The Vallum is a unique linear earthwork to the south of Hadrian’s Wall. When it was constructed, it ran in an unbroken line, following close to the course of the Wall, from Newcastle to Bowness-on-Solway, a distance of about 112km.
Where possible, the Vallum lies close to the rear of the Wall. However, unlike some sections of the Wall, it is laid out in very long straight sections, avoiding steep gradients, with a few very deliberate corners. In the famous central section where the Wall runs along the crags of the Whin Sill, the Vallum stays in the Valley. Where it crosses very soft ground, as at White Moss in Cumbria, the ditch is not dug in, but created between mounds of material, The ditch is uninterrupted except for causeways that have been found opposite the gates of the main Wall forts, and perhaps some milecastles.
Dating The Vallum
The Vallum followed the Turf west of Birdoswald Fort closely. When this Wall was replaced in stone on a new course further north, probably late in Hadrian’s reign, there was no attempt to move the Vallum.
What was the Vallum for?
The Vallum is unique, which is always a problem to archaeology, where insights so often come from comparing things. While most commentators have draw attention to the road-like nature of its layout, and noted its possible function in communications, they have sought its true function elsewhere. Little has changed in our understanding of this earthwork, as Tony Wilmott, a leading English Heritage archaeologist and Wall specialist, made clear recently:
“The straight lengths in which the Vallum is laid out are consistent with distances of the uninterrupted view of a surveyor. Changes in direction tend to occur where a new viewpoint is required to obtain another long straight view. This is the system used to lay out roads. It has been argued that as the Vallum was surveyed as a road would be, it must have functioned as a road. This does not follow, and if we accept that a road would require metalling, and metalling on the berms is sporadic, and sometimes doubtful, we have to discount all of the suggested variations of a function related to lateral communication.Richmond’s (1930) statement of the function of the Vallum remains valid:
‘the Vallum takes its place as a prohibited zone delimiting the south side of the military area, an unmistakable belt in which an obstacle is provided by the great ditch. Neither commerce nor interference with the soldiery could take place across it unchecked.’ ”
“ It was not a strictly military defensive system, for the ditch is not of military shape, nor are the symmetrical banks defensive; furthermore, the Vallum takes no account of commanding ground. Rather it is a barrier and line of demarcation defining the rear of the Wall-zone, and preventing entry except at fixed points.”
“The Vallum allowed army units to segregate themselves from civilians and to use the zone between the two barriers for grazing military pack animals and cavalry horses.”
The Vallum as an unfinished road
The first task here is to trace furrows, ripping up the maze of paths, and then excavate a deep trench in the ground.
The second comprises refilling the trench with other material to make a foundation for the road build-up.
The ground must not give way nor must bedrock or base be at all unreliable when the paving stones are trodden.
Next the road metalling is held in place on both sides by kerbing and numerous wedges.
Digging the Vallum
- Men with baskets;
- Animals, probably asses/donkeys with baskets [panniers];
- Carts or wagons, probably pulled by asses or oxen.
Since the ground along the steep sides of the trench is potentially unstable, the spoil can only be extracted from either in front, or behind, the excavation, and thus, two possible methods of construction suggest themselves:
Two models for spoil extraction from the Vallum
Reverse extraction: In this method, the spoil is loaded downwards into carts or baskets using the trench to take the spoil out backwards. If the trench face is reduced in spots, all but the lowest can be easily loaded into a cart or baskets, and potentially, the draught animals do the hard work of lifting the material by means of a ramp at the start of a section of the works. In addition, by dumping the material ahead of the trench, it is possible that as the excavation goes forward, the spoil heap moves backward, and so the distance between the two and the time taken to move the spoil remains fairly constant.
The first method relies on human power to lift the spoil from the trench, whereas the second uses draught power for part of this the task, but would move the spoil a greater distance and requires the transport to able to turn in the trench.
The Marginal Mound
The intermittent presence of this feature to the south of the Vallum ditch has probably prompted more debate than anything else. It was once the basis of the belief that the Vallum had been recut. A connection has also been suggested between the backfilling of the Vallum to create causeways, and the presence of the marginal mound.
"When I see a bird that walks like a duck and swims like a duck and quacks like a duck, I call that bird a duck."
- Laid out in straight lengths;
- Gentle corners;
- Avoids steep or uneven gradients;
- Avoids soft ground;
- Where it had to cross soft ground, the central trench is formed between earth banks;
- Follows close behind the wall and forts;
- Starts from a bridgehead at Newcastle;
- It has been suggested there were originally gaps in the northern spoil mound corresponding to milecastles.
Part 3; The construction of Hadrian's First Wall here