250 COMPARATIVE ARCHITECTURE. (tiercerons), ridge ribs, and a new set of ribs known as Lierne ribs, from the French lien — to bind or hold. The name " lierne " is applied to any rib, except a ridge rib, not springing from an abacus. In the early plain-ribbed vaulting each rib marked a groin, i.e., a change in the direction of the vaulting surface, but lierne ribs were merely ribs lying in a vaulting surface, their form being determined independently of such surface, which, however, regulated their curvature. These Hemes, by their number and disposition, often give an elaborate or intricate appearance to a really simple vault (No. 112 N, o, p, q), and in consequence of the star-shaped pattern produced by the plan of such vaults, it is often called " Stellar " vaulting (No. 112 q). Examples of this type exists in the choirs of Gloucester (a.d. 1337-1377), Wells, Ely (No. 137 f), Tewkesbury Abbey nave, Bristol (No. 112 n, o), and the vaulting of Winchester Cathedral (No. 124 e, f), as carried out (a.d. 1390) by William of Wykeham. The vaulting of this period therefore consisted of transverse, diagonal, intermediate, ridge and lierne ribs — in fact, a vault of numerous ribs, and of panels which became smaller and smaller until a single stone frequently spanned the space from rib to rib, known as " rib and panel " vaulting, Perpendicular (Fifteenth Century). — The complicated "stellar " vaulting of the late fourteenth and early fifteenth centuries (No. 112 p, q) led, by a succession of trials and phases, to a peculiarly English type of vaulting in this century known as /««, palm or comidal vaulting, in which the main ribs, forming equal angles with each other and being all the same curvature, are formed on the surface of an inverted concave cone, and connected at different heights by horizontal lierne ribs. The development was somewhat as follows : — In the thirteenth century the form of an inverted four-sided hollow rectangular pyramid was the shape given to the vault. In the fourteenth century the masons converted this shape, by the introduction of more ribs, into a polygonal (hexagonal) pyramid, as in S. Sepulchre, Holborn, and elsewhere. In the fifteenth century the setting out of the vault was much simplified by the introduction of what is generally known as " Fan " vaulting, described above (No. 112 R, s). Owing to the reduction of the size of panels, due to the increase in the number of the ribs, a return was made to the Roman method of vault construction, for in fan vaulting the whole vault was often constructed in jointed masonry, the panels being sunk in the soffit of the stone forming the vault instead of being separate stones resting on the backs of the ribs. The solid method seems to have been adopted first in the crown of the vaults where the ribs were most numerous. In some " perpendicular " aults the two
