The prevalence of a style, more or less uniform, with its main attributes harmonious and congruous, is the resultant of these forces working together. The completion of the Cathedral was carried out about 1240, and in 1250 were added the two porches at the entrance to the transepts. The sacristy was built in the thirteenth century, and a century later the little chapel of Saint Piat was attached to the eastern apse. The shortness of the nave is attributed to the desire to utilise the foundations of the old crypt for the choir and not to extend the building farther westward than the two existing towers. Between these two points, the walls of the crypt and the western towers, the nave had to be constructed and without any possibility of further extension. [Illustration: CHARTRES] No less than nine spires were originally designed and their towers actually commenced. What a magnificent effect would have been produced had they been completed! Standing on the high ground of the city, Chartres with its clustering pinnacles would have been one of the wonders of Christendom. The magnificent glass of the thirteenth century is so deep in tone that upon entering the building one is conscious of a darkness that can almost be felt, so much at variance with the effect of the interior of most large French Cathedrals. The two porches placed outside the transept doors are the subject of a panegyric from the pen of Viollet-le-Duc. He considers them as the most beautiful and harmonious additions ever made to an existing building, and their architects proved themselves to be artists of the very first rank. No more beautiful specimen of a portal of the thirteenth century can elsewhere be found to exist; glorious and rejoicing in colour and in gold, and of surpassing sculpture and full of impressive and solemn statuary. [Illustration: RUE DE LA PORTE GUILLAUME, CHARTRES]