astronomy at the University of Leipsic, undertook to prove that
certain (so-called) psychic phenomena were susceptible of explanation
on the hypothesis of a four-dimensional space. He used as
illustrations the phenomena induced by the medium Henry Slade. By
the irony of events, Slade was afterward arrested and imprisoned for
fraud, in England. This fact so prejudiced the public mind against
Zöllner that his name became a word of scorn, and the fourth dimension
a synonym for what is fatuous and false. Zöllner died of it, but
since his death public opinion has undergone a change. There is a
great and growing interest in everything pertaining to the fourth
dimension, and belief in that order of phenomena upon which Zöllner
based his deductions is supported by evidence at once voluminous and
impressive.

It is unnecessary to go into the question of the genuineness of the
particular phenomena which Zöllner witnessed. His conclusions are
alone important, since they apply equally to other manifestations,
whose authenticity has never been successfully impeached. Zöllner's
reasoning with regard to certain psychic phenomena is somewhat along
the following lines.


APPARITIONS

_The intrusion (as an apparition) of a person or thing into a
completely enclosed portion of three-space; or contrariwise, the
exit (as an evanishment) out of such a space_.

Because we lack the sense of four-dimensional space, we must here
have recourse to analogy, and assume three-dimensional space to be