CURRENTS OF THE -SEA. 159 



founded upon the assumption that when water, in consequence of 

 its specific gravity, once sinks below the bottom of a current 

 where it is shallowest, there is no force of traction in fluids, nor 

 anj other power, which can draw this heavy water up again. If 

 such were the case, we could not have deep water immediately in- 

 side of the bars which obstruct the passage of the great rivers into 

 the sea. Thus the bar at the mouth of the Mississippi, with only 

 fifteen feet of water on it, is estimated to travel out to sea at rates 

 varying from one hundred to twenty yards a year. 



.434. In the place where that bar was when it was one thousand 

 yards nearer to New Orleans than it now is, whether it were fif- 

 teen years ago or a century ago, with only fifteen or sixteen feet 

 of water on it, we have now four or five times that depth. As 

 new bars were successively formed seaward from the old, what 

 dug up the sediment which formed the old, and lifted it up from 

 where specific gravity had placed it, and carried it out to sea over 

 a barrier not more than a few feet from the surface? Indeed, 

 Sir Charles himself makes this majestic stream to tear up its 

 own bottom to depths far below the top of the bar at its mouth. 

 He describes the Mississippi as a river having nearly a uniform 

 breadth to the distance of two thousand miles from the sea,* He 

 makes it cut a bed for itself out of the soil, which is heavier than 

 Admiral Smyth's deep sea water, to the depth of more than two 

 hundred feetf below the top of the bar which obstructs its en- 

 trance into the sea. Could not the same power which scoops out 

 this solid matter for the Mississippi, draw the brine up from the 

 pool in the Mediterranean, and pass it out across the barrier in 

 the Straits ? 



435. The traction of locomotives on rail-roads and the force of 

 that traction is well understood. Now have not currents in the 

 deep sea power, derived from some such force ? Suppose this un- 

 der current from the Mediterranean to extend one hundred and 

 sixty fathoms down, so as to chafe the barrier across the Straits. 



* " From near its mouth at the Bahze, a steam-boat may ascend for two thousand 

 miles with scarcely any perceptible diflference in the width of the river." — Lyell, p. 263. 



t " The Mississippi is continually shifting its course in the great alluvial plain, cut- 

 ting frequently to the depth of one hundred, and even sometimes to the depth of two 

 hundred and fifty feet." — Lxjdl, p. 273. 



