[4]
[Footnote 4: "The bed of the river is so broad that the channel
meanders from side to side within the bed, just as the bed itself
meanders from bluff to bluff; and, as by erosions and deposits, the
river, in long periods of time, traverses the valley, so the channel
traverses the bed from bank to bank, justifying the remark often
heard, that 'not a square rod of the bed could be pointed out that had
not, at some time, been covered by the track of steamboats.'"--J.H.
SIMPSON, _Col. Eng., Brevet Brig.-Gen., U.S.A._]
PHYSICAL.
The lower Mississippi is among the muddiest streams in the world.
During the average year it brings down 7,500,000,000 cubic yards of
sediment, discharging it along the lower course, or pushing it into
the Gulf. As one thinks of the small amount of sediment held in a
gallon or two of river water, a comprehension of this vast amount of
silt is impossible. It is enough to cover a square mile in area to a
depth of 268 feet. In five hundred years it would build above the sea
level a State as large and as high as Rhode Island. Thus, by means of
this sediment, the river has pushed its mouths fifty miles into the
sea, confining its flow within narrow strips of land--natural levees
made by the river itself.
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