At her entranceways Chartres set forth the calendar of months in small medallioned allegories, and here and at Amiens, Paris, and Rheims was given a complete system of moral philosophy through the contrast of virtues with vices. On the north façade of Chartres is carved "Libertas" under the image of a virtue. Bishop John of Salisbury would have approved this: "For there is nothing more glorious than freedom," he wrote, "save virtue, if indeed freedom may be rightly severed from virtue, for all who know anything know that true freedom has no other source." In structural technique the fenestration of Chartres was a stride forward, and both the cathedrals of Paris and Soissons learned immediately from its clearstory arrangement--the first attempt to fill with colored glass the entire space between the active wall shafts. "In certain parts of the cathedral of Chartres," says M. Mâle, "is a magnificent amplitude, a superabundance of power. Each of the nave's windows is surmounted by an immense rose as wide as the bay, a conception as proud as ever an architect realized. It is one of those flashes of genius such as came to Michael Angelo. Those great orbs of light, those wheels of fire that dart sparkling rays are one of the beauties of the cathedral."[111] Notre Dame has preserved over two hundred of the ancient, imaged windows. The oldest and the best are three large lancets under the western rose which, like the Royal Portal beneath them, are the work of Suger's craftsmen who came here from St. Denis. One of these noted windows relates the childhood of Christ, another His Passion and Resurrection, and the third is a tree of Jesse, similar to one in St. Denis.[112] The iron bars supporting the sheet of glass do not conform to the outline of the medallions, hence it is somewhat more difficult to decipher the scenes than in XIII-century work. None the less, these, the oldest windows of the cathedral, are the peer of any colored glass ever made, because of their inherent genius for decorative effect and their conscientious workmanship. Many a pen has tried--in vain--to describe the marvelous deep blue which blends together the other colors--the streaky ruby, the emerald green, the sea-green white, the brownish purple and pink, the yellow pot metal.