382 THE PHYSICAL GEOGRAPHY OF THE SEA. 



In repeating tliese facts here, and the results derived therefrom, 

 let us, in the first j)lace, confine our attention to " blue water." It 

 is an established fact that there is no running water at the bottom 

 of the deep sea. The agents which disturb the equilibrium of the 

 sea, giving violence to its waves and force to its currents, all re- 

 side near or above its surface ; none of them have their home in 

 its depths. These agents are its inhabitants, the moon, the winds, 

 evaporation and precipitation, with changes of temperature — such 

 as heating here, and cooling there. 



The rays of the sun can not penetrate into the depths of the 

 ocean, and radiation can not take place thence ; consequently, the 

 change of the temperature in the depths of the sea, from summer 

 to winter, and from winter to summer, mnst be almost, if not en- 

 tirely, unappreciable. This is a generally admitted fact. 



The winds take up water from the surface, and not from the 

 depths, and in so doing they disturb the equilibrium of the water 

 at the top, not the equilibrium of the water at the bottom ; by 

 evaporation, the water on top becomes Salter and heavier than it 

 was before ; the vapor thus taken up is condensed into rain and 

 precipitated on other parts of the sea, thus both raising the sea- 

 level, and making the surface water lighter and less salt than it was 

 before. Thus we have the genesis of horizontal circulation, or an 

 interchange of water called currents. If, by the process of evap- 

 oration, the surface water becomes so salt as to be heavier than the 

 water at the bottom, the water at the bottom and the water at the 

 top will change places. This may give rise to a vertical circula- 

 tion, but one so feeble that it can not be felt by even the tiny little 

 shells which strew the bed of the ocean, and which lie there as 

 lightly as gossamer under the dew of the morning ; practically, 

 therefore, the water at the bottom is still. 



It is also generally admitted that the waves, even in their most 

 angry moods, are incapable of reaching far down in the sea, or of 

 disturbing the quiet and repose which reign in its depths. 



In short, there is reason to believe that the bottom of the deep 

 sea is every where protected from the violence of its waves, the 

 abrading action of its currents, and the rage of the forces which 

 are ever at play on its surface, by a cushion of still water. 



The grounds for this belief are contained in these pages, but, to 

 recapitulate briefly, they are afforded by these circumstances: 



