It was in February, 1885, that I entered into negotiations, with Mr. Harry Furniss, for illustrating the book. Most of the substance of _both_ Volumes was then in existence in manuscript: and my original intention was to publish the _whole_ story at once. In September, 1885, I received from Mr. Furniss the first set of drawings—the four which illustrate “Peter and Paul” (see I. pp. 144, 147, 150, 154): in November, 1886, I received the second set—the three which illustrate the Professor’s song about the “little man” who had “a little gun” (Vol. II. pp. 265, 266, 267): and in January, 1887, I received the third set—the four which illustrate the “Pig-Tale.” So we went on, illustrating first one bit of the story, and then another, without any idea of sequence. And it was not till March, 1889, that, having calculated the number of pages the story would occupy, I decided on dividing it into _two_ portions, and publishing it half at a time. This necessitated the writing of a _sort_ of conclusion for the first Volume: and _most_ of my Readers, I fancy, regarded this as the _actual_ conclusion, when that Volume appeared in December, 1889. At any rate, among all the letters I received about it, there was only _one_ which expressed _any_ suspicion that it was not a _final_ conclusion. This letter was from a child. She wrote “we were so glad, when we came to the end of the book, to find that there was no ending-up, for that shows us that you are going to write a sequel.” It may interest some of my Readers to know the _theory_ on which this story is constructed. It is an attempt to show what might _possibly_ happen, supposing that Fairies really existed; and that they were sometimes visible to us, and we to them; and that they were sometimes able to assume human form: and supposing, also, that human beings might sometimes become conscious of what goes on in the Fairy-world—by actual transference of their immaterial essence, such as we meet with in ‘Esoteric Buddhism.’ I have supposed a Human being to be capable of various psychical states, with varying degrees of consciousness, as follows:— (_a_) the ordinary state, with no consciousness of the presence of Fairies; (_b_) the ‘eerie’ state, in which, while conscious of actual surroundings, he is _also_ conscious of the presence of Fairies; (_c_) a form of trance, in which, while _un_conscious of actual surroundings, and apparently asleep, he (i.e. his immaterial essence) migrates to other scenes, in the actual world, or in Fairyland, and is conscious of the presence of Fairies. I have also supposed a Fairy to be capable of migrating from Fairyland into the actual world, and of assuming, at pleasure, a Human form; and also to be capable of various psychical states, viz. (_a_) the ordinary state, with no consciousness of the presence of Human beings;