LANDSCAPE PAINTING
affect only a very limited number of the sensitive nerves of the retina, you will understand that the force of their impact must be proportionately less than those which come to the eye from the full centre of vision; and if you are willing to try the experiment of looking for five minutes at a given scene in nature, keeping the gaze fixed during all that time on some focal point—a church steeple, for instance—but throwing the mind's eye constantly back and forth from outside margin to centre and from centre to outside margin again, it will gradually dawn upon you that there is an actual and very marked visual difference in the color and value intensity of the two radii. I am sure, therefore, that the eighteenth-century artists who made use of this law in their work were fundamentally correct in their intuitions; but the excess to
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