The Mississippi River, with its branches, drains the larger part of the whole United States,--that is, from the Alleghanies on the east to the Rockies on the west. The main stream, 4200 miles long, and in some places over a mile wide, flows along with tremendous force, ceaselessly eating away its yellow clay banks. The water, full of sediment, is of a thick dull brown color. The clay that it washes off in the bends it deposits on the juts of land, thus forming greater and greater curves; so that often the distance between two points is very much less by land than by water. Sometimes there are only a few yards across the neck of a peninsula, around which the channel distance is many miles; and on one side the level of the river is several feet higher than on the other. Gradually the water keeps eating its way, until it forces a passage through the neck, and then the torrent rushes through in a cascade, with a roar that can be heard for miles. The banks dissolve like sugar, and the next day steamboats can cross where the day before were fields and may be houses. Besides this, the current is constantly washing away and building up not only hidden bars on the river bottom, but even islands above its surface. In the fall and in the spring it rises with such terrifying rapidity that some years it quickly overflows its banks in certain reaches till it is sixty miles wide. Houses and trees torn from their places, and wrecks of boats, float or protrude from the bottom of this brown lake. And when the flood subsides, the current often chooses a new and changed channel. Amid the ever-varying dangers of such a river the only safety for steamboats is in a race of pilots so learned and so alert as to have the shifting bars and courses always in their minds. In 1839, when steamboats were the only means of rapid transit in the West, when there were more of them in the harbor of the little town of Saint Louis than to-day when it is a great city, this class of pilots was a large and a very respectable one. Much of their knowledge of the river was what young Eads learned while he was a clerk among them; and as time went on, he came to realize that although the Mississippi seems so capricious in its terrible games that one would think them the result of chance, yet in truth, they "are controlled by laws as immutable as the Creator."