In times before the Roman legionaries planted their firm feet in Britain, there was a very formidable fortress at Cambridge. It contained about sixty acres; it was surmounted by one of those mighty earthworks which the hand of man in the old days raised by sheer brute force, or rather by enormous triumph of organized labour. The Romans drove out the Britons, and settled a garrison in the place. Two of the great Roman roads intersected at this point, and the conquerors called it by a new name, as was their wont, retaining some portion of the old one. In their language it was known as _Caniboritum_. The primeval fortress stood on the left bank of the river, which some called the Granta and some called the Cam; and for reasons best known to themselves, the Romans did not think fit to span that river by a bridge, but they made their great Via Devana pass sheer through the river-as some Dutch or German Irrationalist has pretended that the children of Israel did when they found the Jordan barring their progress--that is, those Roman creatures constructed a solid pavement in the bed of the sluggish stream, over which less audacious engineers would have thrown an arch. Through the water they carried a kind of causeway, and the name of the place for centuries indicated that it was situated on the _ford_ of the Cam. But what the Roman did not choose to do, that the people that came after him found it needful to do. In the Saxon Chronicle we find that the old fortress which the Romans had held and strengthened, and then perforce abandoned, had got to be called Granta-brygge; and this name, or something very like it, it retained when the great survey was made as the Norman Conqueror's reign was drawing to its close. By this time the town had moved across to the right bank of the river, and had become a town surrounded by a ditch and defended by walls and gates. Already it contained at least four hundred houses, and on the site of the old mound the Norman raised a new castle, and in doing that he laid some twenty-nine houses low.