It may be well that I should put a short preface to this book. In the summer of 1878 my father told me that he had written a memoir of his own life. He did not speak about it at length, but said that he had written me a letter, not to be opened until after his death, containing instructions for publication. This letter was dated 30th April, 1876. I will give here as much of it as concerns the public: "I wish you to accept as a gift from me, given you now, the accompanying pages which contain a memoir of my life. My intention is that they shall be published after my death, and be edited by you. But I leave it altogether to your discretion whether to publish or to suppress the work;-and also to your discretion whether any part or what part shall be omitted. But I would not wish that anything should be added to the memoir. If you wish to say any word as from yourself, let it be done in the shape of a preface or introductory chapter." At the end there is a postscript: "The publication, if made at all, should be effected as soon as possible after my death." My father died on the 6th of December, 1882...

(From Goodreads)