But between these and the dreams of sleep there is a kind of waking hallucinations which some people can purposely evoke.

Such are the visions of _crystal gazing_.
Among the superstitions of almost all ages and countries is the belief that "spirits" will show themselves, usually after magical ceremonies, to certain persons, commonly children, who stare into a crystal ball, a cup, a mirror, a blob of ink (in Egypt and India), a drop of blood (among the Maoris of New Zealand), a bowl of water (Red Indian), a pond (Roman and African), water in a glass bowl (in Fez), or almost any polished surface.

The magical ceremonies, which have probably nothing to do with the matter, have succeeded in making this old and nearly universal belief seem a mere fantastic superstition.

But occasionally a person not superstitious has recorded this experience.
Thus George Sand in her Histoire de ma Vie mentions that, as a little girl, she used to see wonderful moving landscapes in the polished back of a screen.

These were so vivid that she thought they must be visible to others.
Recent experiments have proved that an unexpected number of people have this faculty.