This plan particularly affected Britain. All the conquests of Agricola to the northward of the Tyne were relinquished, and a strong rampart was built from the mouth of that river, on the east, to Solway Frith, on the Irish Sea, a length of about eighty miles. But in the reign of his successor, Antoninus Pius, other reasonings prevailed, and other measures were pursued. The legate who then commanded in Britain, concluding that the Caledonians would construe the defensive policy of Adrian into fear, that they would naturally grow more numerous in a larger territory, and more haughty when they saw it abandoned to them, the frontier was again advanced to Agricola's second line, which extended between the Friths of Forth and Clyde, and the stations which had been established by that general were connected with a continued wall. [Sidenote: A.D. 207] [Sidenote: A.D. 208] [Sidenote: A.D. 209] From this time those walls become the principal object in the British history. The Caledonians, or (as they are called) the Picts, made very frequent and sometimes successful attempts upon this barrier, taking advantage more particularly of every change in government, whilst the soldiery throughout the Empire were more intent upon the choice of a master than the motions of an enemy. In this dubious state of unquiet peace and unprosecuted war the province continued until Severus came to the purple, who, finding that Britain had grown into one of the most considerable provinces of the Empire, and was at the same time in a dangerous situation, resolved to visit that island in person, and to provide for its security. He led a vast army into the wilds of Caledonia, and was the first of the Romans who penetrated to the most northern boundary of this island. The natives, defeated in some engagements, and wholly unable to resist so great and determined a power, were obliged to submit to such a peace as the emperor thought proper to impose. Contenting himself with a submission, always cheaply won from a barbarous people, and never long regarded, Severus made no sort of military establishment in that country. On the contrary, he abandoned the advanced work which had been raised in the reign of Antoninus, and, limiting himself by the plan of Adrian, he either built a new wall near the former, or he added to the work of that emperor such considerable improvements and repairs that it has since been called the Wall of Severus.