It is to be noted in this connection that geographically the centre of things had somewhat shifted. With the loss of Spain and of Northern Africa, the Mohammedan raiding of Southern Italy and the islands, the Mediterranean was no longer a vehicle of Western civilization, but the frontier of it. Rome itself might now be regarded as a frontier town. The eruption of the barbarians from the East along the Danube had singularly cut off the Latin West from Constantinople and from all the high culture of its Empire. Therefore, the centre of that which resisted in the West, the geographical nucleus of the island of Christendom, which was besieged all round, was France, and in particular Northern France. Northern Italy, the Germanies, the Pyrenees and the upper valley of the Ebro were essentially the marches of Gaul. Gaul was to preserve all that could be preserved of the material side of Europe, and also of the European spirit. And therefore the New World, when it arose, with its Gothic Architecture, its Parliaments, its Universities, and, in general, its spring of the Middle Ages, was to be a Gallic thing. The fourth characteristic of the Dark Ages was a material one, and was that which would strike our eyes most immediately if we could transfer ourselves in time, and enjoy a physical impression of that world. This characteristic was derived from what I have just been saying. It was the material counterpart of the moral immobility or steadfastness of the time. It was this: that the external forms of things stood quite unchanged. The semi-circular arch, the short, stout pillar, occasionally (but rarely) the dome: these were everywhere the mark of architecture. There was no change nor any attempt at change. The arts were saved but not increased, and the whole of the work that men did with their hands stood fast in mere tradition. No new town arises. If one is mentioned (Oxford, for instance) for the first time in the Dark Ages, whether in Britain or in Gaul, one may fairly presume a Roman origin for it, even though there be no actual mention of it handed down from Roman times. No new roads were laid. The old Roman military system of highways was kept up and repaired, though kept up and repaired with a declining vigor. The wheel of European life had settled to one slow rate of turning. Not only were all these forms enduring, they were also few and simple. One type of public building and of church, one type of writing, everywhere recognizable, one type of agriculture, with very few products to differentiate it, alone remained. The fifth characteristic of the Dark Ages is one apparently, but only apparently, contradictory of that immobile and fundamental character which I have just been describing. It is this: the Dark Ages were the point during which there very gradually germinated and came into outward existence things which still remain among us and help to differentiate our Christendom from the past of classical antiquity.