Examples of the poignancy of expression, with which Mark Twain spurs his readers into a proper appreciation of what he is telling them, are too abundant for further reference, but although he uses them so easily, he does not always find them necessary. Some of the funniest passages in his later works, as well as in those by which he made his reputation, contain not a flash of wit nor any unusual expressions. A combination is presented in the plainest and simplest way, and as the substances are poured together the humour effervesces, not in the author's story, but in the 'reader's mind. The author draws out the wit of his readers as a magnet draws needles from a cushion.Mark Twain somewhere declared that there were only thirty-five varieties of joke known to the human race. He has practised most of these at one time or another—sometimes under dreary circumstances enough.