_The Silver Mirror_, by A. Conan Doyle, represents a man alone night after night, working with overstrained nerves on a set of books, who sees in an antique mirror a strange scene re-enacted and finds later that the glass has once belonged to Mary, Queen of Scots, and that he has seen the murder of Rizzio. Brander Matthews also has a story concerned with re-created images in an old mirror. The looking-glass in fiction seems to be not only a sort of hand conscience, as Markheim calls it, but a betrayer of secrets, a revealer of the forgotten past, a prophet of the future as well. It is also a strange symbol to show hearts as they are in reality, reflecting the soul rather than the body. It is employed in diverse ways and is an effective means of supernatural suggestion, of ghostly power. The Fourth Dimension is another motif that seems to interest the writers of recent ghostly tales. They make use of it in various ways and seem to have different ideas concerning it, but they like to play with the thought and twist it to their whim. Ambrose Bierce has a collection of stories dealing with mysterious disappearances, in which he tells of persons who are transferred from the known, calculable space to some "non-Euclidean space" where they are lost. In some strange pockets of nowhere they fall, unable to see or to be seen, to hear or to be heard, neither living nor dying, since "in that space is no power of life or of death." It is all very mysterious and uncanny. He uses the theme as the basis for a number of short stories of ghostly power, which offer no solution but leave the mystery in the air. In some of these stories Bierce represents the person as crying out, and being heard, but no help can go, because he is invisible and intangible, not knowing where he is nor what has happened to him. H. G. Wells, in _The Plattner Case_, which shows an obvious influence of Bierce, gives a similar case. He explains the extraordinary happenings by advancing the theory that Plattner has changed sides. According to mathematics, he says, we are told that the only way in which the right and left sides of a solid body can be changed is by taking that body clean out of space as we know it, out of ordinary existence, that is, and turning it somewhere outside space. Plattner has been moved out into the Fourth Dimension and been returned to the world with a curious inversion of body. He is absent from the world for nine days and has extraordinary experiences in the Other-World. This happens through an explosion in the laboratory where he is working, similarly to Wells's story of Davidson, where the infringement on the Fourth Dimension is the result of a lightning stroke.