I will not stop to consider movements with contact. From a physical point of view they have no serious signification whatever. They are so easily explained by the combined, unconscious, muscular movements of the experimenters, that it is really not worth while stopping to examine them. The messages obtained by their intermedium may present an internal or clinical interest, but in that case they belong to the category of intellectual phenomena, properly so-called.

The first physical phenomena, which deserves attention, is that of ‘raps.’ It is generally the one most frequently obtained. We must, however, point out that the faculties of mediums are not identical: some produce chiefly physical, others chiefly intellectual phenomena. The former also manifest diverse qualities: some of them obtain raps, others movements, others luminous phenomena. Still in a general way ‘raps’ have seemed to me to be one of the simplest phenomena of a material order.

If we work with a physical medium of even only average force, raps will be heard after the third or fourth seance. They will be heard much sooner if we have a powerful medium.

As a rule, raps seem to resound on the top of the table; but it is not always so. They are frequently heard on the ground, on the sitters, or on the furniture, walls, or ceiling. The raps I have heard—of course I am speaking only of genuine raps—have resounded near the medium, as a rule, either on the table, floor, walls, or furniture in close proximity to him.

The simplest way to obtain raps is to proceed as I have directed in section ii. chapter 1. The experimenters, seated around a table, lay their hands upon it palm downwards, with outstretched fingers. This method is not, however, to be strongly recommended, for raps are easily imitated: and we must never lose sight of that fact when appreciating an experiment; further on, I will enumerate the usual fraudulent processes. Still, even when the hands are resting upon the table, raps can be obtained of sufficient sonority to exclude the hypothesis of fraud, if not absolutely, at least with much probability.

I have received raps in full light. I have received them so frequently in vivid light, that sometimes I cannot help wondering, whether darkness facilitates their production to the same extent as it may other phenomena. It is, however, allowable to suppose, that the energy which produces them prefers accumulating force in spots that are sheltered from strong light, e.g. under the table, or under the floor, or in shaded corners of the room. What makes me suppose so is this, I have frequently noticed that the raps burst forth under the medium’s hand, when they appeared to be produced on the top of the table.

Contact of the hands is unnecessary when sitting for raps. I have procured them quite easily, with several mediums, without such contact.

When we have succeeded in obtaining raps with contact, one of the best ways of obtaining them without contact is to let the hands rest for a certain time on the table, then to raise them very slowly, palms downwards, and the fingers loosely extended. Under such conditions, it seldom happens that raps do not continue to be heard for at least a short time. I need not say that experimenters should not only avoid contact of their hands with the table, but even of any part of their body or clothing. The contact of clothing with the table is sufficient to produce raps, which have nothing of a supernormal nature. We must be careful, therefore, that ladies’ dresses especially do not come into contact with the table; in taking these necessary precautions, raps can be obtained under most satisfactory and convincing conditions.

With certain mediums the energy liberated is great enough to act at a distance. I once heard raps upon a table which was nearly six feet away from the medium. On that occasion we had had a very short seance, and had left the table. I was seated in an armchair, the medium was standing by, talking to me, when a shower of raps suddenly resounded upon the table we had just left. The experimenters are all personally known to me, and I am persuaded that they are above suspicion; but this circumstance is quite insufficient in itself to entail a favourable conclusion of the phenomenon, for I cannot too strongly put experimenters on their guard against blindly confiding in their neighbours. Serious experimenters should exclude all susceptibility amongst themselves, and agree beforehand that reciprocal verification and control will be freely exercised without any one taking offence. In the case I am speaking of, the table on which the raps were heard was about six feet away from the medium and myself; it was daylight, towards five o’clock on a summer’s afternoon; the table had never been touched by the medium or the experimenters before the seance; the raps were loud, and were heard for several minutes.

I have had several opportunities of observing facts of this kind. Once, when travelling, I came across a medium among my fellow-travellers. He has not given me permission to name him, but I may say he is an honourable, highly-educated gentleman, occupying an official position. He had no suspicion of his latent faculties before experimenting with me. I obtained with him loud raps in buffets and restaurants. It would suffice to observe these raps produced under the conditions this medium offered me, to be convinced of their genuineness. The unusual noise attracted the attention of persons present and greatly embarrassed us: the result surpassed our expectations, for the more we were confused by the noise of our raps, the louder they became; it was as though some one of a teasing turn of mind was amusing himself at our expense.

I have also heard, when in company with a medium, some very fine raps given on the floor in museums before the works of old masters, and especially before religious pictures. I particularly remember the intensity of certain raps I once heard when standing before a painting representing the burial of Christ,—the work of a celebrated artist. I also heard some fine raps in a house which is celebrated as having been the last home of a famous writer; in the room in which he died, the raps were so loud as to attract the suspicious attention of the guardian.

I have also heard formidable raps with the two young girls, fourteen and fifteen years of age, who were called the Agen mediums. I observed these mediums at their own home, and I also had them twice at Bordeaux, when on each occasion they remained for nearly a month. The raps produced by them are interesting, but they do not seem to me to be demonstrative. One of these girls obtained raps on the floor under her feet; I verified the apparent immobility of the foot while the raps were being produced. When the two girls were in bed, loud raps were heard near their feet, seemingly given on the wood of their bed. We were able to observe the apparent immobility of the children. Raps were also given on the blankets; we could feel the vibrations when laying our hands on the blankets; the raps appeared to be produced under our hands. I have heard diverse noises with these children in obscurity, but I draw no conclusion therefrom. I found out that they were not always sincere, and that they had a tendency to take advantage of the confidence and friendliness of the people, with whom they were staying. They have simulated some of their phenomena, especially raps in the ceiling. I have never been able to persuade these young girls to experiment at a table with sufficient conditions of light. They were accustomed to go to bed in order to procure their raps. It is true I have heard these raps in daylight, but I consider other conditions were unsatisfactory on these occasions. I regretted exceedingly that these mediums showed so little good-will, for even putting aside the greater part of the suspicious phenomena they produced, there were still some which seemed to be worthy of further examination.

I have touched upon my observation of these children because it is instructive, although it may be negative from my point of view. It shows the inconveniences of a bad method of development. I have noticed that psychical phenomena has a great tendency to repeat itself, to follow a certain routine: they tend to turn round the same axis. The children of whom I have just spoken had been allowed to acquire the habit of going to bed, in order to obtain the sonorous phenomena they appeared to produce. Therefore they were able to obtain them only under those conditions. They have never given me a ‘rap’ by means of a table, and yet, I am inclined to think that they, or at least that one of them, had the constitution necessary for the emission of psychic force.

My failure with the Agen mediums was not altogether devoid of interest, for I gained experience, and experience is only acquired with time, patience, and multiplicity of observations. It is useful to be able to compare good, doubtful, and bad seances.

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.

Sometimes, but more rarely, I have heard them on cloth, on the medium’s or sitters’ garments, etc. I have heard them on pieces of paper placed on the seance table, on books, on the walls, on tambourines, on small wooden articles, and particularly on a planchette which was used for automatic writing. I have also observed very curious raps with a writing-medium:—when he wrote automatically, raps resounded with extreme rapidity at the end of his pencil. I can affirm that the pencil did not strike the table, for several times I very carefully put my hand on the opposite end of the pencil, and I was then able to verify that the sound was produced at the point of the pencil, the pencil remaining all the time, steadily and firmly, on the paper—the raps resounded on the wood of the table, and not on the paper. In this case, of course, the medium held the pencil in his hand.

Consequently, raps may be given upon various articles, with or without contact, and even at a certain distance from the medium. I have observed some which burst forth as far as nine feet away from the medium. I have not obtained any at a greater distance than nine feet, and it is not often I have been able to observe them at that distance. One of the most curious cases I have observed is the following:—I was experimenting in a room where there was a screen. The table was about nine feet away from this article. Very clear, distinct raps resounded on the floor behind the screen. It was broad daylight, but the raps were given on the shaded side of the screen.

I have frequently heard raps in the seance-cabinet, the medium seated in front of the curtains as indicated in section ii. chapter 1. Thus placed, raps are easily obtained behind the medium: they may be given on the floor, the wall, or on the articles placed in the cabinet. They are also frequently given outside the curtains, on the medium’s chair, or on the floor under him. When raps are obtained, it is very easy to study them by varying, in many satisfactory ways, the conditions of the experiment. This is one of the phenomena whose reality has been the most clearly demonstrated to me.

The variety of form the raps may take is not less than the diversity of objects upon which they may be given, or the places in which they may be heard. The sound of the usual rap, on a table, reminds you of the tonality of an electric spark, while of course there are many variations.

In the first place, we must note that the tonality of raps differs according to the object upon which they resound. It is easy to recognise by the sound if the raps are given on wood, paper, or cloth. This is an interesting demonstration, because it indicates that the sound is produced by the vibrations of the material substance. The material molecules of the object struck are therefore put into movement; they are not, however, always disturbed in the same way, for the tonality of the raps given on the same object is susceptible of great variety. The raps, instead of being sharp and short, may be dull and resemble the muffled sound of impact with some soft body: they may resemble the slight noises made by a mouse, a fret-saw, or the scratching of a finger-nail on wood or cloth: they may affect the most diverse modalities. Their rhythm is as varied as their tonality.

One of the most curious facts revealed by the observation of raps, is their relation with what I call the personification. Each personified individuality manifests its presence by special raps. In a series of experiments which have now lasted for more than two years, I have had frequent opportunity of studying raps personifying diverse entities. One of these entities called itself ‘John,’ Eusapia’s control, who has retained a friendly feeling for me, it appears, ever since my first experiments with the Neapolitan medium. ‘John’ manifests by short, sharp raps, so very like the manipulation of the Morse telegraph, that my co-experimenters and I wondered whether we were not actually listening to the usual Morse signals. Unfortunately none of us knew how to recognise letters by rhythm as exercised telegraphists can. A group, of four individualities, who call themselves the ‘Fairies,’ manifest their presence by raps resembling high, clear notes. These personifications are particularly interesting, and, further on, I will have occasion of relating how one of them showed herself to me. The four fairies are fond of mingling in the conversation, approving or disapproving of the ideas expressed by the experimenters. They appear to take considerable interest in the experiments, and I have often noticed that it sufficed—when the raps delayed in making themselves heard—to turn the conversation upon psychical phenomena, their probable explanation, their conditions of realisation, etc., in order to receive approving or disapproving raps at once. Sometimes the raps imitate a burst of laughter—this coincides either with an amusing story related by one of the sitters, or with some mild teasing. Another entity personifies a man for whom I had the deepest affection: these raps are graver in character. This personality seems to have the clairvoyant perspicacity and the kindheartedness of the man I knew. His intervention manifested itself under very curious circumstances, but of too private a nature to be made public. I will cite another personification of more recent appearance. It gives itself out to be the astronomer, Chappe d’Auteroche, and has related most accurately the details of his life and death in California. As a biographical notice concerning this learned man appears in several dictionaries, notably in Larousse, it is impossible to affirm that the irruption of this personification is supernormal. The raps which announce his presence are dull-sounding, and are given with a certain amount of force. In conclusion, light precipitated raps, weak but abundant, are the signals of certain personifications which we might call mar-joys—troublesome guests, whose unwelcome intervention spoils the experience.

Let it not be forgotten, that if I point out the connection existing between the personifications and the raps, it does not follow that I accept the reality of those personifications. I am making a statement, and I fill in all the details, so that experimenters, tempted to resume my observations, may know exactly what I have observed. So far, the personifications have not convinced me of their identity. It is true I act somewhat indifferently the rÔle of listener to their fatiguing and rambling conversations, and that I do all I can to bring them back to material phenomena, so much more important to me in that they are so much easier to verify. Were I, however, not to point out the rÔle which the raps play in relation to the personification, I would be omitting one of their most significant features, and would not be giving their exact physiognomy.

They manifest themselves, then, as the expression of a will and activity distinct from those of the observers. Such is the appearance of the phenomenon. A curious fact is the result—not only do the raps reveal themselves as the productions of intelligent action, they also manifest intelligence in response to any particular rhythm or code which might be demanded.

Often the different raps reply to one another; and one of the most interesting experiences one can have is to hear these raps clear and resonant, or soft and muffled, sounding simultaneously on the floor, table, furniture, etc.

I have had exceptionally good opportunities of studying very closely this curious phenomenon of raps, and I think I have arrived at some conclusions. The first and most certain is their undoubtedly close connection with the muscular movements of the sitters. I may sum up my observations on this point in the three following propositions:—

• 1. All muscular movements, however slight, are generally followed by a rap.
• 2. The intensity of the raps does not strike me as being in proportion with the movement made.
• 3. The intensity of the raps does not seem to me to vary proportionately according to their distance from the medium.

The following are the facts upon which I build my conclusions:—

I. I have frequently found that when the raps were feeble or interspersed, an excellent way of producing them was to form a chain of the sitters’ hands round the table. One of the sitters, without breaking the chain—which he avoids doing by taking in the same hand his neighbours’ right and left hands—makes, with his freed hand, circular sweeps or passes a little distance above the circle formed by the sitters’ outstretched hands. Having done this, the experimenter draws his hand towards the centre of the circle to a variable height, and makes a slight, downward movement with his hand; then he abruptly arrests the movement at about five or six inches away from the table, when a rap invariably follows, corresponding with the sudden cessation of the movement. It is exceptional when this process does not give a rap as soon as there is a medium in the circle who is capable, in however feeble a degree, of producing raps.

The same experiment can be made without touching the table, i.e. by forming the chain above the table. One of the sitters then experiments as in the preceding case.

This is not the only observation I have made. I have noticed that with mediums of decided power, it was unnecessary to adopt any special method for the production of raps, as they were forthcoming as soon as any sort of movement with hands or feet was executed. With strong mediums, it often suffices to move the hand above the table, to shake the fingers, to gently press the foot upon the ground, in order to determine the production of a rap.

Needless to say with some mediums raps are forthcoming without the execution of any movement whatsoever: with patience nearly all physical mediums can obtain raps without movement. But it seems as though the execution of a movement acted in the nature of a determining cause: the accumulated energy then receives a sort of stimulus, the equilibrium is disturbed by the addition of the excess energy unemployed in the movement, and a kind of explosive discharge of neuric force occurs, causing the phenomenon of raps. This is, however, only a working hypothesis.

The synchronism between the raps and the movements made by the sitters is very interesting, as it reveals the connection which exists between the organism of the experimenters and the phenomena observed. Richet has already pointed this out. Eusapia Paladino, unconsciously perhaps, employs a process analogous to that which I described a little further back. This synchronism may give, as it has given, equivocal phenomena, and may also give rise to many false accusations of fraud. This is perhaps how Dr. Hodgson comes to attribute certain raps produced by Eusapia Paladino at Cambridge, to the latter striking the table with her head. Of course, I am unable to affirm the reality of the raps heard at Cambridge, seeing I was not present at the sitting of the Sidgwick group. I can but say, that the reading of the few extracts of the procÈs verbaux of these seances—most incomplete extracts—does not by any means indicate, whether the movement of the Italian medium’s head was the fraudulent physical cause of the rap, or whether this movement was but a synchronous phenomenon.

I cannot help thinking that the Cambridge experimenters were either ill-guided, or ill-favoured, for I have obtained raps with Eusapia Paladino in full light, I have obtained them with many other mediums, and it is a minimum phenomenon which they could have, and ought to have obtained, had they experimented in a proper manner.

I will discuss these seances more fully further on.[4] Therefore, even in the appreciation of fraud, we must not forget to take into consideration the curious synchronism I am pointing out.

There is another useful observation to make known: namely that raps produced by synchronous movements can be produced by the sitters themselves. In many cases, I have seen experimenters, non-mediums, obtain louder raps than the medium; the presence of a medium, however, is necessary, for, the persons of whom I speak obtain no raps whatever when alone. Here is a subject for study which has not yet been touched upon.

Sometimes, in order to obtain raps, it suffices to touch the medium, or to make a slight movement with the hand above the table, or simply to place the palm of the hand gently on the table; this is an excellent way to obtain clear, decided phenomena. The table must be moved away from the medium in such a way that contact is impossible. The observer puts himself beside the medium, takes both his hands in one of his own, and moves the other slowly over the table, or even keeps it quite still above the table. Nothing is more demonstrative than this experiment. Let us remember I am speaking of experiments made in broad daylight.

II. Secondly, I have verified that the intensity of the raps is not in proportion with the synchronous movement. I am unable to affirm the accuracy of this statement with the same confidence as with the preceding one; but I have observed the fact in a great many circumstances. Thus, e.g. a very slight movement of the finger will sometimes determine a rap, quite as loud as the rap determined by the abrupt lowering of the whole arm.

Again, a simple muscular contraction also will bring about the realisation of the phenomenon, without the execution of any apparent movement.

This observation is of special interest, if I am not mistaken, for it tends to make one suppose that the energy which serves to produce the raps is independent of the movement executed in space, but is connected with the cause of that movement, i.e. with the nervous influx. It would be well if experimenters, more competent than I am in physiology, were to study these observations carefully; I sincerely hope this will be done some day. Richet might well undertake these researches, for no one is more competent than he is to analyse the facts I am pointing out.

I think there is a close connection between psychical phenomena and the nervous system. What I have just said about the production of raps by the simple contraction of a muscle under a voluntary nervous influx is one of the reasons upon which I base my hypothesis.

There are others. I have often questioned mediums about their sensations when the raps were being produced. They all acknowledged to a feeling of fatigue—of depletion—after a good seance. This feeling is perceptible even to observers themselves. I have tried to analyse my own sensations when the raps are heard; I have not arrived at any positive result. I cannot say I have any decided physical sensation; but my negative observation is only of interest, if compared with the different observations I made, in connection with the production of movements without contact.

One of the mediums, with whom some of my best and clearest raps were obtained, tells me he experiences a feeling akin to cramp in the epigastric region when the raps are particularly loud. This medium is a clever and highly-educated man, one quite capable of analysing his own symptoms. It seems to him as though something emanated from his epigastrum.

III. Regarding my third proposition—the intensity of the raps is not appreciably affected by distance—I have found that raps could occur as far as three yards away from the medium. The raps given at this distance were as loud and clear as those given close to the medium. This fact would at first seem to imply a difference between the action of psychic force and that of gravitation, light, heat or electricity, all of which act with an energy in inverse proportion to the square of distances. However, such a conclusion would be premature, for secondary centres of accumulation of energy may be formed at a distance from the medium. The term ‘accumulation of energy’ is very vague and may be incorrect, but I dare not give a more precise one, and confine myself to simply stating, that the existence of such centres of accumulation and emission seems indicated, by the manner in which the phenomena are obtained.

I have never verified any serious physical effects at a greater distance than that of ten feet. I will add that if the phenomena are not more intense, they are at least more frequent in the immediate neighbourhood of the medium.

Such are the observations I have been able to make. It may quite naturally occur to my readers to think I have been the victim of illusion or fraud. This is not the case, however.

There is no illusion, simply because nothing permits me to suppose I am the victim of illusion. This assertion is insufficient, I admit: we are bad judges of ourselves. And now I ought to say, that if up to the present I have always clearly distinguished between real facts and subjective impressions, I present, nevertheless, two phenomena which may render my testimony suspect. The first is hypnagogic hallucination, the second coloured audition. The latter is not very decided; sound simply awakens in me the idea of colour, not the visual sensation of colour. My chromo-phonetic scale is A, white; I, black; É, grey; E, blue; on, green; er, air, oeil, orange, etc.[5] This phenomenon was rather marked when I was a child; but, I repeat, the reading of vowels or diphthongs, or the audition of sounds has never awakened a complete sensation of colour; the idea only was evoked.

On the contrary, hypnagogic illusion is, with me, a decided phenomenon. The illusion is exclusively visual. I have carefully observed this interesting faculty on myself; it appears to me to have its origin in dream. It is a dream begun before sleep has taken complete possession of one. The hallucination disappears as soon as somnolence ceases. It is with extreme difficulty that I am able to retain—even for a second—a hypnagogic picture, when I regain complete consciousness; in spite of all my efforts, the picture fades away or changes form as soon as I fix my attention upon it. I have seldom been able to maintain the illusory impression.

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.

There is yet another way of obtaining fraudulent raps; this is by leaning more or less heavily on the table. When the top of the table is thin, or when the table is badly put together, or the parts have too much play, the variations of the pressure of the hand determine noises which greatly resemble raps.

Lastly, I have sometimes observed raps produced in a way which should be made known. Some people, by leaning the foot in a certain way, and by contracting the muscles of the leg, can imitate raps on the ground. This fact has been indicated especially in connection with the sinews of the musculus peronaeus longus. I observed a medical student, an incorrigible cheat and neurotic, who obtained sounds very similar to authentic raps by leaning his elbow on the table, and making certain movements with his shoulder. There are also some people who can make their joints crack at will.

But force of habit soon teaches how to ferret out fraud, when working in daylight or with good artificial light. Besides, the tonality of authentic raps is characteristic, and the method of simulation indicated at the beginning of these remarks, i.e. finger-gliding, is the only one able to reproduce some of the raps with even a fair amount of exactness.

It does not seem to me to be possible to simulate raps on the table, when they are produced without contact. It is easy to localise them, and auscultation of the table enables us even to perceive the vibrations of the wood. Precautions, easily taken, enable us to make sure of the absence of contact and communication between the experimenters and the table.

To sum up, I am certain—as far as it is reasonably possible to be certain of anything in such a matter—that knockings of variable rhythm and tonality are heard in the presence of certain persons—knockings or ‘raps’ which cannot be explained by any known process. They are heard at diverse distances; they often seem to obey the expressed wishes of the sitters, and to manifest a certain independent intelligence. On the other hand, their production appears to be intimately connected with the nerve-energy of the medium and the sitters.

I think I am able to express the foregoing conclusions with certainty and confidence.

[4] See Appendix B.