Among my most doubtful experiences, whose recital may be as instructive as the foregoing, I will choose, for brief discussion, a recent series of seances which I held at Bordeaux. Some of the phenomena I observed seem to me difficult to explain by fraud, especially lights which floated about the seance-room; but the greater part of the motor phenomena was simulated. The personification had the habit of demanding total darkness, and as I was chiefly interested in luminous phenomena, I saw no inconvenience in putting out the lights. The personification, which made this request, was probably the personal consciousness of one of the sitters. As soon as the lights were extinguished, the raps became noticeably louder. Many of them were certainly the work of two of our number—I have not been able to analyse the mental state of these two young men: one of them, who is neurasthenic, acted perhaps unconsciously. Nevertheless, though I observed the whims of these two men with interest and attention, I noticed, at the same time, that raps were forthcoming in _total obscurity_ when I made imperceptible movements, _e.g._ when I gently blew on the table, or when I pressed the hand of one of my neighbours whose sincerity I could vouch for. There was always this synchronism, which I have already pointed out, between the muscular movement and the rap. Without being able to affirm it absolutely, I think I may say that my co-experimenters were not aware of the slight movements I made with my feet, hand, finger, or breath. In these sittings, otherwise bearing a most suspicious character, there was, therefore, a residue of facts worthy of attentive analysis. I was unable to make this analysis, having shortly afterwards ceased to experiment with the group, which these young men frequented. In some respects I am sorry for it, as the observation of this parcel of truth, and even of the two fraudulent experimenters themselves, was interesting from various points of view. I will now reconsider the experiments I first touched upon—viz. those conducted in full light—the only ones upon which I establish my opinion. I have indicated as fully as possible the conditions under which I have been able to observe raps. The raps most commonly heard are those given with contact on the table or floor, and then those which are given at some distance from the experimenters.