THALASSA. 



CHAPTER I. 



DEPTH OF THE OCEAN. 



Distribution of Land and Water — Depth of the Ocean — Configuration of the Sea- 

 bottom — Description of the Basin of the Atlantic — The Indian Ocean — The 

 Pacific — The Southern Ocean — The Arctic Sea — The Antarctic Sea. 



Distribution of Land and Water. — Our conception oi 

 the relative distribution of land and water over the surface of 

 the Earth has been hitherto limited to a comparison of the 

 superficial areas occupied by these two elements, such as they 

 are presented to us on a chart of the world. In this sense we 

 speak of the different continents and islands which constitute 

 the sum total of dry land, and of the different oceans and seas 

 which compose the water-surface of our planet. But if we 

 wish to form a more perfect idea of the distribution of land and 

 water, we must consider not only the length and breadth of the 

 areas occupied, but also the height of the land and the depth 

 of the water ; in other words, the volume of those portions of 

 the solid crust of the earth which are raised above the level 

 of the sea, and the volume of the masses of water which fill 

 up the depressed portions of the earth's crust. We are thus 

 led to regard the surface of the solid crust of our planet as 

 composed of heights and hollows, of areas of elevation and 

 areas of depression, and, as a next step, to discriminate between 

 these areas — not according to the usual standard of the level 

 of the sea, but according to their relative distance from the 

 centre of the earth. In this sense we may conceive an area of 



