For all his exuberance, in short, he was not, on the whole, happy in his work; almost from the beginning of his career we note in him an increasing, distaste for this literary journalism which he would hardly have experienced if he had not been intended for quite another life. We remember that cry of distress when he was setting out on the _Quaker City_ excursion, that cry which must have seemed so fantastically meaningless to those who read his letter: "I am so worthless that it seems to me I never do anything or accomplish anything that lingers in my mind as a pleasant memory.... An accusing conscience gives me peace only in excitement and restless moving from place to place." What was it but the conscience of the artist in him, lulled into a fitful sleep by the applause of all America before it had ever been able quite to penetrate into the upper layers of his mind? Mr. Paine has noted the change in tone between the first and second parts of "Life on the Mississippi," written with an interval of twelve years, the change from "art" to "industry," the difference "between the labors of love and duty": he avers that the second half might have been as glamorous as the first if Mark Twain had revisited the river eight or ten years earlier, "before he had become a theoretical pessimist, and before the river itself had become a background for pessimism." Mr. Paine would have his task explaining, in that connection, the difference between "theoretical" pessimism and pessimism of the other sort! For it was just so between "The Innocents Abroad" and "A Tramp Abroad"; it was even more so between "A Tramp Abroad" and "Following the Equator": "In the 'Tramp,'" says Mr. Paine, "he has still the sense of humor, but he has become a cynic; restrained, but a cynic none the less." All that descriptive writing in which alone, perhaps, he could count upon an absolutely certain financial success--how repellant it became to him as time went on! Watch him guilefully trying to wriggle out of the self-imposed task of "A Tramp Abroad." He tells his friend Twitchell that he has lost his Swiss note-book, and, who knows? perhaps he won't have to write the book, after all. Then the note-book comes to light, and he is plunged in gloom: "I was about to write to my publisher and propose some other book, when the confounded thing turned up, and down went my heart into my boots." It seemed to him, says Mr. Paine, "that he had been given a life-sentence." And to what does he turn for relief? "The Prince and the Pauper," which he lingers over and cannot bear to finish, telling Mr. Howells that, after that "veritable nightmare" of "A Tramp Abroad," nothing can diminish his jubilant delight in writing it. He is a child among children again, doing a task that almost any gifted child might have done, something that is for him the equivalent of a charade, a pretty game with his little daughters, and basking for the moment in the approval of his wife.