My little book seems scarcely to admit of prefatory words: either it
will speak for itself, or all my additions must fail to speak for it.
Its reappearance, however, in an American edition, gives me a welcome
opportunity of acknowledging the courtesy and liberality of Messrs.
Roberts Brothers, who have arranged with me and with my kind friend and
publisher, Mr. Macmillan, to bring it before the American public.