xvi CONTENTS. 



ACTION OF RIVERS AND CURRENTS ON THE 150TT0M 

 OF THE SEA. 



1. Choking of ports with sand— Deltas, and the action of the 



tide upon them — The formation of deltas may be either 

 favoured or retarded by marine currents according to 

 circumstances — Deltas formed in shallow seas — Rapid 

 growth of the delta of the Po due to the clearing of the 

 south side of the Alps, and to the damming-in of the 

 shores of the river ....... 351 



2. Egypt, according to Herodotus, a present from the Nile . 357 



3. Description of the delta of the Mississippi — A village at 



anchor — Ships lost in the sand and mud of the river . 360 



4. Rapid growth of the deltas of the Po and of the Mississippi 



— ^Delta of the Nile enlarged by seven miles during the 

 historic period — The Rhone 36? 



5. Littoral accumulations — Coast-line — Marine lagoons and 



pools — Lagoons moved inland by the effects of the dunes 

 in Gascony — Villages buried beneath the dunes near 

 St. Pol-de-Leon in Brittany, and also in Gascony— 

 Bordeaux menaced . . . . . . .371 



6. Floating icebergs — Polar winters 37^' 



INFLUENCE OF LIFE ON VARIATIONS IN THE BED 

 OF THE OCEAN. 



1. Formation of coral reefs ; limit to their growth — Condi- 



tions favourable to their development .... 380 



2. Life and inanimate nature — Coral insects die in the calm 



of deep waters — Explanation of the formation of the deep 

 reefs of the Pacific Ocean— Coast reefs — Broken leeh — 

 Barrier reefs of Australia — How the coral reef becomes 

 an island 383 



3. Slowness of the growth of coral reefs — Florida Keys — De- 



struction of coral islands during a tempest in January 

 1865 — Regions in which coral reefs are found . . 390 



4. Algae — Submarine forests and prairies — Floating seaweed 



of the Sargossa seas — Extension of the coasts by the Rhi- 

 zophora Mangle 393 



INSIGNIFICANCE OF MAN COMPARED WITH THE OCEAN 396 



