"Don't speak," he repeated, "but write, litera scripta manet, you will be believed sometime. But meanwhile you can take as your motto that verse in Virgil about the gate of ivory, and that will save you from being thought mad. You have a knack of the pen, Bob, you ought to try it."
"Well," said I, "let it be a joint concern between you and me, and I'll do my best."
Then we lit our pipes and walked home, and settled the matter in a very few words on the way. I was to write, but all I should write was to be read over to Jack, who should correct and supplement it from his own memory. And no account of anything which was witnessed by both of us was to stand finally unless it was fully vouched for by the memory of both. Thus for any part of the narrative which would concern one of us only that one should be alone responsible, but for all of it in which we were both concerned there should be a joint responsibility.
Out of this agreement comes the following history, and thus it happens that it is told in the first person singular, although there are two names on the title-page.