THE FORMATION AND PRESERVATION 

 OF HARBORS 



Lagoon Harbors; their Origin and History. — Effect of Wind-hlown Sands. — SandSiiit 

 Harbors. — Effect of Water-borne Sands. — Crater Harbors. — Coral-Reef Harbors ; 

 Division into Two Classes ; Ways in which constructed. — Preservation and Destruction 

 of Harbors ; Ways in which they act ; Tidal Action ; Changes of Level ; Accumula- 

 tion of Sediments ; Invasion of Marine Waste. — Relative Importance of Damaging 

 Agencies in Lake and Sea Harbors. — Effect of Pocket-Beaches. 



Wherever the water next a shore is shallow and the 

 bottom sandy and the waves have considerable strength, we 

 find a series of elongate low-lying islands which more or less 

 completely enclose a shallow field of waters commonly termed 

 a lagoon. Although sand-bar islands of this description fre- 

 (jucntly occur along the shores of other continents, they are 

 perhaps most characteristically exhibited on the eastern coast 

 of North America. T^rom the high nortli southward along 

 the shore to Portland, Maine, the water is so deep and the 

 bottom so free from sand that the waves moving toward 

 the shore do not obtain possession of sufficient detritus to 

 form extensive barriers of this description. South of Port- 

 land and thence to Cape bdorida these sand reefs are so 

 generally developed that they form a tolcrabl)- connected 

 barrier between the mainland and the open sea. From the 

 waters of Chesapeake Pay to tliose of Biscayne Bay, a dis- 

 tance of about seven hundred miles, this natural rampart 

 of sand is so continuous and the hiLroons which it shelters so 



