The Cave of Yermalik, already mentioned among the silent retreats of nature which have been rendered infamous by the cruelty of man, is likewise highly interesting as a natural glacière. After leaving the roomy dome in which they found the skeletons of the victims of Genghis Khan, Captain Burslem and Lieutenant Sturt proceeded through several low arches and smaller caves, and reached at length a vast hall, in the centre of which was an enormous mass of clear ice, smooth and polished as a mirror, and in the form of a gigantic beehive, with its dome-shaped top just touching the long icicles which depended from the jagged surface of the rock. A small aperture led to the interior of this wonderful congelation, which was divided into several compartments of every fantastic shape. In some the glittering icicles hung like curtains from the roof; in others, the vault was smooth as glass. Beautifully brilliant were the prismatic colours reflected from the varied surface of the ice when the torches flashed suddenly upon them as they passed from cave to cave. Around, above, beneath, everything was of solid ice, and being unable to stand on account of its slippery nature, they slid, or rather glided mysteriously, along the glassy surface of this hall of spells. In one of the largest compartments the icicles had reached the floor, and gave the idea of pillars supporting the roof.’[27] Footnote 27: Burslem, ‘A Peep into Toorkistan.’ Rocks of volcanic formation seem to afford favourable opportunities for the congelation of water. Ice-caves are found in Mount Etna, on the Peak of Teneriffe, and among the lava-currents of Iceland.[28] Scrope visited one of these natural glacières near the village of Roth, in the neighbourhood of Andernach, on the Rhine. It formed the mouth of a deep fissure in a current of basalt derived from an ancient volcanic cone above it, and its floor was covered with a crust of ice at the time of his visit, about noon on a very hot day in August. Footnote 28: The Cave of Suitshellir. The phenomenon of wind-grottoes is analogous to that of ice-caves, and not seldom associated with it. Here cold currents of air, increasing in violence as the day is hotter, are found to blow from the interstices of rocks. One of the most celebrated of these Æolian caverns is found near Terni in Italy. The entrance is closed by an old gate, through the crevices of which the wind issues with a rustling noise, while in the grotto itself the current is sufficiently strong to extinguish a torch. The proprietors of some neighbouring villas have put the phenomenon to an ingenious use. Leaden pipes, branching out from the grotto, convey on sultry summer days an agreeable coolness through masks of gypsum with wide distended mouths, which are fixed in the walls of the apartments.