First, light, of suitable wave-length, i.e. suitable color, and let me say here, once and for all, that I have proved conclusively for myself that darkness is not necessary, provided that one is experimenting with a sensitive who has been trained to sit always in the light.
On two occasions I have witnessed materializations in daylight; and neither of Sir William Crookes's sensitives—D. D. Home or Florrie Cook (Mrs. Corner)—would ever sit in darkness, the latter—with whom I carried out a long series of experiments—invariably stipulating that a good light should be used during the whole time that the experiment lasted, as she was terrified at the mere thought of darkness.
I find that sunlight, electric light, gas, colza oil, and paraffine are all apt to check the production of the phenomena unless filtered through canary-yellow, orange, red linen or paper—just as they are filtered for photographic purposes—owing to the violent action of the actinic (blue) rays which they contain (the rays from the violet end of the spectrum), which are said to work at about six hundred billions of vibrations per second. But if the light is filtered in the way that I have described, the production of the phenomena will commence at once, the vibrations of the interfering rays being reduced, it is said, to about four hundred billions per second or less.
In dealing with materializations we are apt to overlook the fact that we are investigating forces or modes of energy far more delicate than electricity, for instance. Heat, electricity, and light, as Sir William Crookes tells us, are all closely related; we know the awful power of heat and electricity, but are only too apt to forget—especially if it suits our purpose to do so—that light too has enormous dynamic potency; its vibrations being said to travel in space at the incredible speed of twelve million miles a minute;[15] and it is therefore only reasonable to assume that the power of these vibrations may be sufficient to interfere seriously with the more subtle forces, such as those which we are now investigating.
Secondly, we require suitable heat vibrations, and I find that those given off in a room either warmed or chilled to sixty-three degrees are the very best possible; anything either much above this, or more especially, much below this, tending to weaken the results and to cheek the phenomena.
Thirdly, we require suitable musical vibrations, and, after carrying out a long series of experiments with musical instruments of all kinds, I find that the vibrations given off by the reed organ—termed "harmonium" or "American organ"—or by the concertina, are the most suitable, the peculiar quality of the vibrations given off by the reeds in these instruments proving to be the most suitable ones for use during the production of the phenomena; although on one or two occasions I have obtained good results without musical vibrations of any kind, but this is rare.
Fourthly, we require the presence of a specially organized man or woman, termed the sensitive, one from whom it is alleged a portion of the matter used by the entity in the building up of its temporary body can be drawn, with but little chance of injury to their health. This point is one of vital importance, we are told, for it has been proved by means of a self-registering weighing-machine on which he was seated, and to which he was securely fastened with an electrical apparatus secretly hidden beneath the seat, which would at once ring a bell in an anteroom if he endeavored to rise from his seat during the experiment, that the actual loss in weight to the sensitive, when a fully materialized entity was standing in our midst, was no less than sixty-five pounds!
Before employing any person, then, as a sensitive for these delicate, not to say dangerous, experiments, he or she should be medically examined, in the interests of both the investigator and the sensitive, and should their health prove to be in any way below par, they should not be permitted to take part in the experiment until their health is fully restored.
I have been permitted to examine the sensitive at the moment when an entity, clad in a fully-formed temporary body, was walking amongst the experimenters; and the distorted features, the shrivelled-up limbs and contorted trunk of the sensitive at that moment proclaimed the danger connected with the production of this special form of phenomena far louder than any words of mine could do.
Needless to say, sensitives for materializations are extremely rare, not more than two or three being found to-day amidst the teeming millions who inhabit the British Islands; although a few are to be found on the European continent, and several in North America, where the climatic conditions are said to be more favorable for the development of such persons.