The astronomer takes exception to the term ’underground glacier’[120] which had been applied to this cavern.  He represents that the mountain is abundantly covered each winter with snow, in the neighbourhood of the ice-cave, which is nearly within the snow-line, and the stores of snow thus accumulated in the cave have no great difficulty in resisting the effects of summer heat, since all radiation is cut off by the roof of rocks.  The importance of this protection may be understood from the fact that in the middle of July the thermometer at this altitude gave 130 deg. in the sun, but fell to 47 deg. when relieved from the heat due to radiation.  At the time of this observation, there were still patches of snow lying on the mountain-side, exposed to the full power of direct radiation; and, therefore, there is not anything very surprising in the permanence of snow under such favourable circumstances as are developed in the cave.  Mr. Airy, a few summers ago, found the rooms of the Casa Inglese, on Mount Etna, half filled with snow, which had drifted in by an open door, and had been preserved from solar radiation by the thick roof.[121]

Humboldt remarks, that the mean temperature of the region in which the Cueva del Hielo (ice-cave) occurs, is not below 3 deg.  C. (37.4 deg.  F.), but so much snow and ice are stored up in the winter that the utmost efforts of the summer heat cannot melt it all.  He adds, that the existence of permanent snow in holes or caves must depend more upon the amount of winter snow, and the freedom from hot winds, than on the absolute elevation of the locality.

The natives of Teneriffe are men of faith.  They have large belief in the existence and intercommunication of numerous vast caverns in the Peak, one of which, on the north coast, is said to communicate with the ice-cavern, notwithstanding 8 miles of horizontal distance, and 11,000 feet of vertical depth.  The truth of this particular article of their creed has been recently tested by several worthy and reverend hidalgos, who drove a dog into the entrance of the cavern on the sea-coast, in the belief that he would eventually come to light again in the ice-cave:  he was accordingly found lying there some days after, greatly fatigued and emaciated, having in the interval accomplished the 11,000 feet of subterranean climbing.  How he could enter, from below, a water-logged cave, does not appear to have been explained.

FOOTNOTES: 

[Footnote 98:  The Caves of Szelicze are mentioned in Murray’s Handbook of Southern Germany (1858, p. 555), where the following account is given of them:—­’During the winter a great quantity of ice accumulates in these caves, which is not entirely melted before the commencement of the ensuing winter.  In the summer months they are consequently filled with vast masses of ice broken up into a thousand fantastic forms, and presenting by their lucidity a singular contrast to the sombre vaults and massive stalactites of the cavern.’