Professor Zöllner also became a believer in Spiritualism, mainly through experiments with the American medium Mr. Slade. He published a work on the subject, in which he advances the theory, which has of late attracted so much attention, of a fourth dimension in space; that is, that, in addition to length, breadth, and thickness, bodies may have a fourth dimension, beyond the powers of human observation. The untying of knots in sealed ropes, passage of matter through matter, etc., he attempts to explain as possibly done by agents capable of working in this fourth dimension of matter. Science, however, is as little inclined to accept this theory as to accept that of spirit communication. Of the American scientific observers Professor Hare is far the most noted for his critical discernment, his accuracy of observation, and his obstinate determination not to be convinced that there was anything occult in these phenomena. He was remarkably skilful in the making of scientific apparatus, and he tested the phenomena received by a series of instruments of delicate construction and capable of exposing the least attempt at fraud. Those who were present at the circles with him declare that he would frequently make his appearance with a new instrument and a face full of grim expectancy that he would now baffle the powers that had baffled him on previous occasions, and that he would retire with a countenance of settled despondency as the unseen _something_ set at nought his deep-laid plans and secret hopes. It will suffice to say here that his experiments ended in his accepting the spiritual explanation of the phenomena and publishing a work on the subject. The same was the case with Judge Edmonds, from whose published work we may make a few quotations, as his high standing as a jurist and reputation for veracity and legal shrewdness make him a witness whose word would be accepted without question on any ordinary subject. He gives the following strange experience: "During the last illness of my revered old friend Isaac T. Hopper I was a good deal with him, and on the day when he died I was with him from noon till about seven o'clock in the evening. I then supposed he would live yet for several days, and at that hour I left to attend my circle, proposing to call again on my way home. About ten o'clock in the evening, while attending the circle, I asked if I might put a mental question. I did so, and I know that no person present could know what it was, or to what subject even it referred. My question related to Mr. Hopper, and I received for answer through the rappings, as from himself, that he was dead. I hastened immediately to his house, and found that it was so. That could not have been from any one present, for they did not know of his death, nor did they understand the answer I received. It could not have been the reflex of my own mind, for I had left him alive, and thought that he would live several days."