It is with marked hesitation that I begin this chapter, because in it I must deal with an experience so contrary to every known law of physics as to seem impossible. Until this time, barring, of course, the mystery of the Dweller, I had encountered nothing that was not susceptible of naturalistic explanation; nothing, in a word, outside the domain of science itself; nothing that I would have felt hesitancy in reciting to my colleagues of the International Association of Science. Amazing, unfamiliar--_advanced_--as many of the phenomena were, still they lay well within the limits of what we have mapped as the possible; in regions, it is true, still virgin to the mind of man, but toward which that mind is steadily advancing. But this--well, I confess that I have a theory that is naturalistic; but so abstruse, so difficult to make clear within the short confines of the space I have to give it, so dependent upon conceptions that even the highest-trained scientific brains find difficult to grasp, that I despair. I can only say that the thing occurred; that it took place in precisely the manner I am about to narrate, and that I experienced it. Yet, in justice to myself, I must open up some paths of preliminary approach toward the heart of the perplexity. And the first path is the realization that our world _whatever_ it is, is certainly _not_ the world as we see it! Regarding this I shall refer to a discourse upon "Gravitation and the Principle of Relativity," by the distinguished English physicist, Dr. A. S. Eddington, which I had the pleasure of hearing him deliver before the Royal Institution.[1] I realize, of course, that it is not true logic to argue--"The world is not as we think it is--therefore everything we think impossible is possible in it." Even if it _be_ different, it is governed by _law_. The truly impossible is that which is outside law, and as nothing _can_ be outside law, the impossible _cannot_ exist. The crux of the matter then becomes our determination whether what we think is impossible may or may not be possible under laws still beyond our knowledge. I hope that you will pardon me for this somewhat academic digression, but I felt it was necessary, and it has, at least, put me more at ease. And now to resume.