The humor of Mark Twain is never forced. It bubbles up of its own accord, and is always fresh. In his recent books he shows less of genuine wit than in his earlier works perhaps, but yet his writings are always readable. He sent me, not long since, a printed slip of his biography, taken from Men of the Time, and on the margins of this appeared the following _bon mot_: . “MY DEAR CLEMENS: “I haven’t any humorous biography--the facts don’t admit of it. I had this sketch from Men of the Time printed on slips to enable me to study my history at my leisure. S. L. CLEMENS.” There is a popular feeling abroad in the land to the effect that Mark Twain is a very funny man, and that he is seldom sober. This is a grave mistake. Mr. Clemens is by nature a very serious, thoughtful man. True he seldom writes that which is not humorous, but occasionally he pens a very careful, serious communication, like the following for instance, which he addressed to a young friend of mine: “HARTFORD, January 16, 1881. “MY DEAR BOY:--How can I advise another man wisely, out of such a capital as a life filled with mistakes? Advise him how to avoid the like? No--for opportunities to make the same mistakes do not happen to any two men. Your own experiences may possibly teach you, but another man’s can’t. I do not know anything for a person to do but just peg along, doing the things that offer, and regretting them the next day. It is my way, and everybody’s. “Truly yours, S. L. CLEMENS.”