Somewhere at hand a citizen was being beaten, for vague, quick-moving forms emerged into the radiance of his lanthorn out of the deep violet of the night air.

These relations and combinations of lines and colours, these aesthetically moving forms, I call "Significant form"; and "Significant form" is the one quality common to all works of visual art.

With a little help from this carbonic acid, moving water forms most of the world's limestone caves.