and on a remarkable Freezing Cavern. 13 



is, he observes, a very marked difference between the climate 

 of the steppes south of Orenburg and that of Ekaterinburg, 

 not merely due to the difference of six degrees of latitude, but 

 arising also from the altitude of the position of Ekaterinburg, 

 and the shortness of its varying summers, as well as from the 

 long droughty summers of the steppes, w'hich are removed 

 from all mountain chains, and possess comparatively no great 

 altitude above the sea. In the southern region, he conceives, 

 a substratum of frozen matter cannot exist, there being a most 

 extraordinary difference between the climate of Yakatsk (lat. 

 62i° N. long 131° E.), and that of Orenburg (lat. 51° 46' N.), 

 the winter of the former lasting eight or nine months, with 

 the thermometer during long periods constantly 30^, and some- 

 times 40° of Reaumur below zero.* 



Respecting the explanation that the difference of tempera- 

 ture in the cave is due to the propagation through the gypsum 

 hillock of the heat or cold of the preceding summer or win- 

 ter season, Mr Murchison conceives that the fissures which 

 ramify from the cave into the hill, present difiiculties to such 

 a solution. When he was on the spot, the existence of these 

 fissures led him to speculate upon the possibility of the phaeno- 

 mena being due to currents of air passing over subterranean 

 floors of moistened rock-salt, and on the effects which would 

 be produced when such currents came in contact with a stream 

 of drv heated air. 



* Mr Murcliison ascertained, during his journey in the North of Russia 

 in 1840, that much remains to be done relative to the circumstances of the 

 recorded frozen substratum of Yakatsk; and he states the following as 

 points requiring attention. \st. With the exception of about sixty feet of 

 alluvial soil, the whole shaft to a depth of .350 feet, was sunk through solid 

 strata of limestone two to six feet thick, and shale with a little coal ; 2dly, 

 That none of the sinkings took place in summer, although renewed for 

 several years, on account of the foul air generated in the shaft ; 3t%, That 

 when Admiral Wrangel descended the shaft during summer, and the sur- 

 face was burnt up, he found the thermometer to stand at 6° Eeaum. below 

 zero. 



