350 



FLOODS CAUSED BY LANDSLIPS. 



[Ch. XV. 



flood, and the whole mass of masonry disapi3eared in the bed 



of the river. 



Mr 



m ;y 



forced a mass ol lour or live hundred tons ot stones, many of 

 them two or three hundred pounds' weight, up an inclined 

 plane, rising six feet in eight or ten yards, and left them in 

 a rectangular heap, about three feet deep on a flat ground : 

 the heap ends abruptly at its lower extremity.'* 

 The power even of a 



sm 



removing: heavy bodies, was exem 



vity from 



>o-e, a small stream which flows at a sligh.1 

 the eastern water-shed of the Cheviot 



Hills. 



Several thousand 



tons' weight of 



gravel 



and sand were 



transported to the plain of the Till, and a bridge, then in 

 progress of building, was carried away, some of the arch- 

 stones of which, weighing from half to three quarters of a 

 ton each, were propelled two miles down the rivulet. On the 

 same occasion, the current tore away from the abutment of a 



mill 



a large block 



of greenstone-porphyry, weighing 

 nearly two tons, and transported it to the distance of a 

 quarter of a mile. Instances are related as occurring repeat- 

 edly, in which from one to three thousand tons of gravel are, 

 in like manner, removed by this streamlet to still greater 



distances in one day.f 



Floods caused by landslips, 1826. — The power which run- 

 ning water may exert, in the lapse of ages, in widening and 

 deepening a valley, does not so much depend on the volume 

 and velocity of the stream usually flowing in it, as on the 



number 



ma 



different periods, opposed its free passage. 



small 



If a torrent, 

 Le size of the 



temp 



and its declivity below, 



dimensions 



violence of the debacle. The most universal source of local 

 deluges are landslips, slides, or avalanches, as they are some- 



masses 



cases ice and snow, are precipitated into the bed of a river, 



* Quarterly Journ. of Sci., &c. No. 

 xiii. Now Series, p. 331. 



f Culley, Proceed. Geol. Soc. 1829. 





