It is not necessary to pursue the operations of Agricola further. In the seventh summer he defeated Galgacus on the flanks of the Grampians. The Roman power was now at its height. Agricola, probably from motives of jealousy, was recalled by the emperor Domitian, and as his successors were not men of the same vigour as himself, the barbarians were in a condition, at least to dispute the pretensions of their conquerors. [Sidenote: HADRIAN ARRIVES IN BRITAIN.] In the year 120—thirty-five years after the recall of Agricola—affairs in Britain had fallen into such confusion, as to require the presence of the emperor HADRIAN, who had assumed the imperial purple three years before. He did not attempt to regain the conquests which Agricola had made in Scotland, but prudently sought to make the line of forts, which that general had constructed in his second campaign, the limit of his empire. With this object in view, he drew a wall across the island—the BARRIER of the LOWER ISTHMUS. The testimony of Spartian, the historian of his reign, though brief, is decisive. Hadrian, says he, visited Britain, when he corrected many things, and first drew a wall (_murus_) eighty miles in length, to divide the barbarians from the Romans. The arrival in Britain, of Hadrian, one of Rome’s greatest generals, was thought an event of sufficient importance to be commemorated in the currency of the empire. The large brass coin, here represented, was struck by decree of the Senate in the year 121.[3] [Illustration] [Sidenote: THE BARRIER OF THE UPPER ISTHMUS.] The plans and the prowess of the emperor were thought to have effectually secured those portions of the island, which it was prudent to retain in the grasp of Rome. This circumstance was announced to the world in another coin, bearing, on the reverse, a name destined to sound through regions Hadrian never knew—BRITANNIA—and representing a female figure seated on a rock, having a spear in her left hand, and a shield by her side.[4] [Illustration] About twenty years after Hadrian’s expedition, Lollius Urbicus took the command in Britain. He was not satisfied with the limits which Hadrian had prudently assigned to the empire in Britain. Forcing back the Britons, he raised an earthen rampart across the isthmus between the Forth and the Clyde. Graham’s Dike, in Scotland, is the wall which was built by Lollius Urbicus. This is proved by the numerous sculptures which have, at different times, been discovered among its ruins. [Sidenote: DECLINE OF THE ROMAN POWER.]