Night-time, regarded as a separate sphere of creation, is a universe in itself. The material nature of man, upon which philosophers tell us that a column of air forty-five miles in height continually presses, is wearied out at night, sinks into lassitude, lies down, and finds repose. The eyes of the flesh are closed; but in that drooping head, less inactive than is supposed, other eyes are opened. The unknown reveals itself. The shadowy existences of the invisible world become more akin to man; whether it be that there is a real communication, or whether things far off in the unfathomable abyss are mysteriously brought nearer, it seems as if the impalpable creatures inhabiting space come then to contemplate our natures, curious to comprehend the denizens of the earth. Some phantom creation ascends or descends to walk beside us in the dim twilight: some existence altogether different from our own, composed partly of human consciousness, partly of something else, quits his fellows and returns again, after presenting himself for a moment to our inward sight; and the sleeper, not wholly slumbering, nor yet entirely conscious, beholds around him strange manifestations of life--pale spectres, terrible or smiling, dismal phantoms, uncouth masks, unknown faces, hydra-headed monsters, undefined shapes, reflections of moonlight where there is no moon, vague fragments of monstrous forms. All these things which come and go in the troubled atmosphere of sleep, and to which men give the name of dreams, are, in truth, only realities invisible to those who walk about the daylight world. The dream-world is the Aquarium of Night.