They are but windows at the best, mere holes in a dead wall, disconnected, perched aloft; they are not hinged doors opening straight upon life.

But they have this mark of their own that at each of them stands a figure with a pair of eyes, or at least with a field-glass, which forms, again and again, for observation, a unique instrument, insuring to the person making use of it an impression distinct from every other.

He and his neighbours are watching the same show, but one seeing more where the other sees less, one seeing black where the other sees white, one seeing big where the other sees small, one seeing coarse where the other sees fine.

And so on, and so on; there is fortunately no saying on what, for the particular pair of eyes, the window may NOT open; "fortunately" by reason, precisely, of this incalculability of range.

The spreading field, the human scene, is the "choice of subject"; the pierced aperture, either broad or balconied or slit-like and low-browed, is the "literary form"; but they are, singly or together, as nothing without the posted presence of the watcher--without, in other words, the consciousness of the artist.