M. Viollet-le-Duc, in his "Dictionnaire Raisonné de l'Architecture," thus describes the building: "De la base au faîte, l'edifice est entièrement construit en pierre dure de choix, connue sous le nom de liais cliquart (Portland stone) chaque assise est cramponnée par des agrafes de fer coulées en plomb, les tailles et la pose sont exécutées avec une précision rare; la sculpture en est composée et ciselée avec un soin particulier. Sur aucun point on ne peut constater ces négligences qui ne sont que trop souvent le résultat de la précipitation." At page 401 of the above work is an explanation of the system of courses employed by Pierre de Montereau--a manner of strengthening masonry which was in use before this period (13th century), but which was improved upon by the great architect of the Sainte-Chapelle. It is very similar to the system now in use. The only communication between the lower and upper chapels at the present time is by means of the small turret staircase, but formerly the upper church was approached by a wide exterior flight of forty-four steps. It was reconstructed many times, and the last one, in the Egyptian style, was dated 1811. The demolition of this is no loss; but it seems a pity it should not have been replaced by one in better taste, as the only approach to the upper chapel (except the turret stairs) is through the corridors of the Palais de Justice. The first thing that strikes the visitor upon entering is the enormous size of the windows, which occupy the entire space between the buttresses, and rise to the base of the roof. All the weight of the vaulting rests, therefore, upon the exterior buttresses, but not the slightest inflection has ever taken place. The church is built truly east and west, the entrance to each chapel being by separate portals. The only modification the exterior of the building has sustained since S. Louis' time is the addition of a little oratory attributed to Louis XI., and the rebuilding of a part of the _façade_ in the 15th century.