In the _Arabian Nights_, and in various other fairy tales, we also read of the sudden appearance and disappearance of palaces, castles, and other buildings of monumental character. This strange phenomenon has frequently been paralleled in recent times. It is a species of hallucination, induced by auto-suggestion or hetero-suggestion--that is, suggestion given to oneself, or suggestion from outsiders. Madame Blavatsky, in her _Nightmare Tales_, relates an interesting experience of this character: "A curious optical effect then occurred. The room, which had been previously partially lighted by the sunbeam, grew darker and darker as the star increased in radiance, until we found ourselves in an Egyptian gloom. The star twinkled, trembled, and turned, at first with a slow, gyratory motion, then faster and faster, increasing its circumference at every rotation until it formed a brilliant disk, and we no longer saw the dwarf, who seemed absorbed in its light.... All being now ready, the dervish, without uttering a word, or removing his gaze from the disk, stretched out a hand, and taking hold of mine he drew me to his side, and pointed to the luminous shield. Looking at the place indicated, we saw large patches appear, like those of the moon. These gradually formed themselves into figures, that began moving themselves about in higher relief than their natural colours. They neither appeared like a photograph nor an engraving, still less like the reflection of images on a mirror, but as if the disk were a cameo, and they were raised above its surface--then endowed with life and motion. To my astonishment and my friend's consternation, we recognized the bridge leading from Galata to Stamboul spanning the Golden Horn from the new to the old city. There were the people hurrying to and fro, steamers and caiques gliding on the blue Bosphorus, the many-coloured buildings, villas, palaces reflected in the water; and the whole picture illuminated by the noonday sun. It passed like a panorama, but so vivid was the impression that we could not tell whether it or ourselves were in motion. All was bustle and life, but not a sound broke the oppressive stillness. It was noiseless as a dream. It was a phantom picture.... The scene faded away, and Miss H---- placed herself in turn by the side of the dervish." We thus see that expectancy and suggestion alone may induce sufficiently abnormal mental states to ensure the occurrence of such images--especially in a mind previously wrought by imagination, superstition, love, or any emotion tending to bring about its temporary lack of balance. The visions induced would, of course, be mental, and not physical, in their character; they would nevertheless appear just as real to the onlooker.