This search for evidences of hyper-dimensionality in the universe accessible to our senses is like looking, not for a needle in a haystack, but for a haystack in a needle--for the greater in the less. From the purely physical evidences, all that can with certainty be said is that the hypothesis is not inconsistent with the facts of science or its laws; that it is being verified and rendered more probable by the investigations of science; that it is applicable to the description or explanation of all the observed phenomena, and assigns a cause fully adequate to have produced them. Now there is an order of phenomena that we call psychic. Because they are phenomenal they cannot occur outside of time and space altogether; because they are psychic they defy explanation in terms of the space and time of every-day life. Let us next examine these in the light of our hypothesis. IV TRANSCENDENTAL PHYSICS ZÖLLNER In the year 1877, Johann Friedrich Zöllner, professor of physics and 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_.