If we desire a concrete instance of this omission of an important detail, we may turn once more to Dr. Furness's narrative. Certain highly intelligent observers had described to him the marvelous accomplishments of a Boston medium; and this is his own account: "There are two tables in the room of séance, at one of which sits the medium, at the other, the visitor. The visitor at his table writes his question in pencil at the top of a long slip of paper, and, after folding over several times the portion of the slip on which his question is written, gums it down with mucilage and hands it to the medium, who thereupon places on the folded and gummed portion his left hand, and in a few minutes with his right hand writes down answers to the concealed questions; these answers are marvels of pertinency, and prove beyond a cavil the clairvoyant or spiritual powers of the medium." Dr. Furness went to the medium, prepared his slip of paper about as described, and thus continues: "As soon as he took his seat, and laid the strip on his table before him, I rose and approached the table so as to keep my paper still in sight; _the row of books entirely intercepted my view of it_. The medium instantly motioned to me to return to my seat, and, I think, told me to do so. I obeyed, and as I did so could not repress a profound sigh. Why had no one ever told me of that row of books?" III I have thus passed in review a series of facts and considerations in pursuance of the general inquiry as to why the manifestations produced in evidence of spirit agency deceive, and as to the origin of the vast testimony in favor of spiritualistic marvels. It is not necessary for the purposes of the psychological discussion to demonstrate that all such manifestations are fraudulent; it is not even necessary--although with limitless time and energy it might be desirable--to examine all of the various kinds of manifestations which the ingenuity of mediums has devised, or which have been presented through mediumistic agency.[8] All that is necessary is to examine a sufficient number of manifestations of acknowledged standing and repute among spiritualists,--manifestations, be it clearly understood, which have actually brought hundreds and thousands of converts to its ranks, which have been persistently brought forward as indisputable evidence of supernatural agency--and to show that in reference to these, actual and extensive deception has taken place. It would not be proper to declare that at this point the psychologist's interest ends; for the centre of interest in such problems may shift from one point to another. The central point in the present discussion, however, is not what is the evidence in favor of the spiritualistic hypothesis logically worth,--although the considerations here presented have obvious and radical bearings upon that question. If that were our quest, we should put the spiritualists upon the defensive; for the burden rests upon them