STORY OF THE DIPLOMATIST {56a}

For example, there is a living diplomatist who knows men and cities,
and has, moreover, a fine sense of humour. "My Lord," said a famous
Russian statesman to him, "you have all the qualities of a
diplomatist, but you cannot control your smile." This gentleman,
walking alone in a certain cloister at Cambridge, met a casual
acquaintance, a well-known London clergyman, and was just about
shaking hands with him, when the clergyman vanished. Nothing in
particular happened to either of them; the clergyman was not in the
seer's mind at the moment.

This is a good example of a solitary hallucination in the experience
of a very cool-headed observer. The _causes_ of such experiences are
still a mystery to science. Even people who believe in "mental
telegraphy," say when a distant person, at death or in any other
crisis, impresses himself as present on the senses of a friend, cannot
account for an experience like that of the diplomatist, an experience
not very uncommon, and little noticed except when it happens to
coincide with some remarkable event. {56b} Nor are such
hallucinations of an origin easily detected, like those of delirium,
insanity, intoxication, grief, anxiety, or remorse. We can only
suppose that a past impression of the aspect of a friend is recalled
by some association of ideas so vividly that (though we are not
_consciously_ thinking of him) we conceive the friend to be actually
present in the body when he is absent.

These hallucinations are casual and unsought. 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