i 



CONTOUK OF OCEANIC BASINS. 



CHAPTER II. 



OCEANIC BASINS.-DEPTH OF THE SEAS.-LEVEL OF THE SUEPACE OF THE OCEAN. 



The seas which cover the greater part of this planetary sphere have 

 not completely enclosed basins. They all have their origin in the 

 great commoi reservoir of the Antarctic Ocean, and communicate 

 with each other by wide straits, or by sheets of water of secondary 

 importance. This partial absence of boundaries, and their enormous 

 extent of surface, deprive the seas of that harmony of form observable 

 in the continental masses. Yet, wherever the water washes the 

 shores of the land, it necessarily reproduces its contour ; and, in con- 

 sequence, the sea everywhere presents a distribution exactly the 

 opposite of that of the earth. The twofold basin of the Atlantic with 

 its wide central expansion, corresponds to the two continents of 

 America with their narrow uniting isthmus. The Pacific itself is 

 divided by its immense Archipelago into two vast distinct seas ; and 

 the Indian Ocean in the south balances the mass of Asia in the north. 

 Whilst limiting with its waves the shores of the land, the ocean 

 penetrates far into the interior, either by large rounded gulfs like 

 those of Guinea and Bengal, or by seas bordered with chains of 

 islands and islets, like the China Sea and that of the Antilles, or by 

 an intricate network of channels like those of Sunda, and the Polar 

 Archipelago of America. Certain seas also are almost completely 

 enclosed, and communicate with the remainder of the ocean only by 

 narrow outlets, as is the case with the Mediterranean and the Ped Sea. 

 The bottom of all these seas is not always horizontal or even regu- 

 larly inclined. It is certain that the bed of the sea has, like our con- 

 tinents, but in a far less degree, plateaux, valleys, and plains. Geology 

 reveals to us that in the course of ages the highlands of the con- 

 tinents sink beneath the oceanic expanses, and the abysses formerly 

 hidden by their waters emerge to the light and reveal the inequalities 

 of their surface. Were not the plains and the hills, which now bear 

 our cities and our harvests, in past ages covered by the waters of the 

 deep ? Do we not see on the flanks of the Himalayas, 18,000 feet above 

 the level of the mouth of the Ganges, shells which the sea has there 

 deposited in the strata ? And do not our navigators search the bottom 



