Page:Landscape Painting by Birge Harrison.djvu/80

LANDSCAPE PAINTING microscope, and the various other scientific instruments. As we are now provided, nature is infinitely beautiful to us; while it might have been a hideous nightmare of sharp and cutting angles or edges, without rest or relief anywhere. It is not necessary for our purposes to enter here into the physiological structure of the human eye. It will be enough to state that its radius of exact vision is extremely limited; so limited in fact that at a distance of six feet from the eye it would hardly be possible for any human being to enumerate accurately the spots on a target four feet in diameter, while holding the gaze rigidly fixed on the bull's-eye. Beyond the radius of twelve inches from the centre the image begins to blur, and this blur increases rapidly, until out of the tail of the eye on either side we get only an [50]