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. Lozere_ or _Losere_) and Gabalum (_Gevaudan, Javoux_). The idolaters of Gevaudan offered cheeses to demons by throwing them into a lake on the Mons Hela.n.u.s _(Laz des h.e.l.les?_) 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 _debris_, 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 Faroe 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 erloschenen 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.]

[Footnote 154: See Professor Tyndall's _Glaciers of the Alps_, for an account of glacier-tables, sand-cones, &c. Anyone who has walked on a glacier will have noticed the little pits which any small black substance, whether a stone or a dead insect, sinks for itself in the ice.]

[Footnote 155: Gilbert, _Annalen_, lxix. 143.]

[Footnote 156: According to the latest accounts I have been able to obtain, a temperature of 2975 F. had already been reached some years ago; the temperature, a few feet from the surface, being 14 below freezing. The soil here only thaws to a depth of 3 feet in the hottest summer. Sir R. Murchison wrote to Russia, in February last, for further information regarding this well.

Since I wrote this, Sir Roderick Murchison has applied to the Secretary of the Imperial Academy of St. Petersburg for further information respecting the investigations at Jakutsk. The Secretary gives a reference to Middendorff's _Sibirische Reise_, Bd. iv. Th. i., 3te Lieferung, _Klima_, 1861. I have only been able to find the edition of 1848-51; but in that edition, under the heading _Meteorologische Beobachtungen_, elaborate tables of the meteorological condition of Jakutsk are given (i. 28-49). Also, under the heading _Geothermische Beobachtungen_, very careful information respecting the frozen earth will be found (i. 157, &c., and 178, &c.). The point at which a temperature of 32 will be attained, is reckoned variously at from 600 to 1,000 feet below the surface.]

[Footnote 157: Reise im Russischen Reich_, i. 359; St. Petersburg, 1772.]

[Footnote 158: x.x.xviii. 231 (an. 1791), in an article called _Notice mineral, de la Daourie]

[Footnote 159: L.c., p. 236.]

[Footnote 160: _Beobachtungen_, &c., 194.]

[Footnote 161: _Mundus Subterraneus_, i. 220 (i. 239, in the edition of 1678).]

[Footnote 162: 'Vidi ego in Monte Sorano cryptam veluti glacie incrustatam, ingentibus in fornice hinc inde stiriis dependentibus, e quibus vicini mentis accolae pocula aestivo tempore conficiunt, aquae vinoque quae iis infunduntur refrigerandis aptissima, extremo rigore in summas bibentium delicias commutato.']

[Footnote 163: Both here and at Schemnitz, Kircher made particular enquiries on a subject of which scientific men have altogether lost sight. At Schemnitz he asked the superintendent, _an comparcant Daemunculi vel pygmaei in fodinis?--respondit affirmative, et narrat plura exempla_; and at Herrengrund, _utrum appareant Daemunculi seu pygmaei?--respondit tales visos fuisse, et auditos pluries_. (Edition of 1678, ii. 203, 205.)]

[Footnote 164: Reich, 199.]

[Footnote 165: i. 108 (Lyon, 1794).]

[Footnote 166: _Ueber die unterirdischen Gasarten_, 101.]

[Footnote 167: xvii. 386.]

[Footnote 168: _Mem. sur les Basaltes de la Saxe_, p. 147.]

[Footnote 169: _Mineralog. Reisen_, ii. 123.]

[Footnote 170: Reich, 200, 201; Bischof, _Physical Researches on the Internal Heat of the Globe_, 46, 47.]

[Footnote 171: Peters, _Geologische und mineralogische Studien aus dem sudostlichen Ungarn_, in the _Sitzungsberichte der kais. Ak. in Wien_, B. xliii., 1te Abth., S. 435. See also pages 394 and 418 of the same volume (year 1861).]

[Footnote 172: Such ladders are in ordinary use in the Jura.]

[Footnote 173: _Turquie d'Europe,_ i. 132 (he quotes himself as i. 180, in the _Sitzungsb, der k. Ak. in Wien_, xlix. l. 324).]

[Footnote 174: L.c., p, 521.]

CHAPTER XVII.

HISTORY OF THEORIES RESPECTING THE CAUSES OF SUBTERRANEAN ICE.

The only glaciere which is in any sense historical, is that near Besancon; and a brief account of the different theories which have been advanced in explanation of the phenomena presented by it, will include almost all that has been written on ice-caves.

The first mention I have found of this cave is contained in an old history of the Franche Comte of Burgundy, published at Dole in 1592, to which reference has been already made. Gollut, the author, speaks more than once of a _glaciere_ in his topographical descriptions, and in a short account of it he states that it lay near the village of _Leugne_, which I find marked in the Delphinal Atlas very near the site of the Chartreuse of Grace-Dieu; so that there can be no doubt that his glaciere was the same with that which now exists. His theory was, that the dense covering of trees and shrubs protected the soil and the surface-water from the rays of the sun, and so the cold which was stored up in the cave was enabled to withstand the attacks of the heat of summer.[175] In the case of many of the glacieres, there can be no doubt that this idea of winter cold being so preserved, by natural means, as to resist the encroachments of the hotter seasons, is the true explanation of the phenomenon of underground ice.

The next account of this glaciere is found in the History of the Royal Academy of Sciences (French), under the year 1686,[176] but no theory is there suggested. The writer of the account states that in his time the floor of the cave was covered with ice, and that ice hung from the roof in festoons. In winter the cave was full of thick vapours, and a stream of water ran through it. The ice had for long been less abundant than in former times, in consequence of the felling of some trees which had stood near the entrance.

The Academy received in the same year another letter on this subject, confirming the previous account, and adding some particulars. From this it would seem that people flocked from all sides to the glaciere with waggons and mules, and conveyed the ice through the various parts of Burgundy, and to the camp of the Saone; not thereby diminishing the amount of ice, for one hot day produced as much as they could carry away in eight days. The ice seemed to be formed from a stream which ran through the cave and was frozen in the summer only. The writer of this second account saw vapours in the glaciere (the editor of the _Histoire de l'Academie_ does not say at what season the visit to the cave took place), and was informed that this was an infallible sign of approaching rain; so much so, that the peasants were in the habit of determining the coming weather by the state of the grotto.

In 1712, M. Billerez, Professor of Anatomy and Botany in the University of Besancon, communicated to the Academy[177] an account of a visit made by him to this cave in September 1711. He found 3 feet of ice on the floor of the cave, in a state of incipient thaw, and three pyramids, from 15 to 20 feet high and 5 or 6 feet in diameter, which had been already considerably reduced in size by thaw. A vapour was beginning to pa.s.s out from the cave, at the highest part of the arch of entrance; a phenomenon which, he was told, continued through the winter, and announced or accompanied the departure of the ice: nevertheless, the cold was so great that he could not remain in the glaciere more than half an hour with any sort of comfort. The thermometer stood at 60 outside the cave, and fell to 10[178] when placed inside; but thermometrical observations of that date were so vague as to be useless for present purposes. The ice appeared to be harder than the ordinary ice of rivers, less full of air-bubbles, and more difficult to melt.

M. Billerez enunciated a new theory to account for the phenomena presented by the cave. He observed that the earth in the immediate neighbourhood, and especially above the roof of the grotto, was full of a nitrous or ammoniac salt, and he accordingly suggested that this salt was disturbed by the heat of summer and mingled itself with the water which penetrated by means of fissures to the grotto, and so the cave was affected in the same way as the smaller vessel in the ordinary preparation of artificial ice. He had heard that some rivers in China freeze in summer from the same cause.[179]

In 1726, a further communication was made to the Academy by M. des Boz,[181] Royal Engineer, describing four visits which he had made to the grotto near Besancon at four different seasons of the year, viz., in May and November 1725, and in March and August 1726. In all cases he found the air in the cave colder than the external air,[182] and its variations in temperature corresponded with the external variations, the cold being greater in winter than in summer.

M. des Boz ascribed the existence of ice in the cave to natural causes.