To the hidden places over the vaults of Notre Dame fled the illustrious chancellor of Paris University, Gerson, to whom during two centuries was attributed the _Imitation of Christ_. In 1407 he had reprobated the murder of the Duke of Orléans (builder of Pierrefonds) by the Duke of Burgundy (of the regal Dijon tomb), and the mob rose and sacked his house. It is said that for months Gerson lay concealed in Notre Dame, alone with his books, and given over to prayer and meditation. The present stained glass in Notre Dame is modern, save for the north, south, and west rose windows, the trilogy of light usually found in big cathedrals. The roses of the transept belong to the Paris school which led in the art of glassmaking during the second half of the XIII century. So large were the spaces then to be filled that the scrupulous patience of the St. Denis craftsmen was no longer possible. Backgrounds had to be made quickly by bold, simple trellis designs, and as the most frequent background was a red trellis on a blue field, and the juxtaposition of red and blue makes violet, in too many of the windows of that period prevails a melancholy purplish hue. Originally the choir of Notre Dame boasted some glass given by Abbot Suger himself to the preceding Romanesque cathedral. In the XVIII century, those over-confident _gens de goût_, the cathedral canons, whose taste admitted only the neo-classic, substituted uncolored glass for the ancient windows. They say that when the workmen were removing Suger's priceless glass, they were dumfounded by its deep, ineffable blue.[84] Many a treasure of Notre Dame was destroyed by the Revolution, and the church itself was put up for sale and escaped demolition by merest chance. It served as Temple of Reason, as warehouse, as fête hall. Again, during the Commune, in 1871, for the purpose of destroying it, chairs were piled high in the choir and set on fire, but brave men broke in the doors and extinguished the flames. Early in the World War, in 1914, a German airship dropped a bomb on Notre Dame which pierced the roof of the transept's northern arm. THE SAINTE-CHAPELLE[85] Li cuers doit estre semblans à l'encensier, Tous clos envers la terre et overs vers le ciel. --(Old song of the Middle Ages). On the same isle in the Seine with Notre Dame stands the Sainte-Chapelle, the reliquary of stone and jeweled glass which the saint-king had made to enshrine the Crown of Thorns redeemed from Constantinople. To-day it is a body without a soul, as the revered crown is kept in the treasury of Notre Dame, and until a memorial service during the World War, Mass had not been said in the _reliquaire de souvenirs_ for fifteen years.