32 IRISH LAKE-DWELLINGS, OR CRANNOGES. CHAP. n. 



natural position. The depth of overlying peat affords no safe 

 criterion for calculating the age of the cabin or village, for I 

 have shown in the ' Principles of Geology' (ch. xlvi.j, that both 

 in England and Ireland, within historical times, bogs have 

 burst and sent forth great volumes of black mud, which has 

 been known to creep over the country at a slow pace, flow 

 ing somewhat at the rate of ordinary lava-currents, and some 

 times overwhelming woods and cottages, and leaving a deposit 

 upon them of bog-earth fifteen feet thick. 



None of these Irish lake-dwellings were built, like those 

 of Helvetia, on platforms supported by piles deeply driven 

 into the mud. f The Crannoge system of Ireland seems,' 

 says Mr. Wylie, 'well nigh without a parallel in Swiss 

 waters.' 



