This is an economical problem which belongs to experts, but the historical value of these early evidences is still something,-- perhaps still as much as ten sous. All the windows tend to the same conclusion. Even the last pair, numbers 41 and 42, offer three personal clues which lead to the same result:--the arms of Bouchard de Marly who died in 1226, almost at the same time as Louis VIII; a certain Colinus or Colin, "de camera Regis," who was alive in 1225; and Robert of Beaumont in the rose, who seems to be a Beaumont of Le Perche, of whom little or nothing is as yet certainly known. As a general rule, there are two series of windows, one figuring the companions or followers of Louis VIII (1215-26); the other, friends or companions of Saint Louis (1226-70), Queen Blanche uniting both. What helps to hold the sequences in a certain order, is that the choir was complete, and services regularly resumed there, in 1210, while in 1220 the transept and nave were finished and vaulted. For the apside windows, therefore, we will assume, subject to correction, a date from 1200 to 1225 for their design and workmanship; for the transept, 1220 to 1236; and for the nave a general tendency to the actual reign of Saint Louis from 1236 to 1270. Since there is a deal of later glass scattered everywhere among the earlier, the margin of error is great; but by keeping the reign of Louis VIII and its personages distinct from that of Louis IX and his generation, we can be fairly sure of our main facts. Meanwhile the Sainte Chapelle in Paris, wholly built and completed between 1240 and 1248, offers a standard of comparison for the legendary windows. The choir of Chartres is as long as the nave, and much broader, besides that the apse was planned with seven circular projections which greatly increased the window space, so that the guidebook reckons thirty-seven windows. A number of these are grisailles, and the true amateur of glass considers the grisailles to be as well worth study as the legendary windows. They are a decoration which has no particular concern with churches, and no distinct religious meaning, but, it seems, a religious value which Viollet-le-Duc is at some trouble to explain; and, since his explanation is not very technical, we can look at it, before looking at the legends:--