THE LEVELLING POWER OF RAIN. 375 



Besides slow landslips, however, rain not unfrequently 

 causes great masses of earth to be precipitated suddenly, 

 and where such masses fall into the bed of a river, local 

 deluges of great extent and of the most destructive character 

 often follow. The following instances, cited in an abridged 

 form from the pages of Lyell's " Principles of Geology," attest 

 the terrible nature of catastrophes such as these. 



Two dry seasons in the White Mountains of New Hamp- 

 shire were followed by heavy rains on August 28, 1826. 

 From the steep and lofty slopes of the River Saco great 

 masses of rock and stone were detached, and descending 

 carried along with them " in one promiscuous and frightful 

 ruin, forests, shrubs, and the earth which sustained them." 

 "Although there are numerous indications on the steep 

 sides of these hills of former slides of the same kind, yet no 

 tradition had been handed down of any similar catastrophe 

 within the memory of man, and the growth of the forest on 

 the very spots now devastated clearly showed that for a 

 long interval nothing similar had occurred. One of these 

 moving masses was afterwards found to have slid three 

 miles, with an average breadth of a quarter of a mile." At 

 the base of the vast chasms formed by these natural excava- 

 tions, a confused mass of ruins was seen, consisting of trans- 

 ported earth, gravel, rocks, and trees. Forests were prostrated 

 with as much ease as if they had been mere fields of grain ; 

 if they resisted for a while, " the torrent of mud and rock 

 accumulated behind till it gathered sufficient force to burst 

 the temporary barrier." " The valleys of the Amonoosuck 

 and Saco presented, for many miles, an uninterrupted scene 

 of desolation, all the bridges being carried away, as well 

 as those over the tributary streams. In some places 

 the road was excavated to the depth of from fifteen to 

 twenty feet ; in others it was covered with earth, rocks, and 

 trees to as great a height The water flowed for many weeks 

 after the flood, as densely charged with earth as it could be 

 without being changed into mud, and marks were seen in 

 various localities of its having risen on either side of the 



