JlOir LAGOONS ARE FORMED 195 



branching in the manner of a river, which often extend many 

 miles beyond the entrance. The principal of these occupy a 

 position between the mouths of the main rivers which enter 

 the lagoon and the passage through the barrier reef, but others 

 lie parallel to the shore to the point where the tidal How, 

 which enters from a neighboring passage, produces a field of 

 waters in which there is practically no current. At these 

 nodal points or positions of no current the accumulation of 

 sand blowing across the island from the sea beach, together 

 with such vegetation as can inhabit the brackish water and by 

 its decay serve to fill the inlet, is likely to produce a low 

 barrier or isthmus uniting the neighboring islands and the 

 mainland. Such a barrier between adjacent inlets is commonly 

 known by the name of " haulover," a term derived from the 

 fact that small vessels are often dragged across it. 



Where the lagoon is narrow and shallow these isthmuses 

 or "haulovers" are likely to be developed between the prin- 

 cipal inlets. Where, however, the lagoon is large and fairly 

 deep, certain peculiar accidents are apt to keep united a great 

 stretch of the enclosed waters communicating with the sea by 

 several inlets. The formation of the isthmuses is mainl)- 

 prevented by the action of winds which occasionally produce 

 currents of sufficient strength in the relatively shallow water 

 of the lagoon to scour away the debris whenever it tends to 

 accumulate. Moreover, as will shortly be explained, these 

 inlets of the sand reef tend to become closed so that the Hoods 

 from a particular river are compelled from time to time to 

 make journeys in diverse directions in order to find an open 

 channel by which they may escape to the sea. Thus in the 

 long^est connected laeoon of the American coast — that on the 

 eastern shore of Florida known as the Indian River — each 



