THE BASIN AND BED OF THE ATLANTIC. 321 



-c-ondiicts us into the very chambers of the deep. Our investiga- 

 tions go to show that the roaring waves and the mightiest billows 

 of the ocean repose, not upon hard or troubled beds, but upon 

 cushions of still water ; that everywhere at the bottom of the 

 ileep sea the solid ribs of the eaiih are protected, as with a 

 garment, from the abrading action of its currents, and that the 

 cradle of its restless waves is lined by a stratum of water at rest, 

 or so nearly at rest that it can neither wear nor move the lightest 

 bit of drift that once lodges there. 



506. TJie abrasion of currents. — The tooth of running water is 

 very sharp. See how the Hudson has gnawed through the 

 Highlands, and the Niagara cut its way through layer after layer 

 of the solid rock. But what are the Hudson and the Niagara, 

 with all the fresh water-courses of the world, by the side of the 

 Gulf Stream and other great " rivers in the ocean ?" And what 

 is the pressure of fresh water upon river-beds in comparison 

 with the pressure of ocean water upon the bottom of the deep 

 sea ? It is not so great by contrast as the gutters in the streets 

 are to the cataract. Then why have not the currents of the sea 

 worn its bottom away ? Simply because they are not permitted 

 to get down to it. Suppose the currents which we see at and 

 aiear the surface of the ocean were permitted to extend all the 

 way to the bottom in deep as well as shallow water, let us see 

 what the pressure and scouring force would be where the sea is 

 only 3000 fathoms deep — for in many places the depth is even 

 greater than that. It is equal there, in round numbers, to the 

 pressure of six hundi'ed atmospheres. Six hundred atmospheres, 

 piled up one above the other, would press upon every square 

 foot of solid matter beneath the pile with the weight of 1,296,000 

 pounds, or 648 tons. 



597. Their pressure on the bottom. — The better to comprehend 

 the amount of such a pressure, let us imagine a column of water 

 just one foot square, where the sea is 3000 fathoms deep, to bo 

 frozen from the top to the bottom, and that we could then, with 

 the aid of some mighty magician, haul this shaft of ice up, and 

 stand it on one end for inspection and examination. It would be 

 18,000 feet high ; the pressure on its pedestal would be more 

 than a million and a quarter of pounds ; and if placed on a ship of 

 <)48 tons burden, it would be heavy enough to sink her. There 

 are currents in the sea where it is 3000 fathoms deep, and sume 

 of them — as the Gulf Stream— run with a velocity of four miles 



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