Bk. VI. Ch. III. VAULTS. 147 580. View of Aisle at St. George's, Windsor. sucli a vault as that of the cloisters at Gloucester (Woodcut No. 579), where a segment is used nearly equal to an equilateral spherical triangle. In this case they did not dare to employ a constructive decoration, but covered the space with circles so as to confuse and deceive the eye. At Windsor (Woodcut No. 580) the defect was obviated by using a low four-centred arch invented for the purpose, so that the outer tang-ent of the conoid was nearly flat, and the principal transverse rib was carried to the centre without being l)roken — as the others might have been had that mode of decoration been deemed expedi- ent. This may be considered the per- fection of this kind of vaulting, and is per- haps the most beau- tiful method ever in- vented. At West- minster (as shown in Woodcut No. 581) the difficulty was got over by reversing the curve by the introduction of pendants. This was a clever expedient, and produced a start- ling effect, but is so evidently a tour de force that the result is never quite satisfactory ; though on a small scale perfectly admissible. These, devices all answered perfectly so long as the space to be roofed was square, or nearly so ; but when this mode of vaulting came to be applied to the ba^L of the central nave, which were twice as long in one direction as in the other, the difficulties seejned insuper- able. By cutting off the angle as in the former instance (as at b, 581. Aisle in Henry VII. 's Chapel, Westminster.
