You see this has got to be learned.... A clear starlight night throws such heavy shadows that if you didn't know the shape of a shore perfectly you would claw away from every bunch of timber because you would take the black shadow of it for a solid cape; and you see you would be getting scared to death every fifteen minutes by the watch. You would be fifty yards from shore all the time when you ought to be within fifty feet of it. You can't see a snag in one of those shadows, but you know exactly where it is, and the shape of the river tells you when you are coming to it. Then there's your pitch-dark night; the river is a very different shape on a pitch-dark night from what it is on a starlight night. All shores seem to be straight lines, then, and mighty dim ones, too; and you'd run them for straight lines only you know better. You boldly drive your boat right into what seems to be a solid, straight wall (you knowing very well that in reality there is a curve there) and that wall falls back and makes way for you. Then there's your gray mist. You take a night when there's one of these grisly, drizzly, gray mists, and then there isn't any particular shape to a shore. A gray mist would tangle the head of the oldest man that ever lived. Well, then, different kinds of moonlight change the shape of the river in different ways.... You only learn the shape of the river; and you learn it with such absolute certainty that you can always steer by the shape that's in your head and never mind the one that's before your eyes. ¹ ¹ Mark Twain, Life on the Mississippi, pp. 103-04. No wonder that the two hundred miles of the Mississippi from the mouth of the Ohio to St. Louis in time contained the wrecks of two hundred steamboats.