65. Now called _Annales des Mines_.]
[Footnote 187: T. xlv. p. 160.]
[Footnote 188: _Bibliotheque Universelle de Geneve_, Premiere Serie, t.
xx.]
[Footnote 189: See De Saussure's account of his numerous observations of
such caves in the _Voyage dans les Alpes_, sections 1404-1415.]
[Footnote 190: P. 271.]
[Footnote 191: P. 271.]
[Footnote 192: xxi. 113.]
[Footnote 193: P. 271.]
[Footnote 194: Daubuisson estimated the depth in question at from 46 to
61 feet, while Kupffer put it at 77 feet.]
[Footnote 195: De Saussure found a variation of 2 deg..25 F. at a depth of
29.5 feet; but this was in a well, where the influence of the atmosphere
was allowed to have effect. Naturally, the fissures which there may be
in the rock surrounding a cave will increase the annual variation of
temperature, by affording means of easier penetration to the heat and
cold.
Sir K. Murchison's cavern in Russia would seem to be entirely _sui
generis_.]
* * * * *
CHAPTER XVIII.
ON THE PRISMATIC STRUCTURE OF THE ICE IN GLACIERES.
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