X CONTENTS 



HARBORS AND CIVILIZATION 



PACK 



First Condition of Ships. — Oii(;in of Maritime Habit ; Relation of Habit to Form of 

 Shore ; Effect on National Progress. — Condition of North America as regards 

 Harbors. — Requirements of a Good Port. — Classiiication of Harbors. — Delta Har- 

 bors. — Valley Harbors : How Dependent on Changes of Level. — Fiord Harbors : 

 The Conditions of their Formation; Value as Ports. — Mountain Range Harbors. — 

 Morninal Harbors I53 



THE FORMATION AND PRESERVATION OF HARBORS 



Lao-oon Harbors ; their Origin and History. — Effect of Wind-blown Sands. — Sand-Spit 

 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 ; Accumulation of Sediments ; Invasion of Marine Waste. — Relative Im- 

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

 Beaches ^^7 



TIDAL CURRENTS AND ORGANIC LIFE IN HARBORS 



Effects of Tides on Harbors : Organization of Tidal Streams ; Effect of Tidal Bars. — 

 Action of Organic Life in Harbors ; Classes of Work done.— Effect of Marine 

 Plants ; Flowering Species ; Sea-Weeds. — Growth of Marine Marshes : their Rela- 

 tion to Tidal Currents; their Value for Tillage, — Tropical Marine Marshes. — 

 Effect of Mangroves on these Areas. — Effects of Organic Life,xm FJarbor-s : Work 

 done by Mollusks ; by the Common Oyster ; Comparison of Northern and Southern 

 Marine Marshes ; Work done by other Animal Species. — Synopsis 223 



