Heinrich Heine, who had a particularly nice and discriminating taste in ghosts, and who studied with such delicate pleasure the darkly woven fancies of German superstition, frankly admitted that to see his own face by moonlight in a mirror thrilled him with indefinable horror. Most of us who are blessed, or burdened, with imaginations have shared at moments in this curious fear of that smooth, shining sheet of glass, which seems to hold within itself some power mysterious and malign. By daytime it is commonplace enough, and lends itself with facile ease to the cheerful and homely nature of its surroundings. But at dusk, at night, by lamplight, or under the white, insinuating moonbeams, the mirror assumes a distinctive and uncanny character of its own. Then it is that it reflects that which we shrink from seeing. Then it is that our own eyes meet us with an unnatural stare and a piercing intelligence, as if another soul{77} were watching us from their depths with furtive, startled inquiry. Then it is that the invisible something in the room, from which the merciful dullness of mortality has hitherto saved us, may at any instant take sudden shape, and be seen, not in its own form, but reflected in the treacherous glass, which, like the treacherous water, has the power of betraying things that the air, man’s friendly element, refuses to reveal.