h the great wall of
Hadrian. Its interior is filled with stone buildings. Chief among these
(see fig. 1), and in the centre of the whole fort, is the Headquarters, in
Lat. _Principia_ or, as it is often (though perhaps less correctly) styled
by moderns, _Praetorium_. This is a rectangular structure with only one
entrance which gives access, first, to a small cloistered court (x. 4),
then to a second open court (x. 7), and finally to a row of five rooms (x.
8-12) containing the shrine for official worship, the treasury and other
offices. Close by were officers' quarters, generally built round a tiny
cloistered court (ix., xi., xii.), and substantially built storehouses with
buttresses and dry basements (viii.). These filled the middle third of the
fort. At the two ends were barracks for the soldiers (i.-vi.,
xiii.-xviii.). No space was allotted to private religion or domestic life.
The shrines which voluntary worshippers might visit, the public bath-house,
and the cottages of the soldiers' wives, camp followers, &c., lay outside
the walls. Such were nearly all the Roman forts in Britain. They differ
somewhat from Roman forts in Germany or other provinces, though most of the
differences arise from the different usage of wood and of stone in various
places.

Forts of this kind were dotted all along the military roads of the Welsh
and northern hill-districts. In Wales a road ran from Chester past a fort
at Caer-hyn (near Conway) to a fort at Carnarvon (Segontium). A similar
road ran along the south coast from Caerleon-on-Usk past a fort at Cardiff
and perhaps others, to Carmarthen. A third, roughly parallel to the shore
of Cardigan Bay, with forts at Llanio and Tommen-y-mur (near Festiniog),
connected the northern and southern roads, while the interior was held by a
system of roads and forts not yet well understood but discernible at such
points as Caer-gai on Bala Lake, Castle Collen near Llandrindod Wells, the
Gaer near Brecon, Merthyr and Gellygaer. In the north of Britain we find
three principal roads. One led due north from York past forts at Catterick
Bridge, Piers Bridge, Binchester, Lanchester, Ebchester to the wall and to
Scotland, while branches through Chester-le-Street reached the Tyne Bridge
(Pons Aelius) at Newcastle and the Tyne mouth at South Shields. A second
road, turning north-west from Catterick Bridge, mounted the Pennine Chain
by way of forts at Rokeby, Bowes and Brough-under-Stainmoor, descended into
t