"Yes," the other answered, "there have been many scores of lives lost
and many millions of dollars swept away on the 'Father of Waters,' and I
doubt if the time will ever come when the flood danger will be at an
end. Remember that the Mississippi River Valley is the only water outlet
for two-thirds of the entire United States."

"It's protected by levees, too, isn't it?" Colin queried. "At least,
during the flood on the Mississippi, you always hear of the levees
breaking or just going to break."

"They give way very seldom now," his chief replied, "and that means
wonderful engineering, for there are sixteen hundred miles of levee, the
river banks being built up clear from Illinois to the Gulf."

"Then where are the floods one hears of so often?"

"There are bad floods on the Ohio," was the reply, "and there is always
danger when a flood tide comes down the Mississippi. You see, if part of
a levee does give way, or as they say, if a 'crevasse' comes, thousands
of square miles are inundated, hundreds of people made homeless, and the
property loss is incalculable. All the land around the lower part of the
Mississippi is just a flood plain which used to be covered with water
every year. That land has been rescued from the river just as Holland
has been rescued from the sea."

"Then there is danger every year?"

"There is always danger," was the reply, "and the levees are carefully
patrolled. But during the high water of early summer there is more
danger, and a week's rain means trouble. We're going to have a bad flood
this year unless the rain stops soon."

"But the river isn't rising?"

"Not yet. Why should it? It isn't the water that flows directly into the
Mississippi, but that which floods the tributaries that causes disaster.
From the Rocky Mountains on the one side to the Alleghanies on the
other, and from the Gulf of Mexico to Canada--nearly every drop of rain
that isn't evaporated or used by plants has to be carried to the sea by
the Mississippi."

"It seems like a big job for one river bed," Colin agreed. "But how can
it be made safer?"

"The way is easy," was the answer, "but costly. If big reservoirs are
built on all the headwater streams so that--no matter what the rainfall
may be--only a constant amount is allowed to flow out of these
reservoirs, then floods will be avoided, there will be plenty of water
for irrigation, and a steady depth of water in the channel will extend
navigation that is now s