It was the father-in-law of Tacitus, Julius Agricola, who conquered, or at least defeated, the northern tribes of England. Among the powerful Brigantes he established a garrison at York (Eburacum), which eventually became the most important of all the Roman centres. He advanced into Scotland also, and inflicted a bloody defeat upon the wild Caledonians. But Scotland remained unconquered, as did the neighbouring island upon which also Agricola had cast his ambitious eyes. The Roman army was wanted elsewhere, and the Emperor Domitian declined to assist any further adventures. Little more of our island’s story is recorded until the travelling Emperor Hadrian came out to visit us in A.D. 122. He saw that the wild north was only to be won by a gradual advance with more or less peaceful penetration northwards. The system of fortified frontiers was already established on the Rhine and Danube, and Hadrian drew his finger across the seventy miles between Bowness and Wallsend. Across this space, where the Tyne and Solway almost overlap, the Roman lines ran straight over hill and dale, and there they are to this day as a silent proof of the greatness of the Roman people.[63] This was more than a frontier: it was a vast elongated camp which looked south as well as north and frowned alike upon the Brigantes and the Caledonians. It was pierced at intervals by fortified gates and great roads ran northwards through it. On the north there was first a ditch, and then a stone wall broad enough for two or three men to walk abreast along it and nearly twenty feet high. Behind this, in a space of about 140 yards wide runs a road connecting a chain of fourteen large camps, some of which grew into towns. Southward again was the quadruple rampart of earth, a mound, a dyke, and then a double mound. This immense labour, though it is small in comparison with Roman works elsewhere, was achieved not by British slaves, but by Roman soldiers, some of whom were Britons, some Spaniards, and some Germans. It was completed gradually under various emperors. There were detached forts both north and south of the wall of Hadrian. It was Antoninus Pius who made the next step twenty years later. The Antonine wall from the Forth to the Clyde is only about half as long and of inferior strength. There were camps even north of this, in Stirlingshire for example, and it is clear that the Romans intended to feel their way into the Highlands. But that was contrary to their fates.