Mosses and Lichens 



itself becomes calcified and elevated, and, in the course of time, 

 banks of calcareous tufa are formed, which may attain to consider- 

 able dimensions. Banks raised in this manner are known which 

 are not less than forty-eight feet in height. To construct them, 

 it is estimated that mosses must have been at work on them for 

 more than 2,000 years. 



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