He cut canals, with vast labor and expense, through all the low eastern parts of Britain, at the same time draining those fenny countries, and promoting communication and commerce.  On these canals he built several cities.  Whilst he thus labored to promote the internal strength and happiness of his kingdom, he contended with so much success against his former masters that they were at length obliged not only to relinquish their right to his acquisition, but to admit him to a participation of the imperial titles.  He reigned after this for seven years prosperously and with great glory, because he wisely set bounds to his ambition, and contented himself with the possession of a great country, detached from the rest of the world, and therefore easily defended.  Had he lived long enough, and pursued this plan with consistency, Britain, in all probability, might then have become, and might have afterwards been, an independent and powerful kingdom, instructed in the Roman arts, and freed from their dominion.  But the same distemper of the state which had raised Carausius to power did not suffer him long to enjoy it.  The Roman soldiery at that time was wholly destitute of military principle.  That religious regard to their oath, the great bond of ancient discipline, had been long worn out; and the want of it was not supplied by that punctilio of honor and loyalty which is the support of modern armies.  Carausius was assassinated, and succeeded in his kingdom by Allectus, the captain of his guards.  But the murderer, who did not possess abilities to support the power he had acquired by his crimes, was in a short time defeated, and in his turn put to death, by Constantius Chlorus.  In about three years from the death of Carausius, Britain, after a short experiment of independency, was again united to the body of the Empire.

[Sidenote:  A.D. 304]

Constantius, after he came to the purple, chose this island for his residence.  Many authors affirm that his wife Helena was a Briton.  It is more certain that his son Constantine the Great was born here, and enabled to succeed his father principally by the helps which he derived from Britain.

[Sidenote:  A.D. 306.]

Under the reign of this great prince there was an almost total revolution in the internal policy of the Empire.  This was the third remarkable change in the Roman government since the dissolution of the Commonwealth.  The first was that by which Antoninus had taken away the distinctions of the municipium, province, and colony, communicating to every part of the Empire those privileges which had formerly distinguished a citizen of Rome.  Thus the whole government was cast into a more uniform and simple frame, and every mark of conquest was finally effaced.  The second alteration was the division of the Empire by Diocletian.  The third was the change made in the great offices of the state, and the revolution in religion, under Constantine.