THE BUILDING OF THE LAND 29 



ever, permit the migration across it of the highland 

 vegetation as the mainland just .back of it was a 

 great swamp. 



The dissolving of the soft limestone rock is 

 nowhere more evident than in the pine woods 

 bordering the Everglades. Before the recent 

 drainage of this region the glade lands were cov- 

 ered with fresh water throughout the rainy sea- 

 son, and sometimes during the entire year. Rain 

 water absorbs a considerable amount of carbonic 

 acid or carbon dioxide as it falls through the 

 atmosphere, and much more is added to it by 

 decomposing vegetation. This Everglade fresh 

 water often extends well out over the low pine 

 woods and has carved the rocky forest floor un- 

 til it is quite as rough and ragged as is that of 

 the keys. Hence the irregular sinks and many 

 potholes, and the uneven surface of villainous 

 knife-like edges which render walking over it 

 a really hazardous undertaking. In places the 

 honey-combed rock becomes so undermined and 

 rotten that it breaks under the tread, but woe 

 unto him who falls upon it ! 



So level is the general face of the country that 

 surface water sometimes seems undecided which 



