The Church of the Ste. Trinité, on the right bank of the Maine, built by the sons or pupils of those architects who had planned St. Maurice for the hill on the opposite shore, marks a fresh advance in the construction of these vaults. Like St. Maurice, it has but a single aisle, which is divided into three bays, each as nearly as possible square on plan. The system of vaulting takes on a greater elegance by the insertion of a transverse arch, with its supporting shafts, in the centre of each bay. This divides the bay into two equal parts, and, cutting the diagonal ribs at their intersection, supports them at the critical point. Fig. 19 gives the plan of these vaults, the system of which was eagerly seized upon by the Northern architects, and the great abbey church of Noyon appears to have been the first-fruits of this new development of the Angevin idea. [Illustration: 19. PLAN OF THE CHURCH OF LA STE. TRINITÉ AT ANGERS] [Illustration: 20. LONGITUDINAL SECTION OF A BAY OF LA STE. TRINITÉ AT ANGERS] The great abbey churches and immense cathedrals which were built from the second half of the twelfth to the middle of the thirteenth century attest the importance of the development carried out at Angers by the arrangement of their own vaults in square compartments. For we now find this system adopted in the construction of the churches or cathedrals of Noyon, Laon, Notre Dame at Paris, Sens, and Bourges, to name only acknowledged masterpieces of so-called Gothic. [Illustration: 21. TRANSVERSE SECTION OF A BAY OF LA STE. TRINITÉ AT ANGERS] The influence of the cupola, which we established in our first chapter, was both direct and consecutive. It was direct in churches built with one aisle and vaulted on intersecting arches, and consecutive in the so-called Romanesque churches, which were either completed or modified on the new lines by the substitution of vaults on intersecting arches of dressed stone for timber roofs. A large number of buildings in England, Normandy, Germany, Northern Italy, Switzerland, the Rhine Provinces, and those of Northern France bear testimony of the highest interest to the transformations consequent on the invention of the groined vault and its universal application.