Their skies are no longer golden, but blue, and flecked with cloudlets and alive with birds; wood and meadow shine in sappy green; fantastic rocks lie about, and the plains are bounded by low hills. They are drinking deep draughts from a newly-opened spring, and they can scarcely have enough of it. They would like to paint all the leaves and fruit on the trees, all the flowers on the grass, even all the dewdrops. The effect of distance too has been discovered, for there are blue hill-tops beyond the nearer green ones, and a foreground scene opens back on a distant plain (in the Ghent altar-piece, the scene with the pilgrims); but they still possess very few tones, and their overcrowded detail is almost all, from foreground to furthest distance, painted in the same luminous strong dark-green, as if in insatiable delight at the beauty of their own colour. The progress made by Jan van Eyck in landscape was immense. To the old masters Nature had been an unintelligible chaos of detail, but beauty, through ecclesiastical tradition, an abstract attribute of the Holy Family and the Saints, and they had used their best powers of imagination in accordance with this view. Hence they placed the Madonna upon a background of one colour, generally gilded. But now the great discovery was made that Nature was a distinct entity, a revelation and reflection of the divine in herself. And Jan van Eyck introduced a great variety of landscapes behind his Madonnas. One looks, for instance, through an open window to a wide stretch of country with fields and fortresses, and towns with streets full of people, all backed by mountains. And whether the scene itself, or only its background, lies in the open, the landscape is of the widest, enlivened by countless forms and adorned by splendid buildings. Molanus, the savant of Löwen, proclaimed Dierick Bouts, born like his predecessor Ouwater at Haarlem, to be the inventor of landscape painting (claruit inventor in describendo rare); but the van Eycks were certainly before him, though he increased the significance of landscape painting and shewed knowledge of aerial perspective and gradations of tone. Landscape was a distinct entity to him, and could excite the mood that suited his subject, as, for instance, in the side picture of the Last Supper, where the foreground is drawn with such exactness that every plant and even the tiny creatures crawling on the grass can be identified. The scenery of Roger van der Weyden of Brabant--river valleys surrounded by jagged rocks and mountains, isolated trees, and meadows bright with sappy green--is clearly the result of direct Nature study; it has a uniform transparent atmosphere, and a clear green shimmer lies over the foreground and gradually passes into blue haze further back.