To apply this to our main subject of _vaulting_, we at once see that, in addition to constructive advantages, the arch could now he proportioned in height to its supporting piers, and the unequal sides of the vaulted spaces could now be arched in such a manner as to satisfy the exigencies of the vaulting without the necessity of resorting to awkward contrivances; so that an accession was obtained at once of strength, beauty, and facility of application. I have called the use of diagonal ribs the _Magna Charta_ of the art of vaulting; but it must share this honour with the Pointed arch. Let us now proceed to trace the progress of the art under this double charter of liberty. The first introduction of the Pointed arch into vaulting seems to have been made without a full consciousness of its advantages, and rather with a view to strength and general beauty than to the convenience of covering irregular spaces, for in many early specimens--as originally in the Cathedral of Sens,[46] and in the work of William of Sens at Canterbury,[47]--the round arch continued to be used in the narrow bay against the walls, while the pointed arch was used for the wider spans. In nearly all English specimens, however, full advantage was at once taken of the newly-attained freedom: thus, at St. Joseph’s Chapel, at Glastonbury,--a work otherwise purely round-arched,--the groining assumes throughout the pointed form, the narrow bays being especially acute.[48] The same is the case at St. Cross, another very early transitional work,[49] and in the nave and transepts of St. David’s Cathedral[50] (erected about 1180), though the groining was never carried out, we have the preparations for it with pointed wall-ribs in the sides, while the round arch is mainly used beneath. I shall, therefore, disregard this occasional inconsistency. [Illustration: Fig. 349. A. Transverse ribs. B. Diagonal ribs. C. Wall ribs. D. Ridge ribs.] Before going further, I will, to prevent mistake, give the names of the parts of a groined compartment (Fig. 349). The main ribs from wall to wall are called by us _transverse ribs_; by the French, _arcs doubleaux_. Those which pass from angle to angle, intersecting in the middle, we call _diagonal ribs_; the French, _arcs ogives_. Those which adhere to the wall, we call _wall ribs_; the French, _formerets_. If there is a rib or moulding along the apex, we call it a _ridge rib_; the French, a _lierne_. The latter, however, does not exist in early examples. Other features appear as we proceed, but I limit my first list to the simpler forms of vaulting. The French names are found in the treatise of Philibert de l’Orme, a work of the sixteenth century; whether they have been traditionally kept up I do not know, but they are now universally adopted by French writers on the subject. I will just go over our leading cases, already treated of, showing the changes effected in them by the use of the pointed arch.