570 APPENDIX ON THE ROMAN-BRITISH 
The condition of this island, improved by two centuries and 
a half of Eoman civilization, was at that time highly pros- 
perous. "Non mediocris " (says Eumenius), "jactura erat 
reipublicee terra, tanto frugum ubere, tanto Iseta munere 
pastionum, tot metallorum fluens rivis, tot vectigalibus qu^estuosa, 
tot accincta portubus, tanto immensa circuitu," Carausius 
became a considerable potentate — in naval power, especially, 
superior to the Romans ; who, since their conquest of all the 
countries bordering on the Mediterranean, had neglected maritime 
warfare. Maximian in vain attempted an expedition against 
him ; and in A.D. 289 terms of peace were agreed to, by which 
that prince and Diocletian recognised him as (in Britain) their 
partner in the empire. 
When, however (a.d. 292), Constantius and Galerius were 
created " Csesars " (or presumptive successors to the empire), Con- 
stantius, to whom the government of Gaul, Spain, and Britain 
was assigned, lost no time in attacking Boulogne and reuniting 
to the empire that and the other continental possessions which 
Carausius still held. But no invasion of Britain appears to have 
been then apprehended. 
In A.D. 294 Carausius was assassinated by his friend and minis- 
ter, Allectus, who himself assumed the ])urple in Britain. Pre- 
parations were now made by the Eoman emperors for an invasion ; 
and in the third year of Allectus (a.d. 296) Constantius, having 
collected two fleets of transports, one at Boulogne and the other 
at the mouth of the Seine, set sail with a considerable force 
from both ports simultaneously (himself embarking at Boulogne), 
with contrary winds, and in thick, foggy weather. Part of the 
expedition lost its way, and eventually sailed up the Thames to 
London ; the main body, with Constantius himself and his 
Praetorian prefect Asclepiodotus, made for the British coast op- 
posite the Isle of Wight near which the navy of Allectus was 
on the look-out for them. Under cover of the fog, that part of 
the force which was under the command of Asclepiodotus 
passed unseen by the British fleet, and effected a landing, 
setting fire, immediately afterwards, to their ships. Allectus 
who was in possession of the neighbouring port (doubtless 
Portsmouth), and encamped upon the shore, hastily abandoned 
