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.