Now in the working of this revolution the Van Eycks had no part whatever. They did not invent “oil painting” or anything like it. They were the greatest painter-craftsmen ever known, and they and the generations that followed them in Flanders and Italy held faithfully to the old threefold mode of operation until Tintoretto, Velasquez, and Rubens began to merge the three in one and to lay the foundations for the present lamentable subterfuges of the Salon and the Royal Academy. What they did do was this: until Hubert’s time every painter had been searching for some medium which would not mitigate the perfect transparency of their hand-ground colours and would dry quickly. All kinds of viscous things had been employed--white of egg, fig juice, and other less seemly media--but none was wholly satisfactory. Oil was the natural thing, but oil was an unconscionable time in drying. Hubert Van Eyck found some oil medium (or varnish) that dried quickly and this at once became the universal medium. It was a great discovery and a great boon, but it had nothing whatever to do with “oil painting,” which did not actually come into existence until the dark days of the late eighteenth or early nineteenth century, therefore the skirts of the Van Eycks are clear and we can absolve them of all responsibility. There never was a school of such consummate craftsmanship as this of Flanders. The Van Eycks, Memling, Van der Weyden were the most perfectly trained, the most comprehensively competent, and the most conscientiously laborious artists ever known; also they understood drawing, composition, and lighting as no others ever did, while their sense of beauty of colour, either in itself or in subtle and splendid combinations, was unique. They were not portents, sudden meteors shooting across a dark sky, they simply continued and developed a long and glorious tradition. Long before them the monasteries had been producing great art of every kind--frescos, illuminations, stained glass, embroidery, painted sculpture--and it was all art of the greatest. When Hubert painted the “Adoration of the Lamb,” he merely gathered together all these arts and manifested his enormous and astounding synthesis in concentrated form, and better than any one had ever done before. All the intricate delicacy of jewel work, all the vivacity of clean-cut sculpture, all the suavity of silken needlework, all the flaming splendour of stained glass are brought together here in one astonishing combination, and to this era-making synthesis is added the living light [Illustration: OUR LADY, FROM THE TRYPTICH AT GHENT HUBERT VAN EYCK ] and the human appeal of the poignant beauty of the world, and the transcendent magic of the supernatural, sacramentally and visibly set forth.