I repeat it—with accounts of this character, though in the highest degree acceptable, science cannot at present deal; and in proceeding now to attempt an explanation of the phenomena illustrated by the experiments of the English communication mentioned, I shall entirely leave out of consideration the cases that point to telepathic causes or clairvoyance in time and space. We have already made the acquaintance of some few theories which have arisen historically. Formerly, and even at the present day in fact, certain objects and qualities of objects were made accountable for the occurrence of striking hallucinations. The great cycle of legends that adhere to the magic mirror, has thus arisen. Often a pentahedronal quartz-crystal, often the fusion of the seven ancient metals into polished surfaces was supposed to possess especial virtue. Gregory, of Edinburgh, asserted that the phenomena were most easily produced by looking into a double-convex plate of zinc into the centre of which a small polished copper disk had been set. We now know that in the importance attached to these and similar directions the salient point was missed and an incidental factor pushed into the foreground. But in any event it is worthy of remark, that through belief in notions of this kind the seer gained a greater confidence in the success of his experiments. Even incorrect theories prove to be useful. When any one finally came into the possession of a famous magic stone, his firm belief in its powers induced a disposition to visions that perhaps never before existed in his organism to the same degree.