Old Times on the Mississippi

And then if you will go on until you know every street crossing, the character, size, and position of the crossing-stones, and the varying depth of mud in each of those numberless places, you will have some idea of what the pilot must know in order to keep a Mississippi steamer out of trouble. Next, if you will take half of the signs in that long street, and change their places once a month, and still manage to know their new positions accurately on dark nights. and keep up with these repeated changes without making any mistakes, you will understand what is required of a pilot’s peerless memory by the fickle Mississippi.