430 



that it requires six mouths for the wave of cold, as he terms it, to 

 reach the cavern, and consequently, that that frigid wave begins to 

 arrive at the commencement of summer, and continues during that 

 season, occasioning such a degree of cold in the cavern as to pro- 

 duce the congelations described by Mr Murchison. 



At the commencement of winter, the first effect of the summer's 

 heat arrives, and continues without interruption, and occasions 

 warmth enough to prevent congelation. 



Dr Hope entirely concurred with Sir John Herschel in thinking 

 that alternate waves of heat and cold must exist and have a share 

 in producing the phenomena, and in corroboration quoted the ob- 

 servations of Saussure, that at Geneva the winter's cold requires 

 six months to descend 29 i^ feet, and that the summer's heat 

 penetrates to the same depth in a similar period of time ; the 

 maximum of cold taking place at mid-summer, and of heat at mid- 

 winter. 



But he also expressed his conviction that these alternate waves were 

 not sufficient to account for the phenomena, further I'emarking, that 

 were they the only powers employed, the paradoxical phenomena 

 should occur equally in some of the other caverns of the Orenburg 

 hillock, or in other caverns in different quarters of the globe. He 

 observed, that there must be something peculiar to the lUetykaya 

 Zatchita cavern which renders it the only cave in the world which 

 possesses the singular property, so far as he knew. He then al- 

 luded to the caverns in different parts of the globe in which ac- 

 cumulations of snow are found in summer, and concurred with Mr 

 Murchison in thinking that they have no analogy with that of Oren- 

 burg. They are merely receptacles of the winter snow and ice, and 

 preserve it during summer, after the manner of an ice-house. 



The circumstance peculiar to the Orenburg cave is the occur- 

 rence of the rents and fissures which rise from the back part of 

 the cavern. 



The author stated, that if it were granted that these fissures reach 

 the surface, even by the smallest ramifications, and that they ascend 

 within the reach of the alternate waves of heat and cold, the whole 

 phenomena may be easily and satisfactorily explained. He ascribed 

 the summer's coldness and congelation to a constant curi'ent of cold 

 air through the fissures of the rock into the cavern ; and he sup- 

 posed that the current is occasioned in the following manner : When 



