Toward the beginning of the thirteenth century, the architect of the Cathedral of Chartres sought out entirely new window combinations to light the nave from above.  Below, in the side aisles he kept to the customs of the times; that is, he opened pointed windows which did not wholly fill the spaces between the piers; he wanted, or was willing to leave here below, the effect of a wall.  But in the upper part of his building we see that he changed the system; he throws a round arch directly across from one pier to the next; then, in the enormous space which remains within each span, he inserts two large pointed windows surmounted by a great rose ...  We recognize in this construction of Notre Dame de Chartres a boldness, a force, which contrast with the fumbling of the architects in the Ile de France and Champagne.  For the first time one sees at Chartres the builder deal frankly with the clerestory, or upper fenestration, occupying the whole width of the arches, and taking the arch of the vault as the arch of the window.  Simplicity of construction, beauty in form, strong workmanship, structure true and solid, judicious choice of material, all the characteristics of good work, unite in this magnificent specimen of architecture at the beginning of the thirteenth century.

Viollet-le-Duc does not call attention to a score of other matters which the architect must have had in his mind, such as the distribution of light, and the relations of one arrangement with another:  the nave with the aisles, and both with the transepts, and all with the choir.  Following him, we must take the choir separately, and the aisles and chapels of the apse also.  One cannot hope to understand all the experiments and refinements of the artist, either in their successes or their failures, but, with diffidence, one may ask one’s self whether the beauty of the arrangement, as compared with the original arrangement in Paris, did not consist in retaining the rose-motive throughout, while throwing the whole upper wall into window.  Triumphant as the clerestory windows are, they owe their charm largely to their roses, as you see by looking at the same scheme applied on a larger scale on the transept fronts; and then, by taking stand under the croisee, and looking at all in succession as a whole.

The rose window was not Gothic but Romanesque, and needed a great deal of coaxing to feel at home within the pointed arch.  At first, the architects felt the awkwardness so strongly that they avoided it wherever they could.  In the beautiful facade of Laon, one of the chief beauties is the setting of the rose under a deep round arch.  The western roses of Mantes and Paris are treated in the same way, although a captious critic might complain that their treatment is not so effective or so logical.  Rheims boldly imprisoned the roses within the pointed arch; but Amiens, toward 1240, took refuge in the same square exterior setting that was preferred, in 1200, here