The observation of the facts resumed in this chapter reveals another circumstance which deserves pointing out. This is the apparent conductibility of certain bodies for the force employed. I gave some examples: table-linen, wood, dresses, etc. I related having often seen women-mediums’ dresses bulge out and approach the table, when the phenomenon was being produced; the sensitive’s feet remained visible, and, in view of the conditions under which I have been able to test this phenomenon, I consider as absurd the idea that an artificial hand or foot was introduced, as imagined by Dr. Hodgson to explain away this fact with Eusapia. I have frequently obtained movements without the contact of the medium’s dress, but I have certainly noticed that this contact facilitates the realisation of the movement. Darkness favours it also; there is no doubt about this. Of course I am putting aside the greater facilities obscurity offers for the execution of fraudulent phenomena; and though, in this book, I have only taken into account phenomena observed in full light, I have often experimented in obscurity; and it appears to me certain, that total darkness is one of the conditions for the maximum development of the liberated energy. The action of light is interesting to note. I have already stated that the dynamic agency of psychical phenomena appeared to me to be analogous with the nervous influx, and that the table seemed to play the rôle of condenser. In that hypothesis, light would act like certain rays of cathodic origin, which discharge the electricised condensers placed in their vicinity. The study of the influence of light upon telekinetic phenomena will certainly enable us to learn their cause. The little we already know permits us to suspect that the telenergic force ought to have some _rapport_ with light and electricity, at least in that which concerns the amplitude of vibrations. The study of this _rapport_ can only be taken up by an experienced physicist. It will require delicate methods and special instruments, and I earnestly hope it will soon be seriously undertaken. As for those who confine themselves, as I do, to simply seeking whether the facts be real or not, they should avoid working in obscurity. Light may hamper the production of telekinetic movements, but it will not prevent it. Experimenters should accustom themselves to holding their seances in the daytime, or in a light which is sufficient to permit of reading small print. Above all things, it is necessary to be personally convinced of the reality of the facts; and this conviction is not so easily acquired, when the experiment is made in obscurity.