According to Caesar, the _Matrona_ and _Sequana_ formed the frontier between Celtic Gaul and the Belgae. This is generally understood, as if those rivers had always been the permanent line of separation between the two nations, but if this had been the case, we should not be able to understand how the inhabitants of Lower Britany could be of the same race as the Belgae. In order to account for this fact, people have had recourse to an immigration, and it is alleged that, owing to the influx of Angli, Saxons, and Frisians into Britain, a part of the British population quitted their native island and settled in Lower Britany. But this alleged colony of Britons is not supported by any historical evidence; the writers of the fifth century say nothing about it, and what they do say, does not refer to an immigration, but to the fact that a part of Armorica, in the fifth century, made itself independent of Rome. We may assert, on the contrary, that, at an earlier period, the Cymri inhabited a much greater part of Gaul, and that in Lower Britany alone they maintained themselves against the invading Celts, while Normandy and the other countries were conquered by the Gael. The physical nature of Lower Britany also was favourable to its isolation; marshes and forests render it inaccessible, whence the inhabitants also remained free from Roman contagion. In this manner, the Cymrian element was preserved against the influence of the Gauls. In the fourth and fifth centuries, the northern coast from the Loire to the frontier of the Netherlands, was called _Tractus Aremoricus_ or _Aremorica_ which in Celtic signifies “maritime country.” The commotions of the third century, which continued to increase during the fourth and fifth, repeatedly drove the Romans from that country. French antiquaries imagine that it was a regularly constituted Gallic republic, of which Chlovis had the protectorate, but this is wrong.