The high crags which here shoulder the Wall are part of the Great Whin Sill, an intrusive dyke of dolerite which stretches from Greenhead northeastward across the county nearly to Berwick.  The military road here leaves the Wall, with which it does not again come into close contact until both are near Carlisle, though in several places the Roman road will be encountered near the Wall in a well-preserved condition.  The Wall now climbs another ascent to the farmhouse of Sewingshields, which name is variously explained as “Seven Shields,” and as “The shiels (shielings, or little huts) by the seugh” or hollow—­the hollow being the fosse.  Sewingshields Castle, long since disappeared, is the scene of the knight’s adventures in Sir Walter Scott’s “Harold the Dauntless.”  And tradition asserts that King Arthur, with Queen Guinevere and all the court, lies in an enchanted sleep beneath the castle, or at least its site.  Not only is there no castle, but the Wall also has been despoiled to supply the material for building the farmhouse and other buildings in the neighbourhood.  The Wall climbs unfalteringly over the crags, one after the other, until the wide opening of Busy Gap is reached.  This being such a convenient pass from north to south, it was naturally used constantly by raiders and thieves; and such an unenviable notoriety did it possess, that to call a person a “Busy Gap rogue” was sufficient to lay oneself open to an action for libel.  Climbing the next slope we look down on Broomlee Lough and reach the portion of the Wall we have already noted—­Borcovicus (Housesteads), Cuddy’s Crag, Hot Bank farmhouse, and Crag; Lough.

The course of the Wall continues, past Milking Gap, along the rugged heights of Steel Rig, Cat’s Stairs, and Peel Crag, till on reaching Winshields we are at the highest point on the line, 1,230 feet above the sea-level.  Dipping down to Green Slack, the Wall crosses the valley called Lodham Slack, and begins to ascend once more.  The local names of gaps and heights in this neighbourhood are highly descriptive, and sometimes weirdly suggestive; we have had Cat’s Stairs, and now we come to Bogle Hole, Bloody Gap, and Thorny Doors.  A little further west from here the very considerable remains of a mile-castle may be seen, in which a tombstone was found doing duty as a hearth-stone.  The inscription recorded that it had been erected by Pusinna to the memory of her husband Dagvaldus, a soldier of Pannonia.

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.