DOMAIN XI. bECOMPOSEDv 



paration only of the integrant parts ; both 

 often take place in the same substance, 

 causes. " The only causes of mere disintegration 

 as yet known, are the vicissitudes of the 

 atmosphere ; the absorption and congela- 

 tion of water ; the sudden dilatation or 

 contraction produced by the former, par- 

 ticularly when extreme, cannot but loosen 

 the texture of most stony substances, and 

 when aided by the absorption of water, 

 strongly tend to separate them. The water 

 thus received in their minutest rifts, being 

 afterwards frozen, bursts them with incre- 

 dible force, of which frequent instances 

 occur in the northern countries, and in the 

 more elevated mountains of the southern, 

 where the most sudden transitions of heat 

 and cold, and the highest degrees of the 

 latter, frequently prevail; and hence the 

 broken craggy state of their loftiest sum- 

 mits*. 



" The known external causes of decom- 



* Crantz has informed us that, in Greenland, the rocks are often* 

 heard to burst with a noise like thunder. P. 



