THEORY OF THE EARTH. 25 



Of Slips, or Falling down of the Materials of 

 Mountains. 



In every place where the broken strata present 

 their edges on abrupt surfaces, there fall down to 

 their base, every spring, and even after every 

 storm, fragments of their materials, which are 

 rounded by rolling upon each other. These col- 

 lected heaps gradually assume an inclination deter- 

 mined by the laws of cohesion, and thus form, at the 

 bottom of the cliff, taluses, of greater or less eleva- 

 tion, according as the fragments which have fal- 

 len are more or less abundant. These taluses 

 constitute the sides of the valleys in all elevated, 

 mountainous regions, and are covered with a rich 

 vegetation, whenever the fragments from the up- 

 per parts begin to fall less abundantly ; but their 

 want of solidity subjects themselves also to slips, 

 when they are undermined by rivulets. On 

 these occasions, towns, and rich and populous dis- 

 tricts, are sometimes buried under the ruins of a 

 mountain ; the courses of rivers are interrupted, 

 and lakes are formed in places which were be- 

 fore the abodes of fertility and cheerfulness. For- 

 tunately these great slips happen but seldom, and 



entitled " Geschechte der Natiirliche Veranderungen der 

 Erdoberflache," 2 vols. 8vo. Goth. 1822 and 1824. The facts 

 contained in it are collected with equal care and erudition. 



