The whole extent of territory that lay between the walls of Adrian and Antoninus, was every where inter sected by Roman roads. But it is doubtful whether the country between the Northern Wall and the Mur ray Frith was formally erected into a Roman province; though it was traversed by roads of communication and overawed by military stations.
Lollius Urbicus was removed from the government of Britain, in consequence of the death of Antoninus Pius. So effectually had the Caledonians been re strained by his vigorous but beneficent policy, that, during his administration, and for several years after his removal, no insurrections took place. But the na tives, impatient of restraint, began to manifest a dis position to revolt. Calphurnius Agricola, being sent into Britain, enforced submission and restored tran quillity. The Romans finding their conquests in Cale donia burdensome, began to contract the limits of the empire; and, during the reign of the Emperor Aurelian, evacuated the military stations beyond the Wall of Autoninus.
During the misrule of the Emperor Commodus, the Caledonians passed the Northern Wall, and ravaged the open country; but being attacked by Marcellus, they retired to the mountains. In repelling these pre datory incursions, the Romans derived neither advan tage nor glory; they therefore concluded a treaty with their turbulent neighbours, in the beginning of the reign of the Emperor Severus, but the peace continued only seven years. Notwithstanding his advanced age, and his bodily infirmities, which obliged him to be transported in a litter, Severus embarked for Britain, attended by his two sons and a formidable army. Upon his arrival he repaired or rebuilt the Wall of Adrian, in order to protect his retreat in case of accidents. He speedily passed the Northern Wall, and penetrated into the country of the Caledonians, without meeting an enemy; but the coldness of the climate, and the se verity of a winter march across the hills and morasses of North Britain, are reported to have cost the Romans fifty thousand men.
Unable to oppose the obstinate attack of the Ro mans, the fugitive Caledonians were compelled to sue for peace, and to surrender a part of their arms and a considerable portion of their territory. The Emperor
then retired beyond the Wall of Adrian, but the bar barians, regardless of the obligation of a treaty, renew ed hostilities, in consequence of which Severus sent another army into their country under his son, Cara calla, with orders to extirpate them; dying at York shortly after, in the sixty-sixth year of his age.
Upon the death of Severus, Caracalla concluded a treaty with the Caledonians, by which he relinquished the territories they had recently surrendered to his fa ther; and he abandoned the forts which had been ed to enforce their submission. The Wall of Antoni nus was fixed as the northern boundary of the Romans. For about a century after this period, the Caledonian tribes remained quiet; and they appear to have profit ed by their intercourse with their late masters; for, during this long interval of peace, they cut down woods, drained marshes, introduced agriculture, con structed, or, more probably, repaired the Roman highways, and built several towns.
From the silence of the classic authors respecting the affairs of Caledonia during the third century, it is probable that the native tribes had devoted their atten tion to the pursuits of peace. The long residence of the Romans iu the island, had improved the rude man ners of the inhabitants, taught them to desire and raise the conveniences of life, and reconciled them to their language and manners.
Of the twenty-one Caledonian tribes, sixteen lived on the north side of Autoninus's Wall. The five south ern tribes, separated for a long period by an impassa ble barrier from the congenerous tribes of the north, felt little interest in the revolutions of the Roman world; but, in the beginning of the fourth century, they had become the objects of jealousy to the north ern tribes, who made irruptions into their territories. The convulsions of the empire had probably rendered it necessary to withdraw the greater part of the troops front the Roman Wall; and thus leaving it compara tively defenceless, to invite the hostile attacks of the secluded Caledonians.