I consider it necessary to declare for the last time that these psychometric phenomena, astonishing though they appear at first, are known, proved and certain and are no longer denied or doubted by any of those who have studied them seriously. I could have given full particulars of a large number of conclusive experiments; but this seemed to me as superfluous and tedious as would be, for instance, a string of names of the recognized chemical reactions that can be obtained in a laboratory. Any one who pleases is at liberty to convince himself of the reality of the facts, provided that he applies to genuine mediums and keeps aloof from the inferior "seers" and especially the shams and imposters who swarm in this region more than in any other. Even with the best of them, he will have to be careful of the involuntary, unconscious and almost inevitable interference of telepathy, which is also very interesting, though it is a phenomenon of a different class, much less surprising and debatable than pure psychometry. He must also learn the art of interrogating the medium and refrain from asking incoherent and random questions about casual or future events. He will not forget that "clairvoyance is strictly limited to the perception of human personality," according to the role so well formulated by Dr. Osty. Experiments have been made in which a psychometer, on touching the tooth of a prehistoric animal, saw the landscapes and the cataclysms of the earth's earliest ages displayed before his eyes; in which another medium, on handling a jewel, conjured up, it would seem with marvellous exactness, the games and processions of ancient Greece, as though the objects permanently retained the recollection or rediscovered the "astral negatives" of all the events which they once witnessed. But it will be understood that, in such cases, any effective control is, so to speak, impossible and that the part played by telepathy cannot be decided. It is important, therefore, to keep strictly to that which can be verified. Even when thus limiting his scope, the experimenter will meet with many surprises. For instance, though the revelations of two psychometers to whom the same letter is handed in succession most often agree remarkably in their main outlines, it can also happen that one of them perceives only what concerns the writer of the letter, whereas the other will be interested only in the person to whom the letter was addressed or to a third person who was in the room where the letter was written. It is well to be forearmed against these first mistakes, which, for that matter, in the frequent cases where strict control is possible, but confirm the existence and the independence of the astounding faculty. 11