higher sensitiveness. In either case the vision is the product of the
emergency, and is not repeated simply because the necessary conditions
are not repeated.

There remains, however, an irresolvable residuum of cases in which a
solitary instance occurs of the exercise of undoubted clairvoyance,
while yet the occasion seems to us wholly trivial and unimportant.
About these we can only frame hypotheses; the governing conditions are
evidently not on the physical plane, and a separate investigation of
each case would be necessary before we could speak with any certainty
as to its causes. In some such it has appeared that an astral entity
was endeavouring to make some communication, and was able to impress
only some unimportant detail on its subject--all the useful or
significant part of what it had to say failing to get through into the
subject's consciousness.

In the investigation of the phenomena of clairvoyance all these varied
types and many others will be encountered, and a certain number of
cases of mere hallucination will be almost sure to appear also, and
will have to be carefully weeded out from the list of examples. The
student of such a subject needs an inexhaustible fund of patience and
steady perseverance, but if he goes on long enough he will begin dimly
to discern order behind the chaos, and will gradually get some idea of
the great laws under which the whole evolution is working.

It will help him greatly in his efforts if he will adopt the order
which we have just followed--that is, if he will first take the
trouble to familiarize himself as thoroughly as may be with the actual
facts concerning the planes with which ordinary clairvoyance deals.
If he will learn what there really is to be seen with astral and
etheric sight, and what their respective limitations are, he will then
have, as it were, a standard by which to measure the cases which he
observes. Since all instances of partial sight must of necessity fit
into some niche in this whole, if he has the outline of the entire
scheme in his head he will find it comparatively easy with a little
practice to classify the instances with which he is called upon to
deal.

We have said nothing as yet as to the still more wonderful
possibilities of clairvoyance upon the mental plane, nor indeed is it
necessary that much should be said, as it is exceedingly improbable
that the investigator will ever meet with any examples of it except
among pupils properly