Then increased the murmuring louder in its hoarseness with the sound of many feet trampling, and as we looked towards the North Bridge, where the lamp-lights showed faintly, the yellow glare of the advancing torches gilded the sides of the opposite shops, while the houses on this side became more jetty in their intervening blackness, and in another moment they were blazing over the parapet of the bridge with a motion like the walking of a centipede of fire; and so on, with the slow appearance which distance always gives to all rapid motion, the procession crossed the bridge, hiding behind the shops and houses between the bridge and Princes Street, reappearing again by the Post Office, gliding along to Calton Hill; then they paused for a moment, turned round and came towards us, foreshortened, but growing vaster as they neared, until, with a sudden burst, they were rolling along beneath us, a heaving mass of upturned faces, crimson-tinted, with a river of yellow light rolling along the centre, white flames with orange terminations and wreaths of blurring rose and purple smoke, coats reversed, shirt sleeves or bare arms waving about the torch-sticks, smut-grimed faces, more like sweeps than students, with here and there a colossal blue-vestured guardian angel of order bestriding an exaggerated horse. This is how it appeared to me and how I treated my picture--as I conceived it ought to be treated; not as I knew the men and horses to be, men and horses, but like the perturbed legions of spectres they for the moment became: ghosts of giants and dwarfs, and other strange forms, like those extinct monsters of the past, all whirling madly past me, a vision of passion and flame crossing a chaos of darkness; an invasion of demons, unreal, yet fascinating--a nightmare of glittering phantasmagoria of light and shadow, blending colour with intense blackness. In this illustration I have given you the two most direct specimens of lighting a picture that I can think of; in the one portion you have the light coming from behind and making the objects stand out dark, as in sunrises, sunsets, moonlights, or artificial lights behind figures; in the other portion you have the light thrown into the picture, as from the spectator, or in open daylight, sunshine, or lamp-light effects, when the light is in front, and shadows fall behind or from the side. I have divided both effects, as equally as they can be divided, into light and shadow, the light occupying an equal space with the dark. These are by no means the most satisfactory methods of dividing a picture, as they are apt to be mannered and fixed; what I would rather advise is, to allow either shadow or light to predominate--shadow, if force is required; light, if air and delicacy are the aims you wish to strive for. Yet, as they contain within them the primal divisions of all lighting, they are the most appropriate for my present purpose.