[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 29·75° 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: xxxviii. 231 (an. 1791), in an article called _Notice minéral, 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 accolæ pocula æstivo tempore conficiunt, aquæ vinoque quæ 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 Dæmunculi vel pygmæi in fodinis?--respondit affirmative, et narrat plura exempla_; and at Herrengrund, _utrum appareant Dæmunculi seu pygmæi?--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: _Mém. 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.]