The very word spiritus suggests air in motion, and the very idea of abnormal power suggests the trembling and shaking of the place wherein it is present. Yet, on the other side, the 'cold non- natural wind' of seances, of Swedenborg, and of a hundred stories, old or new, is undeniably felt by some sceptical observers, even on occasions where no professional charlatan is engaged. As to the trembling and shaking of the house or hut, where the spirit is alleged to be, we shall examine some curious evidence, ancient and modern, savage and civilised. So of the other phenomena. Some seem to be of easy natural invention, others not so; and, in the latter case, independent evolution of an idea not obvious is a difficult hypothesis, while transmission from the Pole to Australia, though conceivable, is apt to give rise to doubt. Meanwhile, one phenomenon, which is usually said to accompany others much more startling, may now be held to have won acceptance from science. This is what the Dene Hareskins call the Sleep of the Shadow, that is, the Magical Sleep, the hypnotic trance. Savages are well acquainted with this abnormal condition, and with means of producing it, and it is at the bottom of all their more mysterious non-sympathetic magic. Before Mesmer, and even till within the last thirty years, this phenomenon, too, would have been scouted; now it is a commonplace of physiology. For such physical symptoms as introverted eyes in seers we need look no further than Martin's account of the second-sighted men, in his book on the Hebrides. The phenomenon of anaesthesia, insensibility to pain, in trance, is not unfamiliar to science, but that red-hot coals should not burn a seer or medium is, perhaps, less easily accepted; while science, naturally, does not recognise the clairvoyance, and still less the 'spiritual' attendants of the seer in the Sleep of the Shadow. Nevertheless, classical, modern, and savage spiritualists are agreed in reporting these last and most startling phenomena of the magic slumber in certain cases.