Fraud can be conscious, unconscious, or mixed. I have no need to say how frequent the first is, especially with paid mediums. Spiritistic reviews, notably the Revue Spirite, Revue Morale et Scientifique du Spiritisme, Light, Psychische Studien, give many examples of fraud discovered by spiritists themselves. Unconscious fraud is no less common than conscious fraud; as for the third, mixed fraud, this is also very often observed. _Conscious fraud._—(_a_) _Raps._ Nothing is easier to imitate. I have indicated the diverse ways of reproducing them artificially: gliding the finger or nail along the top of the table, with or without the help of resin; rapping with the feet; gliding the foot or dress—especially silk dresses—against the legs of table, etc. These diverse movements imitate feeble raps to perfection, if they be slowly made. For that reason I have always refused to consider raps as convincing when produced with any contact whatever. Consequently I exclude raps produced on the floor from those phenomena which have determined my conviction. Certain persons seem to be able to move their tendons at will, even making a considerable noise in that way. I observed this with a medical student who, by resting his elbow on the table, produced very sonorous raps; but the movement of his arm was easily seen. I know another person who could crack his joints at will. The play of the knee-joint has been especially incriminated by Mrs. Sidgwick in her article ‘The Physical Phenomena of Spiritualism’ (_Proceedings of the S.P.R._ xiii. 45). She recalls to mind the interpretations given by Drs. Lee, Flint, and Coventry, who observed Mrs. Kane and Mrs. Underhill, two of the famous Fox sisters. Mrs. Sidgwick experimented with the third sister, Mrs. Jencken, and accepted the explanation of the American doctors. For them, the double raps were produced by a rapid movement of dislocation and readjustment of the knee. By placing in such a position as to render that voluntary dislocation impossible, _e.g._ by making the medium sit down with outstretched legs and heels resting on a soft cushion, no raps were forthcoming. It is possible that the explanation of the American doctors may be true concerning the case examined by them. In those which I have studied, it is certainly not acceptable. I have obtained raps on a table without any kind of contact whatsoever. I have obtained them on the floor, by placing the medium in positions which excluded the play of articulation. The kind of fraud in question was not therefore in operation. I have even made some mediums sit on my knees when raps were forthcoming; I then made sure the raps were produced on the table, and that the latter was not touched. My conclusion as to the reality of the phenomenon of raps is the result of nearly two hundred observations.