24 IN LOWER FLORIDA WILDS 



begun the ridge acts as an obstruction to the in- 

 coming and outgoing tides, and more and more 

 material is deposited on and against it from both 

 within and without. Finally the ridge builds up 

 to the level of high tide and a bay or so-called 

 "river" is a result. More sand is heaped against 

 the outside of the ridge during very high tides or 

 incoming storms until eventually it becomes a long 

 island or peninsula, sometimes ten feet or more in 

 height. The wind may sweep the sand into dunes; 

 seeds and the flotsam of the sea are cast upon it 

 and the island is covered with a mantle of vege- 

 tation. Such a tidal peninsula has been formed 

 between New River Inlet (near Fort Lauderdale) 

 and Cape Florida, and the upper end of Biscayne 

 Bay is the resulting "river" that lies behind it. 

 Beginning at Snake Creek at the upper end of the 

 bay and extending for some distance to the north- 

 ward the space back of the tidal land has be- 

 come filled with vegetable muck until it is now 

 a swamp. There are generally open channels 

 at intervals between the bays or "rivers" and 

 the open sea, through which the tides rush 

 swiftly. 



Where the sea bottom slopes away very grad- 



