“How did it come to do that?” asked Will. “Why didn’t it find its level as water generally does--” “And as men ought to do, but usually don’t,” said Irv. “It did at first, of course,” said Ed. “But whenever it got on a rampage like this, it took all the region along its course for its right of way. It spread itself out over the country and went whithersoever it chose. Then came men who wanted its rich bottom lands for farms. So they built earth levees to keep the river off their lands. As more and more lands were brought under cultivation, more and more of these embankments were built, and the river was more and more restrained. Now there is nothing in the world that resists and resents restraint more than water does. So the river breaks through the levees every now and then and floods the plantations, drowning cattle, sweeping away crops and houses, and creating local famines that must be relieved from the outside.” Before beginning his explanation Ed had dipped up a glassful of the river water and set it on the deck. It was thick with mud, so that it looked more like water from a hog wallow than water from a river. He turned now and gently took up the glass. There was a deep sediment in the bottom and the water above was beginning to grow somewhat clearer. “Look here,” said the boy. “If we let that water sit still long enough, all the mud would sink to the bottom and the water above would become clear. That’s what we should have to do with our drinking and cooking water on this boat if we hadn’t brought a filter along. Now you see that the water of this river is carrying more mud than it can keep dissolved. This mud is sinking to the bottom all the way from St. Louis to New Orleans. It is building up the bottom, raising it year by year, and so raising the river higher and higher. When the river was left free, the same thing happened, but whenever a flood came it would leave its built-up bed, run over its banks, and cut new channels for itself in the lowest country it could find. There are many lakes and ponds well away from the present river that were obviously a part of the channel once.