Sir R. Murchison wrote to Russia for further information with respect to this cave in January 1865, and again in the beginning of April, addressing his second enquiry to the Secretary of the Imperial Academy.  In reply, the Secretary says that he is not aware that any thermometric observations have been made in the cavern.  He encloses a short statement by M. Helmersen, one of the members of the Academy, to the following effect:—­About 50 versts SE. of Miask, in the chain of the Ural, is a copper mine, called Kirobinskoy, which was abandoned more than fifty years ago.  On the 7th July, 1826, M. Helmersen found a thick wainscoting of ice on the sides and roof and floor of the horizontal gallery, within 10 feet of the entrance.  He was assured that this ice never melts, and that its thickness is greater in summer than in winter.  M. Helmersen adds, that to the best of his belief no one has investigated the cavern of Illetzkaya Zastchita since Sir R. Murchison’s visit.

The Ice-Cavern of the Peak of Teneriffe.[118]

This cave is at a height of 11,040 feet above the sea, and is therefore not far below the snow-line of the latitudes of the Canary Isles.  The entrance is by a hole 3 or 4 feet square, in the roof of the cave, which may be about 20 feet from the floor.  The peasants who convey snow and ice from the cave to the lower regions, enter by means of knotted ropes; but Professor Smyth had caused his ship’s carpenter to prepare a stout ladder, by which photographic instruments and a lady were taken down.

On alighting on a heap of stones at the bottom, the party found themselves surrounded by a sloping wall of snow, 3 feet high, and 7 or 8 feet broad, the basin in which they stood being formed in the snow by the vertical rays of the sun, and by the dropping of water from the edges of the hole[119].  Beyond this ring-fence, large surfaces of water stretched away into the farther recesses of the cave, resting on a layer of ice, which appeared to be generally about 2 feet thick.  At one of the deeper ends of the cave, water dropped continually from the crevices of the roof; a fact which Professor Smyth attributed to the slow advance of the summer wave of heat through the superincumbent rock, which was only now reaching the inner recesses of the loose lava, and liquefying the results of the past winter.  There would seem to be immense infiltration of meteoric water on the Peak; for, notwithstanding the great depth of rain which falls annually in a liquid or congealed form, the sides of the mountain are not scored with the lines of water-torrents.

Though occurring in lava, this cavern is quite different from lava-tunnels, such as the Surtshellir, which are recognised formations, produced by the cooling of the terminal surface-crust of the stream of lava, and the subsequent bursting forth of the molten stream within.  This, on the contrary, proved to be a smooth dome-shaped cave, running off into three contracting lobes or tunnels which might be respectively 70, 50, and 40 feet long, and were all filled to a certain depth with water:  in the smoothness of the interior surfaces, Professor Smyth believed that he detected the action of highly elastic gases on a plastic material.