This last sentence applies to the theory of _points de repère_ as well. As a general rule, the crystal vision, however meaningless and fantastic, is a thing which changes and develops somewhat as a dream does; following, it may be, some trivial chain of associations, but not maintaining, any more than a dream maintains, any continuous scheme of line or colour. At the most, the scraps of reflection in the crystal could only _start_ such a series of pictures as this. And the start, the initiation of one of these series, is often accompanied by an odd phenomenon mentioned above--a _milky clouding_ of the crystal, which obscures any fragments of reflected images, and from out of which the images of the vision gradually grow clear. I cannot explain this clouding. It occurs too often and too independently to be a mere effect of suggestion. It does not seem to depend on any optical condition--to be, for instance, a result of change of focus of the eye, or of prolonged gazing. It is a picture like other pictures; it may come when the eyes are quite fresh (nor ought they ever to be strained); and it may persist for some time, so that the scryer looks away and back again, and sees it still. It comes at the beginning of a first series of pictures, or as a kind of drop scene between one series of pictures and another. Its closest parallel, perhaps, is the mist or cloud out of which phantasmal figures, "out in the room," sometimes seem to form themselves. Moreover, the connection, if one can so call it, between the crystal and the vision is a very variable one. Sometimes the figures seem clearly defined within the crystal and limited thereby; sometimes all perception of the crystal or other speculum disappears, and the scryer seems clairvoyantly introduced into some group of life-sized figures. Nay, further, when the habit of gazing is fully acquired, some scryers can dispense with any speculum whatever, and can see pictures in mere blackness; thus approximating to the seers of "faces in the dark," or of _illusions hypnagogiques_. On the whole it seems safest to attempt at present no further explanation of crystal-gazing than to say that it is an empirical method of developing internal vision; of externalising pictures which are associated with changes in the sensorial tracts of the brain, due partly to internal stimuli, and partly to stimuli which may come from minds external to the scryer's own. The hallucinations thus induced appear to be absolutely harmless. I at least know of no kind of injury resulting from them; and I have probably heard of most of the experiments made in England, with any scientific aim or care, during the somewhat limited revival of crystal-gazing which has proceeded for the last few years.