198 FROZEN WELL. 



following he again visited this well ; the water had fallen somewhat, but a mass of ice as 

 large as a wash tub was still floating in it." 



The cases which follow, although different in some respects from those above described, 

 appear to belong to the same class of phenomena, and may furnish some hints towards 

 a solution of the problem before us. 



The 45th volume of the American Journal of Science, p. 78, contains an account of "Ice 

 Mountain" in Virginia, by C. B. Hay den, where an enormous mass of debris rises 

 several hundred feet against a rocky wall, and spreads as far horizontally ; the fragments 

 varying in size from a few inches to many feet in diameter. The interstices are occupied 

 by ice, which remains, even only a few inches from the surface, through the summer. 



Mr. Hayden explains this case on the principles of the common refrigerator, the debris 

 forming the non-conducting sides. " The Ice Mountain, he says," is in fact a huge sand- 

 stone refrigerator, whose increased and unusual effects beyond those of the ordinary 

 refrigerator, are due to the increased and unusual collection of poor conducting materials, 

 which form its sides." 



In the 46th volume of the same Journal, p. 331, Dr. S. Pearl Lathrop has described a 

 similar Ice Mountain in Wallingford, Vt., where a mural front of quartz rock has a tal us 

 of loose fragments covering an area at the base from 30 to 50 acres ; and in a ravine open- 

 ing to the southwest, where the fragments have been thrown, the ice occurs. It disappears 

 from about first of July to September. Some of us have visited this spot, and presume 

 Dr. Lathrop to be correct in accounting for the preservation of the ice on the theory sug- 

 gested by Mr. Hayden; though, as we shall state further on, we should modify his theory 

 considerably. 



The "Ice Caverns" that have been described in Europe and Asia, present another phase 

 of this subject deserving attention. Some of them were described long ago by Saussure 

 and Pallas. In 1823 Prof. Pictet, of Geneva, presented in the Edinburgh Philosoph- 

 ical Journal (Vol. VIII, p. 1,) full details of the most interesting cases that occur in the 

 Alps and the Jura. Two are noticed in each of these mountains. They are essentially 

 alike, consisting of grottoes or caverns, one of which had on its bottom a surface of 3000 

 square feet of ice a foot thick, which was quarried in summer and constantly renewed. 

 From most of them there issued a strong current of cold air. This current was more 

 powerful, and the refrigeration most active, in the hottest summers. Water was found in 

 them all, and the air was quite damp and filled with vapor. Another cavern called " The 

 Natural Glacier of the Rothorn in the Alps," is described by M. Dufour, in the same 

 volume of the Ed. Philos. Journal, p. 290. 



These caverns were so situated that snow could not have entered them to much extent 

 during the winter. Prof. Pictet, as did Saussure before him, explains the refrigeration by 

 supposing currents of air descending into the caverns in summer and escaping from the 

 grottoes at the bottom. This current acquires in its descent the temperature of the sur- 

 rounding rock, and is also greatly cooled if moisture cover the stones, by its evaporation. 

 In winter the current of air is reversed, ascending through the uppermost opening. Then 

 the evaporation is less-than in summer, and consequently the cold produced is less. 



To sustain these views, Prof. Pictet quotes many other facts. In Rome is a hill 200 to 

 300 feet high, called Monte Testaceo, composed almost wholly of broken urns and other 



