There is a progressive enlarging of the bays of the choir from its entrance to its end, done too regularly to have been accidental. Professor Goodyear has developed the thesis of these intentional refinements in Gothic monuments.[166] Mr. Arthur Kingsley Porter thinks that undoubtedly there are cases when it was done with subtle design, but more often the irregularities resulted from the sound artistic taste of the old masters who preferred a free-hand drawing to mechanical perfection. "There is no excellent beauty that hath not some strangeness in the proportion," said Bacon. Some think that at Le Mans the desire was to counteract the perspective narrowing. Others say that the builder thought thus to conform the wide choir to the ancient nave of lesser breadth. Not till the day of Rayonnant Gothic was Le Mans' transept begun, and it proved exceptional in continuing building while the foreign wars ravaged France; the chapter taxed itself heavily to meet expenses. As the XIV century closed, the southern arm was finished; it is entirely blocked by the ancient tower, to which were then added two stories. Midway in the vertical wall of the northern arm (begun in 1403) appears Flamboyant tracery. As cracks soon showed, the chapter called in a new architect, Jean de Dammartin, whose grandfather and great-uncle had beautified Dijon, Bourges, and Poitiers. When in 1430 the English captured Le Mans, he passed to Tours, on whose west façade he worked. Because the Gothic transept of Le Mans was confined to the same space as the Romanesque one it replaced, it may seem too narrow for such tremendous height. It is a monument as stately and cold as the glass it frames. Window over window rises the fragile audacious sweep of color that closes the transept's northern vista, each part being bound by stone traceries into the monumental whole. White and the yellow produced by silver-stain is the general theme, with brilliant touches of green, flashed ruby, violet, and blue. It has been said that what XV-century glass needs, to give it character, are the strong black cross-hatchings of the earlier schools. In the row of lights below the big rose, a damasked background to the figures was used with good effect. Among those represented are good King René, faithful amateur of art, and his mother, Yolande of Aragon, the regent dowager of Maine and Anjou. Her son-in-law Charles VII contributed toward the transept of Le Mans.