There are no walls; the cathedral may be said to consist of windows, rose-windows, and "stone lace-work." The strength of the whole structure depends upon a series of pillars and arches which, according to the principles of Gothic construction, ensure equilibrium, by dividing the pressures and opposing conflicting stresses. The triforium has lost that importance which it had in the early Gothic edifices. Here it is a narrow gallery running right round the church. In the nave it comprises, at each bay, two wide arches divided by two slender columns. The windows are 52 feet high and of the same width as the arcades on the ground floor. The original stained glass no longer exists. According to the canons of Gothic art, all ornamental carving must be inspired by Nature. The typical ornamentation for capitals is the crocket, intermingled here and there with other kinds of foliage. The belt of foliage below the triforium represents plants grown exclusively in Picardy, and is very finely executed. At the entrance to the nave, with its back to the first pillar on the right, is the early 16th century tomb of Canon Pierre Burry (1 _on plan_). It is a fine, expressive statue of the canon kneeling, presented by his Patron Saint, St. Peter, to an "Ecce Homo" of little note. [Illustration: TOMB OF EVRARD DE FOUILLOY. (2 _on plan_).] On each side of the great nave, below the longitudinal arcades and between the second and third pillars, are two bronze tombs supported by lions. These are the tombs of the two bishops who founded the Cathedral, and who are represented on large rectangular tablets, wearing chasuble and mitre. Beautifully executed, they are practically the only remaining specimens in France of early funeral sculpture. _To the left_, is the tomb of Geoffroy d'Eu, deceased in 1230 (3 _on plan_). _To the right_ (2 _on plan_): that of Evrard de Fouilloy, who died in 1222 (_photo opposite_). The pulpit of painted and gilded wood belongs to the end of the 18th century. It backs up against one of the northern pillars and is carried by three tall statues representing the virtues: Faith, Hope, and Charity. The Aisles The aisles are extremely lofty, the keystones of the vaults being richly sculptured. Chapels added in the 14th century terminate the aisles. Nearly all contain works of art by a local sculptor very well known in Picardy: _Nicolas Blasset_ (1600-1659). The following are of especial interest: I. =South Aisle:= Third chapel (Annunciation--_D1 on plan_); on the altar, bas-relief by _Blasset_, representing _The Annunciation_; Fourth chapel (Assumption--_D2 on plan_); on the altar, fine Virgin by _Blasset_ (_The Assumption_). II. =North Aisle:= Second chapel (Our Lady of Help--_D3 on plan_); on the altar screen, _Virgin and child trampling on serpent representing Death_ (_Blasset_); Third chapel (St. Saviour's--_D4 on plan_): _tall Byzantine Christ_ of wood known as "St. Saviour";