Let us now revert to the Belgic migrations and consider their bearing on the matter of the Celtic colonisation of Ireland. The Belgae, we have seen, were a Celto-Germanic group which, according to Cæsar and Tacitus, occupied the lands stretching from the Rhine to the Seine and Marne, and expelled from that region the Celtae proper. There is no indication in what Cæsar says that in his time this movement was one of remote antiquity. In fact, it is perfectly clear that it was a movement by no means exhausted but still in active progress when he took command of the Roman armies in Gaul. The attempted migration of the Helvetii in the first year of his command, B.C. 58, was a part of this movement. A little later, Cæsar had to repel similar attempts of the Usipetes and the Tencteri to cross the middle Rhine and settle in Gaul; and these, according to Dio, were two Celtic peoples. Still later, in the time of Augustus, the Ubii migrated from the eastern to the western side of the Rhine. From all this it is clear that the Belgic migration was a continuous movement and that its force was far from being spent at the time of the Roman conquest of the country west of the Rhine. Cæsar indicates that there were powerful Belgic settlements west of the Rhine during the great wandering movement of the Cimbri and the Teutones, _i.e._, about half a century before he began his Gallic campaigns. There is nothing, however, to show that these settlements were of earlier date than the second century B.C., and I have seen no reason for thinking that they could have been much earlier. We now come to the question of the Belgic invasion of Britain and its probable date. In Rhys's theory, which is still accepted in England, the Belgic invaders were the first to establish the Iron Age in Britain. I claim to have shown good grounds for believing that there was no Celtic occupation of Britain before the Iron Age. I have already suggested that, if this Celto-Germanic movement was brought to a standstill on the banks of the Marne, it was not likely to have succeeded in over-running all England at the commencement of the Iron Age in England. It will be seen that the Celto-Germanic migrations extended not merely to Britain but also to Ireland, and I suggest that if these Celto-German Belgae had been the first people to come over armed with iron, they would have made an easy conquest of Ireland as well as of England. Let us look at the actual evidence of the Belgic conquest of England. The sole historical witness on the point is Julius Cæsar, and this is his testimony: