=The Windows= of Notre Dame are on the vast scale which is usual in the greater Gothic churches of the Ile-de-France, and present a very remarkable contrast to the small and simple windows which were deemed sufficient by the builders of our own early cathedrals in the pointed style. At Notre Dame the area of solid wall is slight in relation to the area filled in with glass. It is not so much a case of windows in walls, as of walls connecting windows. The external buttress system and the internal vaulting system at Notre Dame comprise the essentials of the structure, so that the walls are of the nature of enclosures rather than necessary structural parts. We have travelled far from the Romanesque principle, in which the walls were primarily weight-bearers. The windows of the aisles and of the ambulatory are of great size and display many differences of detail, but they nevertheless maintain a general similarity, the designers, while appreciating the value of uniformity, being too richly endowed with the prevailing fertility of invention in matters of decorative detail exactly to repeat even the most successful arrangement. Each is divided into two main pointed lights, above which a large circle, quatrefoil or similar device, occupies the head of the window, the arches also being cusped or foiled in varying patterns. The main lights are again subdivided into two, with trefoils or quatrefoils in the heads. [Illustration: _Photo_] [_Ed. Hautecœur, Paris._ TRIFORIUM WINDOWS.] Above these noble windows are gabled heads whose sides are enriched with crockets or cusps, their centres being occupied with circular decorative panels, and their angles having small richly carved bosses. Sometimes the canopies consist of beautiful open-work. Everywhere grotesque gargoyles project between them, and the mouldings terminate in corbels in the shape of small, highly wrought human heads. This series of windows emphasises the prodigality with which sculpture in human forms or in the forms of naturalistic or fantastic animals is to be found in nearly all parts of Notre Dame. It is this prodigality, wisely distributed, which places this cathedral in such acute contrast--speaking from the standpoint of the uninitiated observer--to our own early pointed structures. The upper aisle-wall between the lower tier of flying buttresses is in some parts of the building occupied by wheel windows of varied pattern, most elaborately ornamented. But at the east end the triforium lights show another device: two small arches have in the angle between them quatrefoiled openings. It is notable that this dignified and beautiful device is foreshadowed by some of the windows in the Byzantine church in Athens, and even in the sixth-century church of Qualb Louzeh, in Central Syria.