ON THE DESTRUCTION OF ROCKS. 251 



in 1806, and the fall was so sudden as to overwhelm 

 nine out of thirteen persons who were travelling near 

 it at the time. This fall took place in the Rosenberg; 

 detaching the summit called the Knippenhoul, to- 

 gether with a portion of the adjoining ground. Falling 

 into the valley which separates the Lake of Zug from 

 that of Lawertz, and into the latter lake, it produced 

 an inundation which caused a great destruction among 

 the houses and the population ; obliterating at the 

 same time a large portion of the lake- The plain is 

 now covered by a hill, a hundred feet in height, and a 

 league and half in length and breadth. In this case 

 also, the cause was of the same nature, originating in 

 a lake situated above Spietsfleu- 



It is unnecessary to describe the minor events of the 

 same nature which have occurred in our own country, 

 as the causes have not always been so well ascertained. 

 But it ought to be added, that, in the Alps, great 

 devastation is sometimes produced by the sudden 

 eruption of lakes, caused by the wasting and bursting of 

 their barriers ; instances of which have been noticed 

 by De Luc and by Saussure. 



In terminating this subject, it must now be re- 

 marked, that the progress of disintegration and de- 

 composition is resisted by vegetation, and by the 

 accumulation of alluvial soil ; as it further is, in the 

 lower lands, by the diminution of the power of 

 gravity, and by the gradually diminishing ratio of the 

 other active powers of destruction. Thus it has been 

 remarked by Dolomieu, that, in the Lipari isles, the 

 volcanic fragments are first arrested by the vegetation 

 of shrubby plants, until, finally consolidated by a 

 more minute vegetation, they become a firm and 

 permanent covering to the mountains. In a similar 

 manner, in Sky, the dense coat of peat, impermeable 



