Familiar spirits of this class are not always invisible; and they can assume such forms as may be necessary to serve their purposes. A favourite shape with them is that of a young and lovely woman. Comparisons are here suggested with the water-maidens, and other like forms of this fancy; but they need not be pursued. It is necessary for the student of phantoms to constantly remind himself of the omnipresent danger of being enticed too far afield, unless he keep somewhat sternly to the path he has marked out. How ancient is the notion of a familiar spirit in female form, may be seen from accounts which are given by Giraldus and other old writers. Near Caerleon, (Monmouthshire,) in the twelfth century, Giraldus tells us[80] there lived 'a Welshman named Melerius, who by the following means acquired the knowledge of future events and the occult sciences: Having on a certain night met a damsel whom he loved, in a pleasant and convenient place, while he was indulging in her embraces, instead of a beautiful girl he found in his arms a hairy, rough and hideous creature, the sight of which deprived him of his senses; and after remaining many years in this condition he was restored to health in the church of St. David's, through the merits of its saints. But having always had an extraordinary familiarity with unclean spirits, by seeing them, knowing them, talking with them, and calling each by his proper name, he was enabled through their assistance to foretell future events; he was indeed often deceived (as they are) with respect to circumstances at a great distance; but was less mistaken in affairs which were likely to happen soon, or within the space of a year. They appeared to him on foot, equipped as hunters, with horns suspended from their necks, and truly as hunters not of animals but of souls; he particularly met them near monasteries and religious places; for where rebellion exists there is the greatest need of armies and strength. He knew when any one spoke falsely in his presence, for he saw the devil as it were leaping and exulting upon the tongue of the liar; and if he looked into a book faultily or falsely written, although wholly illiterate he would point out the place with his finger. Being questioned how he could gain such knowledge, he said he was directed by the demon's finger to the place.' In the same connection Giraldus mentions a familiar spirit which haunted Lower Gwent, 'a demon incubus, who from his love for a certain young woman, and frequenting the place where she lived, often conversed with men, and frequently discovered hidden things and future events.'