work in
Britain, this is plain, that he fixed on the line of Hadrian's wall as his
substantive frontier. His successors, Caracalla and Severus Alexander
(211-235), accepted the position, and many inscriptions refer to building
or rebuilding executed by them for the greater efficiency of the frontier
defences. The conquest of Britain was at last over. The wall of Hadrian
remained for nearly two hundred years more the northern limit of Roman
power in the extreme west.

II. _The Province of Britain and its Military System._--Geographically,
Britain consists of two parts: (1) the comparatively flat lowlands of the
south, east and midlands, suitable to agriculture and open to easy
intercourse with the continent, i.e. with the rest of the Roman empire; (2)
the district consisting of the hills of Devon and Cornwall, of Wales and of
northern England, regions lying more, and often very much more, than 600
ft. above the sea, scarred with gorges and deep valleys, mountainous in
character, difficult for armies to traverse, ill fitted to the peaceful
pursuits in agriculture. These two parts of the province differ also in
their history. The lowlands, as we have seen, were conquered easily and
quickly. The uplands were hardly subdued completely till the end of the 2nd
century. They differ, thirdly, in the character of their Roman occupation.
The lowlands were the scene of civil life. Towns, villages and country
houses were their prominent features; troops were hardly seen in them save
in some fortresses on the edge of the hills and in a chain of forts built
in the 4th century to defend the south-east coast, the so-called Saxon
Shore. The uplands of Wales and the north presented another spectacle. Here
civil life was almost wholly absent. No country town or country house has
been found more than 20 m. north of York or west of Monmouthshire. The
hills were one extensive military frontier, covered with forts and
strategic roads connecting them, and devoid of town life, country houses,
farms or peaceful civilized industry. This geographical division was not
reproduced by Rome in any administrative partitions of the province. At
first the whole was governed by one _legatus Augusti_ of consular standing.
Septimius Severus made it two provinces, Superior and Inferior, with a
boundary which probably ran from Humber to Mersey, but we do not know how
long this arrangement lasted. In the 5th century there were five provinces,
Britannia Prima and