§ 12. CONSERVATIVE EFFECTS OF LAVA CURRENTS. 825 



burst through and overwhelmed sedimentary strata, and yet 

 the most delicate animal and vegetable substances remain 

 uninjured ; transmuted, indeed, into stone, but still retain- 

 ing their original structure. Thus, in the cretaceous beds 

 of Glaris, although the rock has been converted into slate 

 by intense heat, yet the fishes remain (ante, p. 353) ; the 

 strata of Monte Bolca, though capped with basalt, yet 

 swarm with ichthyolites (p. 265) ; the fiery currents of 

 Auvergne have flowed over the lacustrine limestones, and 

 still vestiges of insects, serpents, and quadrupeds, are pre- 

 served (p. 274) ; the tertiary forests of the Andes, which 

 grew on beds of lava, now lie buried beneath subsequent 

 volcanic eruptions of prodigious thickness (p. 284) ; and 

 bones either of the Dodo, or of the Solitaire, are found im- 

 bedded in sandstone, covered by lava of recent origin 

 (p. 132). 



A very remarkable circumstance is mentioned by Mr.Lyell, 

 — the preservation of a bed of ice, beneath a stream of in- 

 candescent lava. The intense heat experienced in the south 

 of Europe, during the summer and autumn of 1828, caused 

 the usual supplies of ice entirely to fail. Great distress was 

 consequently felt from the want of a commodity, regarded 

 in those countries rather as an article of necessity than of 

 luxury. Etna was, therefore, carefully explored, in the 

 hope of discovering some crevice, or natural grotto on the 

 mountain, where drift snow was still preserved. Nor was 

 the search unsuccessful ; for a small mass of perennial ice, 

 at the foot of the highest cone, was found to be part of 

 a large, continuous glacier, covered by a sheet of lava. The 

 ice was quarried, and the superposition of the lava ascer- 

 tained to continue for several hundred yards ; unfortunately, 

 the ice was so extremely hard, and the removal of it so 

 expensive, that there is no probability of the operations 

 being renewed.* Mr. Lyell explains this apparently para- 

 * Principles of Geology, vol. ii. pp. 124 — 126. 



