He was assisted, from time to time, in his investigations by Professors Weber, Fechner, and Scheibner all of whom were men of considerable eminence in one branch or another of mathematical or physical science. The medium in whose presence the phenomena were produced was the well-known "Dr." Slade. This medium has been demonstrated to have resorted to fraud with a certainty that admits of no dispute. But, as Mr. Hereward Carrington points out, we ought not to allow this fact to influence us in the consideration of any particular case. In the first place it is fairly certain that mediums who are capable of producing genuine phenomena under suitable conditions are also liable to resort to trickery when the genuine thing does not come off. (Cp. the case of Eusapia Palladino.) In the second, too great a reliance on antecedents is apt to produce an unreliable _a priori_ prejudice. Every case should be considered on its merits alone and the medium's past history should only be allowed to influence our judgment if it can be shown that fraud has not been rigorously excluded and that the only argument against it is the argument from moral integrity. In this case the argument from integrity is obviously inadmissible and as a matter of fact the precautions taken to guard against fraud were so very inadequate that we cannot accept the experiments in question as worth anything at all from the scientific point of view. Zöllner's account of his experiments is to be found in his book "Transcendental Physics," translated into English by Mr. C.C. Massey in whom the author found an able and enthusiastic champion against his many critics. Among the more important of his experiments were: Production of knots in an endless string. Slate writing under "test" conditions. Disappearance and reappearance of solid objects. Coins transferred from closed and fastened boxes. Other instances of the apparent penetration of matter by matter. The careful study of this book is of the greatest value as an exercise in the criticism of evidence and as a guide for anyone who proposes to study such matters at first hand. I do not think that I can illustrate my meaning better than by a description of my own impressions in connection with the book. When I first read it I was much impressed by the scientific eminence of those who bore witness to the authenticity of the events described. I reflected that here we had a Physicist of no mean order, assisted by other scientists of European reputation, men trained, presumably, in the art of exact observation and not likely to be deceived by the manipulations of a conjuror. Surely we must believe their testimony if we are to assign any value to human evidence at all!