Whence the origin of these odd apparitions? The reply of modern science is that they were nothing more than the weird externalization of ideas latent in the minds of those perceiving them. Indeed, in the case of Mr. Turner there is absolute proof that this was the case, for that gentleman afterwards identified the phantom chandelier with one familiar to him as hanging from the ceiling of the college chapel in which he daily said prayers. Furthermore, there is proof--of which an abundance will be given in subsequent chapters--that often the ideas thus externalized relate to things once seen or heard but long since forgotten; it may be to things seen or heard in a wholly unconscious, or, rather, subconscious, way. And as with ideas of things, so with ideas of persons. In this connection, as illuminating vividly the problem of ghosts, may well be given an experience narrated to me by Doctor Morton Prince, the eminent Boston psychopathologist, or medical psychologist. A patient of his came to him one morning in a condition of extreme nervousness, declaring that the previous night she had seen a ghost. "I woke up," said she, "and saw at the foot of my bed a young woman, who gradually faded away." She maintained that at no time had she seen anybody resembling the apparition, but in the minute description she gave, Doctor Prince at once recognized a relative of his, with whom he remembered he had been talking in the hall when the patient last visited him. Saying nothing to her he quietly assembled a few photographs, and, before she departed, asked her to look them over. "Why," she said, picking one up, "here is my ghost!" "Yes," was Doctor Prince's reply, "and you saw your ghost in this house when you were here only a few days ago. I was talking to her as you came in." "But," objected the patient, "I certainly did not see her, for I noticed somebody was with you, and I purposely turned away as I passed, lest I should seem rude." "All the same," said Doctor Prince, "you saw her without being conscious of it--saw her, as it were, out of the corner of your eye. One fleeting glance would be enough to give you the memory image that you mistook for a ghost." Undoubtedly Doctor Prince was right, and undoubtedly this dual law of subconscious perception and memory is enough to account for some of the most impressive ghosts cited in this chapter. Even the strange haunting of the Petit Trianon, as experienced by Miss Morison and Miss Lamont, may be said to find its explanation here.