[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.