Secunda, Flavia and Maxima Caesariensis and (for a
while) Valentia, ruled by _praesides_ and _consulares_ under a _vicartus_,
but the only thing known of them is that Britannia Prima included
Cirencester.

[Illustration: FIG. 1.--Plan of Housesteads (Borcovicium) on Hadrian's
Wall.]

The army which guarded or coerced the province consisted, from the time of
Hadrian onwards, of (1) three legions, the Second at Isca Silurum
(Caerleon-on-Usk, _q.v._), the Ninth at Ebur[=a]cum (_q.v._; now York), the
Twentieth at Deva (_q.v._; now Chester), a total of some 15,000 heavy
infantry; and (2) a large but uncertain number of auxiliaries, troops of
the second grade, organized in infantry cohorts or cavalry _alae_, each 500
or 1000 strong, and posted in _castella_ nearer the frontiers than the
legions. The legionary fortresses were large rectangular enclosures of 50
or 60 acres, surrounded by strong walls of which traces can still be seen
in the lower courses of the north and east town-walls of Chester, in the
abbey gardens at York, and on the south side of Caerleon. The auxiliary
_castella_ were hardly a tenth of the size, varying generally from three to
six acres according to the size of the regiment and the need for stabling.
Of these upwards of 70 are known in England and some 20 more in Scotland.
Of the English examples a few have been carefully excavated, notably
Gellygaer between Cardiff and Brecon, one of the most perfect specimens to
be found anywhere in the Roman empire of a Roman fort dating from the end
of the 1st century A.D.; Hardknott, on a Cumberland moor overhanging Upper
Eskdale; and Housesteads on Hadrian's wall. In Scotland excavation has been
more active, in particular at the forts of Birrens, Newstead near Melrose,
Lyne near Peebles, Ardoch between Stirling and Perth, and Castle Cary,
Rough Castle and Bar Hill on the wall of Pius. The internal arrangements of
all these forts follow one general plan. But in some of them the internal
buildings are all of stone, while in [v.04 p.0585] others, principally (it
seems) forts built before 150, wood is used freely and only the few
principal buildings seem to have been constructed throughout of stone.

We may illustrate their character from Housesteads, which, in the form in
which we know it, perhaps dates from Septimius Severus. This fort measures
about 360 by 600 ft. and covers a trifle less than 5 acres. Its ramparts
are of stone, and its north rampart coincides wit