After Mark had settled in Hartford he formed a close friendship with his near neighbor Charles Dudley Warner; and in 1873 they joined forces in a novel, the ‘Gilded Age.’ They wrote it not so much in collaboration as in conjunction,—that is to say, each of the writers was responsible for the chapters he prepared himself; and there was no integrating co-ordination of their respective contributions. Mark was the author of more than half of the chapters; and he was the creator of the one outstanding character, Colonel Mulberry Sellers, an imaginative reproduction of a man he had known since boyhood, James Lampton. Mark began by writing the first eleven chapters, then Warner wrote two, Mark followed with two more; and thus they worked alternately. They labored, so Mark declared, “in the superstition that we were writing one coherent yarn, when I suppose, as a matter of fact, we were writing two incoherent yarns.” It was not long after the publication of their conjoint work that they were informed of the performance in San Francisco of a dramatization by one Gilbert S. Densmore, otherwise unknown to fame, the character of Colonel Sellers being impersonated by John T. Raymond. Action was at once taken to put a stop to this infringement on the copyright of the story. In the end a satisfactory arrangement was arrived at. Densmore was bought out; Warner, discovering that his share in the story had been but little drawn upon, relinquished any claim he might have; Mark made the piece over; and Raymond continued to play Colonel Sellers, under a contract which divided the profits between the author and the actor. For a season or two Mark’s agent travelled with the company and reported on a postal card every night the author’s share; and Howells has related how these welcome missives would come about dinnertime and how Mark would read them aloud in triumph. “One hundred and fifty dollars—two hundred dollars—three hundred dollars, were the gay figures which they bore and which he flaunted in the air before he sat down at table.” It is difficult now to determine how much of the dramatic skeleton Densmore had put together to enable Colonel Sellers to exhibit the facets of his lovable character, survived in the play which drew crowded houses one long winter in New York. Here Mark himself is the best witness in his own behalf; and his biographer has quoted from an unpublished letter a clear-cut statement: I entirely rewrote the play three separate and distinct times. I had expected to use little of [Densmore’s] language and but little of his plot. I do not think that there are now twenty sentences of Mr. Densmore’s in the play, but I used so much of his plot that I wrote and told him I should pay him about as much more as I had already paid him, in case the play proved a success. Paine has printed Densmore’s acknowledgment for this second payment, thanking Mark “for the very handsome manner in which you have acted in this matter.”