Now, what are the elements with which our Sub-Consciousness works?--what does this ocean contain? It would be easier to discover what it does not contain. Wrecks and argosies and dead faces, mermaidens and subterranean palaces, and the traces of vanished generations; these are but a millionth part of its treasures: the Sub-Consciousness were perhaps better likened to the property-room and scene-dock of the Great Cosmic Theatre, holding infinite wardrobes and scenes ready-painted, parks and seas and libraries, and ruined cottages and whitewashed attics, to say naught of an army of supers ready to put on all the faces we have ever seen. In our Sub-Consciousness, moreover, are stored up all the voices and sounds and scents we have ever perceived, and to all these reminiscences of our own sensations are perhaps added the shadows of our ancestors' sensations--episodes that perchance we re-experience only in dreamland--so that part of the vivid vision of genius, of the poet's eye bodying forth the shapes of things unknown, may be inherited Memory. And thus Imagination, when it is not a mere fresh combination of elements experienced, may be only a peculiar variety of atavism. From this boundless reservoir, then, which holds our heredity and our experience, go forth the battalions of dreams--the infinitely possible permutations and combinations of its elements, wrought by the Working Sub-Consciousness when the poor Working Consciousness cannot get sound asleep, but must watch perforce with half an eye the procession of thoughts and images over which it has lost control. For it is the duty of Consciousness to control the stream sent up by Sub-Consciousness. When it is awake but unable to do this, we have Insanity; when asleep, Dreams. In Somnambulism the Working Sub-Consciousness is seen in an accentuated phase. It does all the work of its little brother, even to exercising its owner's muscles. To be "possessed" by a popular song is a species of insanity--Consciousness ridden by a singing Sub-Consciousness. Between our Consciousness and our Sub-Consciousness there is more or less easy communication. It is not perfect. You cannot draw up what you will from the ocean: you cannot always directly remember a name or a date that you know--you can only set an indirect train of thought at work. _Per contra_, it is not easy to transfer certain conscious states to the storehouse of Sub-Consciousness--to learn a page of prose, or deposit the memory of a piece of music, which you are forced to play slowly and thoughtfully before the digital dexterity is added to the treasures of your Sub-Consciousness. Under exceptional conditions, exceptional flotsam and jetsam is tossed up into Consciousness, as in the case of that servant girl who spoke Latin, Greek, and Hebrew in her delirium, having unconsciously absorbed the same from overhearing the studies of her learned master many years before.