The monks who conceived the twelfth century windows, or painted the pictures of the saints, only sought to render an emotion by a conventional symbol which should rouse a response. Consequently they used marvellous combinations of colours, in which blue was apt to predominate, and they harmonized their colours with gold. Viollet-le-Duc has elaborately explained how this was done.[400] But such a system was not pretentious, and was incompatible with perspective. The mediæval burgher, like the Roman, was rich, and wanted to appear so. He demanded more for his money than a solemn portrait of a saint. He craved a picture of himself, or of his guild, and above all he insisted on display. The fourteenth century was the period when the reds and yellows superseded the blues, and when the sense of harmony began to fail. Furthermore, the burgher was realistic and required a representation of the world he saw about him. Hence came perspective, the abandonment of gold, and the final degradation of colour, which sank into a lost art. For hundreds of years it has been impossible to imitate the work of the monks of Saint Denis. In Italy, the economic phenomena were yet more striking; for Italy, even in the Middle Ages, was always a commercial community, which looked on art with the economic eye. One example will suffice,--the treatment of the dome. Placed between the masterpieces of the East and West, and having little imagination of his own, the Florentine banker conceived the idea of combining the two systems and embellishing them in a cheap and showy manner. Accordingly on Gothic arches he placed an Eastern dome, and instead of adorning his dome with mosaics, which are costly, he had his interior painted at about one-quarter of the price. The substitution of the fresco for the mosaic is one of the most typical devices of modern times. Before the opening of the economic age, when the imagination glowed with all the passion of religious enthusiasm, the monks who built the abbeys of Cluny and Saint Denis took no thought of money, for it regarded them not. Sheltered by their convents, their livelihood was assured; their bread and their robe were safe; they pandered to no market, for they cared for no patron. Their art was not a chattel to be bought, but an inspired language in which they communed with God, or taught the people, and they expressed a poetry in the stones they carved which far transcended words. For these reasons Gothic architecture, in its prime, was spontaneous, elevated, dignified, and pure.