GEOLOGICAL SOCIETY OF LONDON. 



147 



to be horizontally stratified, but this, Mr. Murchison says, 

 is owing to the mineral being excavated in large parallel- 

 lopipedal blocks, twelve feet long, three deep, and three wide, 

 which are separated vertically from the great body of salt by 

 grooves, with a hatchet, and then detached horizontally 

 by means of a heavy beam of wood suspended from triangles, 

 and driven against the face of the block. The upper surface 

 of the rock is irregular in outline, penetrating, in some places, 

 through the overlying sands and marls ; the base of the 

 exposed mass is worn on the side first excavated into a 

 cavern, by the action of dissolved snow and other causes, 

 the roof of the cavern being adorned by pendant saline 

 crystallizations. The entire range of this great deposit has 

 not been ascertained, but Mr. Murchison is of opinion that it 

 forms the subsoil of a considerable area. Its entire thickness 

 has also not been determined, but it greatly exceeds iOO 

 feet. In consequence of the salt occurring so near the sur- 

 face, every part supplied with springs from below is af- 

 fected by it. 



The freezing cave is situated on the base of a little hillock 

 of gypsum, at the eastern end of the village of Illetzkaya 

 Zatcheta, and is distinguished from other adjacent caves, 

 either natural or artificial, by abounding with ice in summer, 

 and containing no ice in winter. The roof is covered with 

 icicles, as well as the floor with snow and ice — all which dis- 

 appear in winter. This paper was concluded with various 

 conjectural reasonings respecting these phenomena; after 

 which those of Sir John Herschel were submitted, of which 

 we give the summary. After referring to some instances of 

 great cold in caverns or excavations during summer, Sir 

 John Herschel observes, it is clear that the cause cannot be 

 ascribed to the evaporation or condensation of vapour. The 

 temperature of Orenburg not being known to Sir John 

 Herschel, he is induced to reason from that of Ekaterin- 



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