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



natui'al position. The depth of overljang 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.), 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, 

 flowing somewhat at the rate of ordinary'' lava-currents, and 

 sometimes 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 supj^orted by piles deeply driven 

 into the mud. "The Crannoge system of Ireland seems/' 

 says Mr. Wylie, "welluigh without a parallel in Swiss 

 waters." 



