Mr. Porter acknowledges that not a single Lombard church was rib-vaulted throughout, that the Lombard architects never counterbutted their diagonals properly, that their vaults proved unsatisfactory, so that after 1120 they returned to their groin and barrel vaulting, or used timber roofs, in those regions where wood abounded. The destruction of Milan through the German invasion, in 1162, was a fatal blow to Lombard architecture. We can only conjecture how northern Italy might have worked out the problem of stone roofs. The best definition of Gothic, thinks Mr. Porter, is Professor Moore's, which concludes thus: "Wherever is wanting a framework maintained on the principle of thrust and counterthrust, there we have not Gothic." The Lombard churches never met the vault thrust with counterthrust of buttress. Surely not in Lombardy was conceived the new system of construction? S. Ambrogio at Milan was cited as l'oeuvre initiale, till it was proved that it was built not in the IX century, but after 1067; and as later disasters necessitated reconstructions, none of the present diagonals was extant before 1198. S. Abondio at Como, consecrated by Urban II, in 1095, has some very early intersecting ribs, but they are more a step toward the new system than a true Gothic vault, since the ribs merely reinforce and do not carry the cells. M. Camille Enlart contends that the systematic use of Gothic in Italy was not earlier than the second quarter of the XIII century, and was brought across the Alps by French Cistercian monks. Though for centuries Italy used it, she apprehended its constructive principle imperfectly. Because she possessed a Niccola Pisano, a Giotto, a family of Cosmati to veil the poverty of her Gothic skeleton with details of consummate beauty, criticism is silenced. Her best Gothic monument, the cathedral of Siena, was insecure because of technical errors. Always was Italy adverse to showing the mechanism by which an edifice stood; few flying buttresses were ever built south of the Alps. She preferred the classic wide spacing of piers, an unencumbered interior, and small windows against her hot sun. Who remembers that he is in a Gothic church when in the somber cathedral of Florence? Its long nave is divided into four bays where a northern church would have used eight. For Italy the Renaissance was a whole-hearted return to a national art which she could fully understand.