Chertsey and Westminster certainly, and Abingdon very probably, were destroyed, or at least sacked, in the Danish invasions, but their roots lay too deep to allow them to disappear: they re-arose, and a generation before the Conquest were again by far the principal centres of production and government in the Thames Valley. Indeed, with the exception of the string of royal estates upon the banks of the river, and of the town of Oxford, Chertsey, Westminster and Abingdon were the only considerable seats of regulation and government upon the Thames, when the Conquest came to reorganise the whole of English life. With that revolution it was evident that a great extension not only of the numbers, but especially of the organisation and power, of the monastic system would appear: that gaps left uninfluenced by it in the line of the Thames would be filled up, and all the old foundations themselves would be reconstructed and become new things. The Conquest is in its way almost as sharp a division in the history of England as is the landing of St Augustine. In some externals it made an even greater difference to this island than did the advent of the Roman Missionaries, though of course, in the fundamental things upon which the national life is built, the re-entry of England into European civilisation in the seventh century must count as a far greater and more decisive event than its first experience of united and regular government under the Normans in the eleventh. Moreover although the Conquest largely changed the language of the island, introduced a conception of law in civil affairs with which the Anglo-Saxon aristocracy were quite unfamiliar, and began to flood England with a Gallic admixture which flowed .uninterruptedly for three hundred years, yet it did not change the intimate philosophy of the people, and it is only the change of the intimate philosophy of a people which can have a revolutionary consequence. The Conquest found England Catholic, vaguely feudal, and, though in rather an isolated way, thoroughly European. The Normans organised that feudality, extirpated whatever was unorthodox, or slack in the machinery of the religious system, and let in the full light of European civilisation through a wide-open door, which had hitherto been half-closed. The effect, therefore, of the Conquest was exercised upon the visible and mutable things of the country rather than upon the nourishing inward things: but it was very great, and in nothing was it greater than in its inception of new buildings and the use everywhere of stone. Under the Normans very nearly all the great religious foundations of England re-arose, and that within a generation. New houses also arose, and the mark of that time (which was a second spring throughout Europe: full of the spirit of the Crusades, and a complete regeneration of social life) was the rigour of new religious orders, and especially the transformation of the old Benedictine monotony.