Page:Landscape Painting by Birge Harrison.djvu/32

 best to convey the impression of motion upon the rigidly quiescent surface of a canvas. This has never been accomplished, but to assert that it is impossible would be a hazardous statement. Still another problem derives from the limitations of the human eye. A good photographic lens will see every leaf upon a tree or every individual in a crowd of ten thousand people. The human eye can see at best but a dozen or two of leaves or people, the remainder producing the effect of a more or less indefinite blur. How is this blur to be rendered with just sufficient definition to produce the desired effect upon the spectator? It is quite certain that other problems will arise, problems as unsuspected to-day as was the prismatic theory of light a hundred years ago. It is impossible of course to particularize. One small discovery frequently leads to