HADRIAN'S WALL, the name usually given to the remains of the Roman fortifications which defended the northern frontier of the Roman province of Britain. It extends from Wallsend on the estuary of the Tyne to Bowness on the Solway, cir. 734 English miles, and was erected by order of the Emperor Hadrian under Platorius Nepos, governor of Britain cir. A.D. 122-126. The com plete work was not built to a single plan, but reached its final form (probably within the years stated) by three stages: (I) a series of detached forts, each holding 50o men, four miles apart, on an average, lying in front (to the north) of an earthwork (the "Valium") which served as a visible delimitation of the civil frontier of Rome ; the enlargement of certain of. these forts to hold i,000 men; (3) the connection of the forts by a stone wall, and the provision of smaller fortified posts at every mile ("Mile castles") with intervening turrets. This wall was designed rather as a fortified sentry beat than as a defensive fortification. At cer tain points traces have been found of a wall of turf, which pre ceded the stone wall ; this has yet to be elucidated fully, but may be a temporary step in the development between stages 2 and 3. No definite evidence has yet been found that the wall was held by the Romans after A.D. 383. See further BRITAIN : Roman.