.

But to us as normal beings clairvoyance should appear a
potentially normal faculty, to be studied and pursued by methods
that are efficient while yet harmless; and this is the purport of the
present treatise. I will therefore ask the reader to follow me in
these pages with a mind divested of all disposition to the
supernatural.

CHAPTER IV.

PRELIMINARIES AND PRACTICE

The first consideration by those who would develop clairvoyance
by artificial aids is the choice of a suitable agent. It has been the
practice for many years to substitute the original beryl or "rock
crystal" by a glass ball. I admit that many specimens I have seen
are very creditable productions, but they are nevertheless quite
worthless from the point of view of those who consider material
agents to be important factors in the production of clairvoyance.
The glass ball may, however, very well serve the preliminary
essential of concentration, and, if the faculty of clairvoyance is at
all active, will be entirely effective as an agent.

Those who have any experience at all in this matter will allow
that the rock crystal exerts an influence of an entirely different
nature to that observable in the use of glass. Indeed, so far as
experiment serves us, it may be said that glass only produces
negative results and never at any time induced clairvoyance. If
this state followed upon the use of a glass ball I am sure that the
patient must have been naturally clairvoyant, in which case a
bowl of water, a spot upon a wall, a piece of polished brass or
copper, or a spot of ink would have been equally efficacious in
inducing the degree of hypnosis required. That glass spheres are
equally efficient as those of crystal is true only in two cases,
namely, when clairvoyance is natural, in which case neither need
be used; and when no results are observable after due experiment,
from which we may conclude either that the agent is unsuitable
or that the faculty is entirely submerged in that individual.

In hypnotic clairvoyance the glass ball will be found as useful a
"field" as the best rock crystal. Yet it does not follow that because
the crystal is highly odylic and glass altogether negative the
former will induce clairvoyance. My own first experience with
the crystal was entirely disappointing, while very striking results
followed immediately upon the use of a black concave mirror.

The mirror is usually circular in shape and about one-quarter-inch
curve