have evidence of the use of crystal balls as means of divination in medieval times, and
	"scrying" in some of its many forms was by no means" rare in the Greek and Roman periods. The essential ' requisite for the exercise of this species of divination is a polished surface of some sort upon which the scryer shall gaze intently ; for this purpose mirrors, globules of lead or quicksilver, polished steel, the surface of water, and even pools of ink, have been employed and have been found to > insure quite as satisfactory results as the crystal ball. The points of light reflected from the polished surface (points de repère) serve to attract the attention of the gazer and to fix the eye until, gradually, the optic nerve becomes so.fatigued that it finally ceases to transmit to the sen-sorium the impression made from without and begins to respond to the reflex action proceeding· from the brain of the gazer. In this way the impression received from within is apparently projected and seems to come from, without. It is easy to understand that the results must vary according to the idiosyncrasy of the various scryers ; for everything depends upon the sensitiveness of the optic nerve. In many cases the effect of prolonged gaz­ing upon the brilliant surface will simply produce a loss of sight, the optic nerve will be temporarily paralyzed and will as little respond to stimulation from within as from without; in other cases, however, the nerve will be only deadened as regards external impressions, while retaining sufficient activity to react against a stimulus 176