+FAN-VAULTING.+ The next step in the process may be observed in the vaults of the choir of Oxford Cathedral (Christ Church), of the retro-choir of Peterborough, of the cloisters of Gloucester, and many other examples. The diverging ribs being made of uniform curvature, the _severeys_ (the inverted pyramidal vaulting-masses springing from each support) became a species of concave conoids, meeting at the ridge in such a way as to leave a series of flat lozenge-shaped spaces at the summit of the vault (Fig. 136). The ribs were multiplied indefinitely, and losing thus in individual and structural importance became a mere decorative pattern of tracery on the severeys. To conceal the awkward flat lozenges at the ridge, elaborate panelling was resorted to; or, in some cases, long stone pendents were inserted at those points--a device highly decorative but wholly unconstructive. At Cambridge, in +King’s College Chapel+, at Windsor, in +St. George’s Chapel+, and in the +Chapel of Henry VII.+ at Westminster, this sort of vaulting received its most elaborate development. The _fan-vault_, as it is called, illustrates the logical evolution of a decorative element from a structural starting--point, leading to results far removed from the original conception. Rich and sumptuous as are these ceilings, they are with all their ornament less satisfactory than the ribbed vaults of the preceding period. [Illustration: FIG. 131.--VAULT OF CHAPTER-HOUSE, WELLS.] +CHAPTER-HOUSES.+ One of the most beautiful forms of ribbed vaulting was developed in the polygonal halls erected for the deliberations of the cathedral chapters of Lincoln (1225), Westminster (1250), Salisbury (1250), and Wells (1292), in which the vault-ribs radiated from a central column to the sides and angles of the polygon (Fig. 131). If these vaults were less majestic than domes of the same diameter, they were far more decorative and picturesque, while the chapter-houses themselves were the most original and striking products of English Gothic art. Every feature was designed with strict regard for the structural system determined by the admirable vaulting, and the Sainte Chapelle was not more logical in its exemplification of Gothic principles. To the four above-mentioned examples should be added that of York (1280-1330), which differs from them in having no central column: by some critics it is esteemed the finest of them all. Its ceiling is a Gothic dome, 57 feet in diameter, but unfortunately executed in wood. Its geometrical window-tracery and richly canopied stalls are admirable.