CATARACTS, AND INUNDATIONS. 283 



lebrated Dr. George Berkeley, Lord Bishop of Cloyne, who in the 

 course of his theory to account for the petrifying property of the 

 lake, gives us his opinion that stones are unorganized vegetables, 

 formed by an accretion of salts ; wl\ich he urges in opposition to 

 those of his own age, who conceived stones to be organized vege- 

 tables produced from seeds. Waters impregnated with calcareous 

 earth, and otiier petrifying materials, and productive of all the effects 

 here spoken of with astonishment, are now known to be frequent 

 in most parts of the world : one of the most curious examples, in 

 point of picturesque scenery, is perhaps theDropping-vvell at Knares. 

 borough; and we have already noticed -a similar property in several 

 other waters, especially in the lake of Solfatara in Campagna. 



[EDITOR.] 



SECTION XI. 



Inundations. 



WE have already observed that many of the large rivers of the 

 east, as the Nile, the Ganges, and the Indus, are subject to peri- 

 odical exundations, and have pointed out some of the more ob- 

 vious causes of such an effect. There are others, however, that 

 are subject to occasional overflows, and in many instances from 

 causes that are altogether concealed. Among these we may per- 

 haps enumerate the inundation of the Thames, about the year 

 1705, at Dagenham and Havering marches in Essex, which made 

 an excavation nearly twenty feet deep, and laid open a great num. 

 ber of trees, mostly alder, buried under a soil obviously composed 

 of the mud of the Thames, and which had, in all probability, been 

 overthrown by some previous inundation of a similar kind. 



The following, in the island of Mauritius, is to the same effect: On 

 the 22d of March, 1696, observes Mr. Witsen, at half an hour after 

 twelve o'clock, being calm but a little rainy, the river which passes by 

 the plain ground of Noardwyek, in the space of a quarter of an hour 

 swelled to such- a height, tiiat the sugar-mill, the sugar.work, and al- 

 most all the said ground was ruined,the most part of the sugar-canes 

 being rooted or torn out of the ground by the violence of the tor- 

 rent. It cannot be imagined what had caused so sudden a swelling 

 of this river, for the rain was not very hard, and could not have 

 produced that effect; for about twelve o'clock, when the coin- 



