Henry James's New York Edition Prefaces are collected in Volume XXXIII of The Complete Fiction of Henry James. The editor of that volume, Oliver Herford, has prepared the text for this Appendix, and has supplied essential annotations; more extensive notes can be found in The Prefaces.

The Princess Casamassima: NYE V, v–xxiii

The simplest account of the origin of “The Princess Casamassima” is, I think, that this fiction proceeded quite directly, during the first year of a long residence in London, from the habit and the interest of walking the streets. I walked a great deal—for exercise, for amusement, for acquisition, and above all I always walked home at the evening's end, when the evening had been spent elsewhere, as happened more often than not; and as to do this was to receive many impressions, so the impressions worked and sought an issue, so the book after a time was born. It is a fact that, as I look back, the attentive exploration of London, the assault directly made by the great city upon an imagination quick to react, fully explains a large part of it. There is a minor element that refers itself to another source, of which I shall presently speak; but the prime idea was unmistakeably the ripe round fruit of perambulation. One walked of course with one's eyes greatly open, and I hasten to declare that such a practice, carried on for a long time and over a considerable space, positively provokes, all round, a mystic solicitation, the urgent appeal, on the part of everything, to be interpreted and, so far as may be, reproduced. “Subjects” and situations, character and history, the tragedy and comedy of life, are things of which the common air, in such conditions, seems pungently to taste; and to a mind curious, before the human scene, of meanings and revelations the great grey Babylon easily becomes, on its face, a garden bristling with an immense illustrative flora. Possible stories, presentable figures, rise from the thick jungle as the observer moves, fluttering up like startled game, and before he knows it indeed he has fairly to guard himself against the brush of importunate wings.