ty
years' time there would be land there for a farm."

"But a thousand tons a minute!" the boy repeated, "that seems huge!"

"It is pretty big," the Forecaster agreed, "but I'll show you where it
comes from. You know, boys, generally the land slopes down in the
direction of the river, doesn't it?"

"Yes," assented the two boys, "it's supposed to. But it doesn't here.
The lie of the land is away from the river."

"That's just exactly the point," the Forecaster declared. "The banks of
the Mississippi range in height from about twenty to forty feet above
extreme low water. As the river, in times of flood, rises as high as
forty to fifty feet above low water, unless there were levees, the river
would overflow its banks every spring or flood time."

"It does, quite often, even yet," commented Ross, looking on the flooded
scene around him.

"Well," said the Weather Man, "the present levee system only dates
back to the end of the Civil War, although there were levees built
during the first settlement of New Orleans, two centuries ago. Remember,
though, that the Mississippi has been flowing down its present bed for
several hundred thousand years, with a flood every spring, so that the
overflow has had its effect. Of course, before the land was broken up by
farming, there wasn't as much earth carried down into the river to make
mud as there is now.

"When the Mississippi River, with its heavy sediment, overflows the
banks into the swamps, it's easy to see that the current will be slower
in the flooded area than in the main bed of the river."

"Of course," agreed Ross, "but what has that got to do with it?"

"A great deal," the Forecaster replied succinctly. "The faster a river
flows, the more sediment it can carry without allowing it to drop to the
bottom; the slower it flows, the more readily is the sediment dropped.
If you put some mud in a glass of water and keep stirring it with a
spoon, the mud will never sink to the bottom. Even if you let it stand
perfectly still, it will take several days before the finest particles
sink to the bottom of the glass and the water becomes clear."

"Yes," agreed Anton, "I've often wondered why."

"Well," the Weather Man continued, "if you look closely at the mud in
the bottom of the glass, you'll see that the bigger particles are at the
bottom and then those a little smaller and so on up, until your top
layer is made of a mud composed of particles so fine that you'd have to
get