The wide ambulatory of Poissy is groin-vaulted, but diagonals cover the two oriented apsidioles that open on a false transept, which arrangement of pseudo-transept with chapels was copied soon after at Sens. The three easternmost bays of the nave have retained their primitive intersecting ribs, which are round-arched, decorated, and very broad, as are the transverse arches that separate the vault into sections. Poissy's sculpture is of an advanced type. Owing to later changes, there is much patchwork in the church. ST. DENIS-EN-FRANCE[31] Give all thou canst: high Heaven rejects the lore Of nicely calculated less or more: So deemed the man who fashioned for the sense These lofty pillars, spread this branching roof Self-poised. --WORDSWORTH. [Illustration: _Poissy. An Early Example of Gothic Vaulting (c. 1135)_] Finally came the hour of the new architecture's clear achievement. After all the trial efforts, there now was built, midway in the XII century, a monument which was to wield momentous influence. With the erection of St. Denis, the center of Gothic art may be said to have shifted slightly south, to Paris. From the capital the new movement spread out in systematic progression--each church comprehending better than had its predecessor the principle of thrust and counterthrust, each drawing from it further consequences. St. Denis did not put a stop abruptly to the coexistence in the same edifice of both systems of vaulting any more than it began immediately the usage of all the consequences of diagonals. Yet none the less the Royal Abbey is rightly called the first Gothic monument, since here first was demonstrated stout-heartedly the advantages of the new system. Abbot Suger was the first to employ the generating member with the full intelligence of its results. "From the moment of St. Denis' conception, Amiens had become inevitable." It was Suger who wedded definitely the pointed arch and the intersecting ribs. He dared to make piers so slender that the beholders were astonished they could carry the weight of a stone roof; he dared to open his walls by windows so large that his choir was called by the people the lantern of St. Denis. The mastery by Suger's craftsmen of the art of stained glass was to have profound consequences in Gothic structure, since it hastened the suppression of the wall screen between the active members: "Behold I will lay thy stones with fair colors, and thy foundations with sapphires; and I will make thy windows of agates, and thy gates of carbuncles, and all thy borders of pleasant stones."