Roman Cumbria to Wallsend on the Tyne estuary, with additional military installations running down the Cumbrian coast from Bowness to Risehow, south of Maryport, in an integrated fashion (and with forts at Burrow Walls and Moresby that were perhaps not part of the system). Historians believe that the Turf Wall from the River Irthing to Bowness-on Solway was rebuilt in stone in two stages. The most easterly five miles were rebuilt at the time of Hadrian, with the remainder being rebuilt after 150 AD. However, this is open to dispute: it is uncertain whether the building works in the second half of
Firth locally the change is held to be at the Tail of the Bank where the river crosses a sandbar off Greenock at the junction to the Gare Loch, or even further west at Gourock point. However, some firths are exceptions. The Cromarty Firth on the east coast of Scotland, for example, resembles a large loch with only a relatively small outlet to the sea and the Solway Firth and the Moray Firth are more like extremely large bays. The Pentland Firth is a strait rather than a bay or an inlet. These are connected to, or form part of, the