Westward from this mile-castle the Wall climbs Burnhead Crag, on which the foundations of a building, similar to the turrets, were exposed a few years ago; then it dips down again to Haltwhistle Burn, which comes from Greenlee Lough, and is called, until it reaches the Wall, the Caw Burn. From the burn a winding watercourse supplied the Roman station of AEsica (Great Chesters) with water. Just here the Wall is in a very ruinous condition; and of the station of AEsica but little masonry remains, though the outlines of it can he clearly traced. Beyond AEsica, however, is a splendid portion of the Wall, standing some seven or eight courses high. Here it climbs again to the top of the crags which once more appear, bold and rugged, to culminate in the "Nine Nicks of Thirlwall," so called from the number of separate heights into which the crags divide, and over which the Wall takes its way.
At Walltown, on this part of its course, is to be seen an old well, in which Paulinus is said to have baptised King Edwin; but the local name for it is King Arthur's Well. Now the Wall descends to a level and pastoral country, leaving behind it the wild moorland and craggy heights across which it has travelled so long; but unfortunately much of it has been destroyed by the quarrying operations at Greenhead. Of the station of Magna (Caervoran) little can be seen at the present day. This station and Aesica are nearer to each other than are any other two stations on the Wall, and a line of camps, five in number, stand south of the Wall and Vallum, from Magna to Amboglanna, showing that a third line of defence was deemed necessary where the natural defences of moorland ridge, lough or crag were absent.
The Roman way called the Stanegate comes from the eastward almost up to the station of Magna, which stands a little to the south of both Wall and Vallum, between them and Wade's road, which here approaches nearer to the Wall than it has done for many miles.
Another Roman road, the Maiden Way, comes from the South closely up to the Vallum, quite near to Thirlwall castle. The name "Thirlwall" was supposed to commemorate the "thirling" (drilling or piercing) of the Wall at this point by the barbarians, but this is extremely doubtful; though the difficulty of defending the wall on this level tract lends an air of likelihood to this supposition. Near here the little river Tipalt flows across the line of the Wall on its way southward to join the North Tyne.
