gave 35º·6 F.; with less external wind, still blowing from the north, the external air lost half a degree centigrade of heat, while the current in the cave rose to 38º·75 F. The cellars in which the famous cheese of Roquefort is ripened are not subterranean, but are buildings joined on to the rock at the mouths of the fissures whence the currents proceed. They are so valuable, that one, which cost 12,000 francs in construction, sold for 215,000 francs. The cheese of this district has had a great reputation from very early times. Pliny (_Hist. Nat_. xi. 97) mentions, with commendation, the cheeses of Lesura (_M. Lozère_ or _Losère_) and Gabalum (_Gevaudan, Javoux_). The idolaters of Gevaudan offered cheeses to demons by throwing them into a lake on the Mons Helanus _(Laz des Helles?_) and it was not till the year 550 that S. Hilary, Bishop of Mende, succeeded in putting a stop to this practice.] [Footnote 140: It would seem from his own account of the Sauberg, and from the description given above of the presence of ice among the rocky _débris_, as well as from the account on this page of ice in Virginia, that a formation of loose stones is favourable to the existence of a low degree of temperature. See also the note on p. 263, with respect to the loose stones near Les Plans. Forchhammer found, on the Faroë Islands, that springs which rise from loose stones are invariably colder than those which proceed from more solid rock at the same elevation, as indeed might have been expected.] [Footnote 141: xvii. 337. The account is taken from a Dutch journal.] [Footnote 142: xix. p. 124.] [Footnote 143: October 11, 1829.] [Footnote 144: viii. 254.] [Footnote 145: Pp. 174-6.] [Footnote 146: Thermometer about 85° F.] [Footnote 147: v. 154.] [Footnote 148: iv. 300.] [Footnote 149: _Die erlöschenen Vulkane in der Eifel_, S. 59.] [Footnote 150: Dr. Gmelin, of Tubingen, detected the presence of ammonia both in clinkstone lava and in columnar basalt (_American Journal of Science_, iv. 371).] [Footnote 151: _Geology and Extinct Volcanoes of Central France_, p. 60 (second edition).] [Footnote 152: Mr. William Longman has informed me that some years ago he had ice given him in summer, when he was on a visit to the inspector of mines at Pont Gibaud, and he was told that it was formed in a neighbouring cavern during the hot season.] [Footnote 153: Original edition of 1830, i. 369.]