The room in which the sitting takes place should be moderately warm, shady, and lit by a diffused light, such as may be obtained by a light holland blind or casement cloth, in the daytime. The subject should sit with his back to the source of light, and the illumination will be adequate if ordinary print can be read by it.
It is important that all persons sitting in the same room with the seer should be at least at arm's length from him.
Silence should be uniformly observed by those present, until the vision is attained.
It will then be found convenient to have two persons present to act as Interrogator and Recorder respectively.
The Interrogator should be the only person whose voice is heard, and it should be reduced to a soft but distinct monotone. The Recorder will be occupied in setting down in writing all questions asked by the Interrogator and the exact answers made by the seer. These should be dated and signed by those present when completed. It is perhaps hardly necessary to remark that precautions should be taken to prevent sudden intrusions, and as far as possible to secure general quiet without.
I may here interject an observation which appears to me suggestive and may prove valuable. It has been observed that the inhabitants of basaltic localities are more generally natural clairvoyants than others. Basalt is an igneous rock composed largely of augite and felspar, which are silicate crystals of calcium, potassium, alumina, etc., of which the Moonstone is a variety. The connecting link is that clairvoyance is found to be unusually active during and by means of moonlight. What psycho-physical effect either basalt or moonlight has upon the nervous system of impressible subjects appears to be somewhat obscure, but there is little difference between calcium light and moonlight, except that the latter is moderated by the greater atmosphere through which it comes to us. It is only when we come to know the psychological values of various chemical bodies that we can hope for a solution of many strange phenomena connected with the clairvoyant faculty. I recollect that the seeress of Prevorst experienced positive pain from the near presence of water during her abnormal phases. Reichenbach found certain psycho-pathological conditions to be excited by various metals and foreign bodies when brought into contact with the sensitive. These observations are extremely useful if only in producing an awareness of possible reasons for such disturbance as may occur in the conditions already cited.