There is but one way to account for the fact that the man whom the world knew as Mark Twain—­dreamy, unpractical, and indifferent to details—­ever persisted in acquiring knowledge like that—­in the vast, the absolutely limitless quantity necessary to Mississippi piloting.  It lies in the fact that he loved the river in its every mood and aspect and detail, and not only the river, but a steam boat; and still more, perhaps, the freedom of the pilot’s life and its prestige.  Wherever he has written of the river—­and in one way or another he was always writing of it we feel the claim of the old captivity and that it still holds him.  In the Huckleberry Finn book, during those nights and days with Huck and Nigger Jim on the raft—­whether in stormlit blackness, still noontide, or the lifting mists of morning—­we can fairly “smell” the river, as Huck himself would say, and we know that it is because the writer loved it with his heart of hearts and literally drank in its environment and atmosphere during those halcyon pilot days.

So, in his love lay the secret of his marvelous learning, and it is recorded (not by himself, but by his teacher) that he was an apt pupil.  Horace Bixby has more than once declared: 

“Sam was always good-natured, and he had a natural taste for the river.  He had a fine memory and never forgot anything I told him.”

Mark Twain himself records a different opinion of his memory, with the size of its appalling task.  It can only be presented in his own words.  In the pages quoted he had mastered somewhat of the problem, and had begun to take on airs.  His chief was a constant menace at such moments: 

    One day he turned on me suddenly with this settler: 

    “What is the shape of Walnut Bend?”

He might as well have asked me my grandmother’s opinion of protoplasm.  I reflected respectfully, and then said I didn’t know it had any particular shape.  My gun-powdery chief went off with a bang, of course, and then went on loading and firing until he was out of adjectives....  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 is blotted out and gone.  But mind you, it hasn’t the same shape in the night that it has in the daytime.”

    “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——­”