Caracalla himself was assassinated in 217, but emperors of his kindred wore the imperial purple down to the year 235, and thus the dynasty of Severus may be said to have lasted for more than forty years. Both in coins and inscriptions the princes of this house have left an exceptionally full record in the British province. From 235, the date of the murder of Severus Alexander (an excellent young emperor, last of his line), down to 284, a period of almost half a century, the Roman empire was in a state of absolute disintegration. The barbarians were pressing fiercely on its frontiers. This was the era of the first and terrible invasion of the Goths (244–270), an invasion which after awful losses on both sides, and the death of a Roman emperor from the pestilence caused by the war, ended in the abandonment to the barbarians of the great province of Dacia, won for the empire by the victories of Trajan. It was the era, too, of a most humiliating defeat by the Persians, and the conversion of a Roman emperor into a footstool for the Persian king. But more dangerous, if possible, than the external foes of the empire, was its internal disorganisation. In these forty-nine years no fewer than fifteen emperors were recognised at Rome, besides a multitude of obscure competitors (commonly known as the thirty tyrants) in the provinces. It is needless to say that the reigns, which thus lasted on an average little more than three years, were generally terminated by mutiny and murder; needless to dilate on the miserable collapse of law and order which inevitably followed from such continual changes in the depositary of supreme power in the state. Of this dismal period there is, naturally enough, no written record in the annals of Britain. Undoubtedly the wave of Roman influence ebbed; we can hardly be wrong in thinking that now, at any rate, if not before, the country between the two walls was permanently abandoned to the barbarians. The Northumbrian camps were probably also sacked, and we may, if we will, read some pages of that long unwritten chapter in the ruined walls of the camps erected by Hadrian and Severus, in the places where fire has evidently passed upon the corridors of a Roman villa, destroying the elaborate bathing arrangements of tribune or centurion.