Hot and Thermal Springs. 377 



valley ; into these the waters enter in the following spring, soften 

 the rocks, and thus cause their fall.* 



The alternation of frost and thaw also causes the dislocation, 

 and breaking done of considerable masses of rock. Thus 

 Gerard observed in the Himalaya mountains, that masses of an 

 enormous size were continually falling down from some rocks, 

 between which there were passes, at a height of 15,000 to 16,000 

 feet. The bottom of the passes was covered with immense 

 heaps of such fragments.-)- 



But the universal consequence of such fallings in of the rocks 

 will be, that the glaciers will lose their supply of snow, and will 

 decrease, or perhaps entirely disappear. Thus by degrees many 

 spots are reclaimed from the regions of perennial snow, and be- 

 come capable of sustaining organic life. 



Chap. X. — The frozen soil of northern Siberia is no contradiction to 

 the increase of temperature towards the interior of the earth. 



The whole of northern Siberia presents the singular phe- 

 nomenon, that, even in the hottest season, the soil remains fro- 

 zen from a certain depth downwards, differing according to 

 the latitude, and other local circumstances, and that the thick- 

 ness of this frozen stratum is so considerable in the more east- 

 erly places, as, for instance, at JaJcutzk, that its bottom has not 

 yet been reached J Gmelin relates that in the archives at Jo- 

 Jciitzk, he found an account of an inhabitant of that town hav- 

 ing, at the beginning of the last century, together with some 

 Jakuters, contracted to sink a well, and that when they had 



• We have proofs of the decrease of the height of the Alps in former times, 

 in the loose blocks of rock which lie scattered about in all directions, as it 

 seems certain, from the observations hitherto made, that they have been pre- 

 cii)ilated from the upper Alps. Die Umwalzungen derErdrinde von Cuvier, 

 translated by Noggerath, 1830. ii. j). 15. It is also proved by the deposits 

 from the alpine streams in places where their course is less rapid, by which 

 means enormous masses have been and still continue to be carried out of the 

 the Alps. 



+ N. Gcogrriph. Ephenieriden. xiv. p. 202 and 27G. 



+ To this phenomenon is to be ascribed the existence and the good pre- 

 servation of the great tropical animals, covered with their flesh and other soft 

 parts, found at the hiovith of ihe Lena, and on tiie t).inks of the IVUhui in la- 

 titudes 72° and i'li". 



