Cæsar stayed but three weeks in the country, and may not have visited Dover; but as, when he returned in the following year with a much larger force, he seems to have embarked and landed at the same points, he must have been familiar with the aspect of the port from the sea. As on this occasion he traversed Kent and crossed the Thames, he probably left no dangerous force behind him at Dover, which he does not mention, and which clearly was not then made a rallying point by the Britons. Had the heights been held in force, he would probably in the first instance have reduced them, or at any rate have mentioned the fact in his narrative. During the century that followed Cæsar’s appearance, Rome took no active part in British affairs, but it is probable that a considerable trade sprang up between the island and the Continent, and the Britons made great advances in commerce and civilisation. Towns were founded and coins struck. The next military invasion took place, A.D. 43, ninety-eight years after the first appearance of Cæsar, and under the reign of Claudian, and command of Aulus Plautius, who landed with four legions. The Cantii then held a tract nearly corresponding to the present county of Kent. Durovernum had been founded amidst its indigenous alders, and Camalodunum, beyond the Thames, was the chief city of the Trinobantes. Where Plautius landed is not precisely known. Probably at several points on the open beach between Rich borough and Laymen. Whether the Britons mustered north or south of the Thames is also unknown; but, when Claudian followed his lieutenant, the way lay open to that river, and he marched at once upon Camalodunum, where the Trinobantes were put to flight. Plautius probably subdued the country as far west as the Axe and the Tamar, and his progress may, it is thought, be traced by the remains of his rectangular camps opposed to those of larger area and irregular outline thrown up by the retiring Britons. As, in the year A.D. 40, Caligula had caused a lighthouse to be set up on the heights of Boulogne, it is not improbable that Plautius was the builder of the corresponding tower at Dover.