20 THE OCEAN. 



less arises from the alluvium brought down by the rivers and the 

 accumulations of organic remains. Thus the part of the globe covered 

 by the seas might be considered as perfectly round, and Newton's 

 hypothesis, explaining the bulging at the equator by the state of 

 fluidity m which the planetary mass had originally been, would 

 become unnecessary.* 



As to the mean depth of the whole mass of the marine waters, we 

 can hardly estimate it at less than about 3 miles; since, as we 

 have already seen, the entire basin of the Atlantic, and that of 

 the Northern Pacific, which border upon the great northern con- 

 tinents, are deeper by many hundreds or even thousands of fathoms. 



...^.^ ""^ ^^'^ ^''^''^ ^'"'^^'''^^ ^^ ^^^ occ^n, an extent of more than 

 14o millions of square miles, we find that the sea forms a volume of 

 about 2i million billions of cubic yards, that is to say, the 560th part 

 of the planet itself Sir John Herschel f gives much higher figures 

 lor the same volume of water; but he has taken, as the basis of his 

 calculation, the probable maximum of the depth of the seas, that is to 

 say lour English miles, more than 3,738 fathoms. We cannot speak yet 

 with certainty, but one day, thanks to the new observations which kre 

 added every year to those which science already possesses, it will be 

 possible to give figures more relatively exact for the depth of the 

 marine abysses, and the mass of water that fills them. One thing is 

 certain ; that the highest part of the continent raised above the sur- 

 lace ol the waters is of much less elevation than the depth of the 

 sea ; and we can estimate the land above the level of the sea at only 

 about a fortieth part of the mass of waters. Besides which, the 

 land Itself contains within it an enormous quantity of water united 

 either chemically or mechanically with all rocks. 



The water of the seas urged by the force of gravitation constantly 

 seeks Its level, like the water of rivers and lakes. When, in conse- 

 quence ot very rapid evaporation, or of a succession of tempests 

 blowmg from the same quarter of the horizon, the surface of the sea 

 IS lowered m any gulf, the waters from the adjacent parts rush 

 towards the impoverished space, to fill the void. In the same 

 way when great rains, the swelling of large rivers, or the action of 

 winds have raised the level of the sea in one point, this local swellino. 

 soon subsides, and its superfluity is dispersed over the surrounding 

 urfaces. ^ AVe may, therefore, consider the mean height of the sea as 

 tne same m every ocean, since the natural movement of water tends 



• Gesfalt der Erde und d.r Meere.Jlach,. t Physical Geography, p. 17. 



