We must not conclude, that I am incompetent to distinguish a real phenomenon from a false one, because of the existence in myself of these two subjective phenomena. I have indicated the results of my self-observation in order to be thoroughly sincere and complete, for I have the keenest desire to be an accurate witness. I do not think, however, that the observations I have been able to make upon myself are really of a nature to cast suspicion upon my faculties of observation. Quite the contrary, I should say; because my personal experience enables me to recognise hypnagogic hallucinations, and, further on, I will point out some phenomena which seem to me to be closely connected with these hallucinations; but as for raps, they have quite a different character, and their objectivity appears quite certain to me. I will add that every one present can and does hear them. Let me recall to mind what I said about the raps I heard in railway refreshment rooms, restaurants, and other public places. All who were in the same room showed, by their demeanour, that they too heard the raps. This circumstance suffices to exclude the hypothesis of hallucination. I propose registering these raps in a phonograph; this will be the _experimentum crucis_ as far as their objectivity is concerned. I have no manner of doubt whatsoever upon the authenticity of raps, a phenomenon I have heard so frequently, and under such diverse and excellent conditions. I have also taken care to study the different ways of simulating raps,—and these are indeed manifold. The simplest and most perfect method is to gently glide—an imperceptible movement—the finger-tips along the table. The results are better when the finger is dry, when the natural grease has been previously removed by turpentine or benzine: resin is good, but leaves traces. Under these conditions, slight but clear raps may be obtained. The movement of the finger is so slow, that, unless forewarned, no one can discover it; but, with attentive observation, a slight vibration of the finger may be perceived when the raps burst forth. They can also be simulated with the finger-nails, but this process is easy to unmask. The trickster finds greater security in darkness, where he has resources other than those just mentioned. In obscurity he can easily imitate the raps which resound on the floor; _e.g._ he can produce dull raps by skilfully striking his foot against the legs of the table or on the floor; he can simulate the sharp, quick raps by allowing his boot to glide slowly along the feet of the table or chair. Raps are also very easily simulated by a gentle rubbing of clothing or linen, especially shirt-cuffs. We should beware of this, for raps can thus be produced by slow unconscious movements, and the good faith of the experimenters may be involuntarily taken by surprise.