themselves to the representation of what they could represent.  In the interest of truth, of reality, they narrowed the gamut of their modulations, they attempted less, upheld by the certainty of accomplishing more.  For a time French landscape was pitched in a minor key.  Suddenly Claude Monet appeared.  Impressionism, as it is now understood, and as Manet had not succeeded in popularizing it, won instant recognition.  Monet’s discovery was that light is the most important factor in the painting of out-of-doors.  He pushed up the key of landscape painting to the highest power.  He attacked the fascinating, but of course demonstrably insolvable, problem of painting sunlight, not illusorily, as Fortuny had done by relying on contrasts of light and dark correspondent in scale, but positively and realistically.  He realized as nearly as possible the effect of sunlight—­that is to say, he did as well and no better in this respect than Fortuny had done—­but he created a much greater illusion of a sunlit landscape than anyone had ever done before him, by painting those parts of his picture not in sunlight with the exact truth that in painting objects in shadow the palette can compass.

Nothing is more simple.  Take a landscape with a cloudy sky, which means diffused light in the old sense of the term, and observe the effect upon it of a sudden burst of sunlight.  What is the effect where considerable portions of the scene are suddenly thrown into marked shadow, as well as others illuminated with intense light?  Is the absolute value of the parts in shadow lowered or raised?  Raised, of course, by reflected light.  Formerly, to get the contrast between sunlight and shadow in proper scale, the painter would have painted the shadows darker than they were before the sun appeared.  Relatively they are darker, since their value, though heightened, is raised infinitely less than the value of the parts in sunlight.  Absolutely, their value is raised considerably.  If, therefore, they are painted lighter than they were before the sun appeared, they in themselves seem truer.  The part of Monet’s picture that is in shadow is measurably true, far truer than it would have been if painted under the old theory of correspondence, and had been unnaturally darkened to express the relation of contrast between shadow and sunlight.  Scale has been lost.  What has been gained?  Simply truth of impressionistic effect.  Why?  Because we know and judge and appreciate and feel the measure of truth with which objects in shadow are represented; we are insensibly more familiar with them in nature than with objects directly sun-illuminated, the value as well as the definition of which are far vaguer to us on account of their blending and infinite heightening by a luminosity absolutely overpowering.  In a word, in sunlit landscapes objects in shadow are what customarily and unconsciously we see and note and know, and the illusion is greater if the relation between them and