I had learned long ago that he only carried just so many rounds of ammunition, and was sure to subside into a very placable and even remorseful old smooth-bore as soon as they were all gone.  That word ‘old’ is merely affectionate; he was not more than thirty-four.  I waited.  By and by he said—­

’My boy, you’ve got to know the shape of the river perfectly.  It is all there is left to steer by on a very dark night.  Everything else is blotted out and gone.  But mind you, it hasn’t the same shape in the night that it has in the day-time.’

‘How on earth am I ever going to learn it, then?’

’How do you follow a hall at home in the dark.  Because you know the shape of it.  You can’t see it.’

’Do you mean to say that I’ve got to know all the million trifling variations of shape in the banks of this interminable river as well as I know the shape of the front hall at home?’

’On my honor, you’ve got to know them better than any man ever did know the shapes of the halls in his own house.’

‘I wish I was dead!’

‘Now I don’t want to discourage you, but—­’

‘Well, pile it on me; I might as well have it now as another time.’

’You see, this has got to be learned; there isn’t any getting around it.  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 see—­’

’Oh, don’t say any more, please!  Have I got to learn the shape of the river according to all these five hundred thousand different ways?  If I tried to carry all that cargo in my head it would make me stoop-shouldered.’

’No! 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.’