54

OF GROINED RIBBED VAULTS.

“ that the roofs were turned into arches of massystone, joined by a cement that grew harder by time ;and the building stood from century to century de-riding the solstitial l’ains, and equinoctial hurricanes,without need of reparation.” Thick stone walls willremain to mark the site of a building, but vaults alonecan preserve the building itself. It is the roof whichmakes the house.

Previously to vaulting the naves of the Cathedrals,round-headed arches were general; and there werefew examples either of rib or pannel vaulting, pointedarches, pinnacles, or buttresses. While vaults wereconfined to low buildings, as crypts and the ailes ofcathedrals, it is obvious, that the thick walls of theSaxons and Normans would be able to resist theirthrusts.

The numerous arches at the Alhambra in Granada ,at the Mosque at Cordoba , probably built about theeighth century, are elliptical horse-shoe arches.

In the vaulting of the ailes of Durham and Can-terbury Cathedrals are to be observed, the “ arcsdoubleaux,” and groined ribs in round-headed vaults.In the naves of the same buildings is the same cha-racter of vaulting, except that the arch of the vaultis pointed. Some vaults of this kind are to be dis-tinguished from others by the positing of the stonesof the vault between the ribs, which, instead of beingparallel to each side of the plan, as in Roman groinedvaults, take a mean direction between the groinedrib, and the ribs of the arches over the sides; whencethey meet the vertex at an acute angle, and are re-ceived by stones running along the vertex,_ cut in theform of a ratchet. The advantage of this method