REFRACTION
which they carried it landed them in the quagmire of the commonplace and vulgar. Nevertheless, I am certain that no picture in its extreme corners should be painted with quite the same vigor of technique or strength of color or of value as in its natural focal centre. Indeed, a careful study of certain masterpieces shows that wonderful results have occasionally been obtained by the reserved and masterly use of this principle. In the "Shepherdess," by Millet, for instance, the sense of immensity and of limitless space which marks and distinguishes that great canvas is derived largely from the extremely subtle use to which he put his knowledge of this obscure phenomenon.
So far I have spoken of refraction only in its relation to values. But there is also color refraction; and here its action is much more in harmony with the scien-
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