A favorite subject of mediæval art is the life of the Christian ascetic in the Desert. In these representations a human skull may generally be seen placed before the eyes of the devotee. Such an object would fix the gaze and induce the ecstasy as well as any other. The charm of this species of contemplation must have been intense, since in search of its exaltations and illuminations the very convents were deserted; and during the fourth and fifth centuries the deserts of Idumea, of Egypt, and of Pontus, swarmed with anchorites, who seemed to live only for the sake of escaping from life, and in their fasts and mortifications rivalled, if they did not for a time even surpass, the Fakirs of the East. To such an extent was this religious enthusiasm carried, that in Egypt the number of the monks was thought to equal that of the rest of the male population. Strange consideration, if it be the fact, that a few passes of a mesmeric operator should produce the same effects which these multitudes procured through toils so painful and sacrifices to themselves and to society so costly. The Egyptian method of inducing clairvoyance in boys, by causing them to gaze on a pool of ink in the palm of the hand, has already been identified with the practice of Dr. Dee, whose blank spherical mirror is now said to be in the possession and use of a distinguished modern mesmeriser. Divination by the crystal is a well-known mediæval practice; and from the accounts of it which Delrio and others have handed down it appears to have resembled, in some remarkable particulars, the method now in use among the soothsayers of Cairo. It does not appear to make any difference whether the polished object be black or white, a mirror, a solid ball, or a transparent globe containing water: the same extraordinary series of appearances is alleged to follow an earnest inspection of it. Before proceeding to Delrio’s singular corroboration of this use of the crystal, it will be well to state what is known of divination by the phial and by the mirror. Divination by the phial is technically known as _gasteromancy_. "In this kind of divination," says Peucer, "the response is given by pictures, not by sounds. They procured glass vessels of a globular shape, filled with fair water, and set round them lighted tapers; and after invoking the demon with a muttered incantation, and proposing the question, they brought forward a pure boy-child, or a pregnant woman, who, gazing intently on the glass, and searching it with their eyes, called for, and demanded, a solution of the question proposed. The devil then answered these inquiries by certain images, which, by a kind of refraction, shone from the water on the polished and mirror-like surface of the phial."