tely
to the central government at Rome, had obviously become outgrown. And
the Provinces themselves were much too large. Diocletian accordingly
began by dividing the Empire into four "Prefectures," two in the east
and two in the west. Each pair was to be under one of the co-Augusti,
who again was to entrust one of his Prefectures to the "Caesar"[324]
or heir-apparent of his choice. Thus Diocletian held the East,
while Galerius, his "Caesar," took the Prefecture of Illyricum. His
colleague Maximian, as Augustus of the West, ruled in Italy; and the
remaining Prefecture, that of "the Gauls," fell to the Western
Caesar, Constantius Chlorus. Each Prefecture, again, was divided into
"Dioceses" (that of Constantius containing those of Britain, Gaul,
Spain, and Mauretania), each under a "Vicar," and comprising a certain
number of "Provinces" (that of Britain having four). Thus a regular
hierarchy with rank above rank of responsibility was established,
and so firmly that Diocletian's system lasted (so far as provincial
government was concerned) till the very latest days of the Roman
dominion.

A. 6.--When Constantius thus became Caesar of the West, his first
task was to restore Britain to the Imperial system. He was already, it
seems, connected with the island, and had married a British lady
named Helen.[325] Their son Constantine, a youth of special promise
(according to the panegyrists), had been born at York, about A.D.
274, and now appeared on the scene to aid his father's operations
with supernatural speed, "_quasi divino quodam curriculo_."[326]
Extraordinary celerity, indeed, marked all these operations. Allectus
was on his guard, with one squadron at Boulogne to sweep the coast
of Gaul, and another cruising in the Channel. By a sudden dash
Constantius [in A.D. 296] seized the mouth of Boulogne harbour, threw
a boom across it, "_defixis in aditu trabibus_," and effectually
barred the pirates from access to the sea.[327] Meanwhile the fleet
which he had been building simultaneously in various Gallic ports was
able to rendezvous undisturbed at Havre.

A. 7.--His men were no expert mariners like their adversaries; and,
for this very reason, were ready, with their Caesar at their head,
to put to sea in threatening weather, which made their better-skilled
pilots hesitate. "What can we fear?" was the cry, "Caesar is with us."
Dropping down the Seine with the tide on a wild and rainy morning,
they set sail with a cross wind,