To string incongruities and absurdities together in a wandering and zometimes purposeless way, and seem innocently unaware that they are absurdities, is the basis of the American art [of the humorous story]…Another feature is the slurring of the point. A third is the dropping of a studied remark apparently without knowing it, as if one were thinking aloud. The fourth and last is the pause.

Mark Twain, from How to Tell a Story. A wonderful-looking edition scanned by Google Books happens to be missing many pages. The quote pops up again in The Rotarian in 1937, with A Chuckle Girdles the World by George Vincent, who suggested “humor is our great protection against fanaticism.”

Twain proposed to differentiate the American art of the humorous story from the English comic story, and the French witty story. These depend on the matter of telling, and the American depends on the manner of telling. Of the American: “This is art–and fine and beautiful, and only a master can compass it; but a machine could tell the other story.”