Fragments of vaulting, bases of pillars, stones from the roof, were mixed in shapeless chaos with a quantity of architectural and sculptured motives, notably the beautiful capitals and the key-stones of the vault, mostly broken. And on this heap of ruins the roof-timbers of the framework, deprived of all support, fell by degrees in their turn. The old harmonious construction of the nave is now to be seen only in the bays nearest the transept. The Chapelle des Œuvres was struck several times. The most serious damage was caused during the first bombardments of 1914 by a shell which exploded on the roof of the gallery (_B on plan p. _18, _photo below_) which leads to the chapel. Penetrating the roof and the framework, it caused the vault to fall in, broke the arches, and shattered the stained-glass of the chapel windows. [Illustration: GALLERY GIVING ACCESS TO THE CHAPELLE DES ŒUVRES, NOV. 1918.] [Illustration: SOUTH ARM OF TRANSEPT. _See the exterior, p. _29.] South Arm of the Transept. The bombardments have spared the south arm of the transept, a marvel of grace and simplicity, built about 1175, by Bishop Nivelon of Chérisy. It is the oldest and also the least elevated portion of the cathedral. The arm of the transept ends in a semi-circle (a peculiarity which it shares with those of the old Cathedral of Noyon and numerous Rhenish churches) and is surrounded by an ambulatory. In style it differs distinctly from that of the rest of the building, and presents the distinguishing features of primitive Gothic. The triforium—which elsewhere consists only of a narrow gallery—is here double. It comprises a story of high, wide, arched tribunes, grouped three and three, surmounted by a narrow passage with graceful colonnettes. The main vault is supported by six pointed ribs which intersect in a central key-stone ornamented with six angels. The south arm of the transept is lighted by three series of windows. Small semi-circular bays are cut in the wall of the ambulatory. The galleries are lighted—except on the right, which is ornamented with rose-windows—by tierce-point windows in groups of three. There is a final row of high tierce-point windows, also in groups of three, above the triforium. Some of the capitals are masterpieces of ornamental sculpture. Their decoration consists either of the foliage characteristic of Romanesque capitals (acanthus leaves) or of projecting crockets,—one of the earliest examples of this distinctive ornament of Gothic capitals. On the east side of the south arm of the transept there is a two-storied polygonal chapel (_C on plan, p. _18) of the same period. The key-stone of the vault of the lower chapel represents two angels carrying the _Agnus Dei_ on a cloth. The upper chapel, in which the Treasure was formerly kept, communicates with the galleries. The Choir and Apse.