02 August, 2019

Understanding Hadrian's Wall part 2 - Building a Myth in Video Form

This is part 2 of my video version of my Understanding  Hadrian's Wall talk, available locally on request, free to a good home.
Hopefully, some of the technical aspects have improved over part 1.
A brief summary of part 1 is accompanied by mildly banging music, despite the risks inherent risks in raising expectations on raising peoples expectations.
This will probably be cut down to become an standard intro to any future TSA videos.
The third part of Understanding Hadrian's Wall ~ The Hidden Disaster will have a full list of credits etc. It may even be possible to create a final summary video that runs for a modest length of time - with the mistakes taken out, and a more even quality.
The intended audience of the original talks, the passing trade at The Twice Brewed Inn, could not be assumed to have any detailed background in the archaeology of the period, so it was important the establish the geographical, social and historical background.

If directed at archaeology students or enthusiasts, it can be done in an hour, although 20 minute conference slot is a waste of time, unless you go full on blitzkrieg mode.  Unfortunately, the inherent scepticism of the scientific and evidence based reasoning of Structural Archaeology is not always welcome in an environment where people have job for life in a monopoly and are judged by their conformity, and their knowledge of Latin, not soil science.

Many thanks again to Andy for his continued support and patience - I will return to proper archaeology soon, and leave the Imperialist pig-dogs with their regular buildings and running water - what did they ever do for us?

07 July, 2019

Understanding Hadrian's Wall in slowly moving pictures with sound

 A recent episode of illness, has made me reconsider my route to market and the future of this blog.  I have been working on a book, but the complexities of 3D modelling are not well suited to text.
However, there is another darker issue; my work will not be accepted while I am alive.
As a result of my year as a postgrad at Newcastle University, the use of engineering to understand the archaeology of engineered structures, and more specifically, in this case Hadrian’s Wall, has been ruled worthless and without value, although it might have been considered a courtesy to have read it first. However, in a mindless dystopian world governed by a code academic omertà, I am now verboten, persona non grata, outcast in a vale of tribulation and mixed metaphor. 
Having been sentenced to a life of the living dead, where only my demise will make this form evidence acceptable, I not going to pull any punches.
If, in less than an hour, you can deconstruct a course that costs students hundreds, if not thousands of pounds, discouraging people waste their money studying archaeology at these bottom feeding Russel brand universities is a public service. 
If, as in this case, people are being charged real money for a bunch of ill-assorted ideas that were nonsense when they dreamt up by medieval monks and Victorian gentlemen, but have been passed on for generations with all the credulous zeal and fact checking of a medieval scriptorium, - don’t expect acquiescence from any archaeologist with a passing acquaintance with soil science.
I am starting with the Hadrian’s Wall, as it is relatively simple archaeology, and while much of the contemporary narrative is immutable balderdash, it can’t hold a candle to imaginary ritual landscape that illuminates contemporary British Prehistory, a topic I have promised [Andy] to return to. 
While I was confined to YouTube by illness, I was amazed to discover that ancient civilisations of pyramid builders had been found on Mars and well as under the Ice Caps, just one of the many things that archaeologists like me have been keeping secret. I must have had a stroke and forgotten everything.   But then again, someone taught the Sumerians to use Tablets several millennia before the advent of the Samsung Galaxy - it makes you think, or why else would tens of thousands of people rush to watch these videos within hours of them being posted……..
..  So I resolved to find some eccentric item of dress, perhaps a hat, rent the whole wall of books, liberally sprinkle it with extraneous exotic artefacts, perhaps a weapon or two, and a model of Stonehenge descending from the ceiling surrounded by dancing …….
….. After I recovered sufficiently from whatever pestilence was attacking my temporal gland, I decided it would be best if I reproduced the talk that I was giving on The Wall last year at the Twice Brewed Inn.  I already had the slides, so there was no reason for me to become visually involved, that’a a treat reserved for the real people who come to the real thing, and not something to expose to all the imaginary virtual people on YouTube.  
All you have to do is keep talking for 60 minutes without making too many mistakes, while recording it to a reasonable standard, and after all, people who have time to find pyramid shaped rocks on Mars seem to manage it, so how hard could it be?
The creative process has been interesting, in its most ironic and antonymous sense,or so my Production Executive Tiny informs me, although he is partial to a good animation.  We have been learning together, so hopefully, future output ~ Parts 2 & 3, will be of a more consistent standard and quicker to produce.
The video aims to explain Hadrian’s attempt to build his Wall, using the very latest structural research and modelling. This is the first instalment of a three part presentation originally intended for people from all over the world who come to walk the Wall.  Therefore, it assumes little prior knowledge, and is a general introduction to Hadrian & the Romans in the North of Britain in the period 122 ~ 138.
In this introduction, I have to cover much well trodden ground, but as a general rule, I don’t want to waste time telling you what you could read in any guide book.
It lasts 37 minutes; there are no sweeping shots of the modern landscape peppered with snow, accompanying blaring trumpets heralding marching feet, and a booming voice telling you about a distant frontier of the greatest empire the world has ever hyperbolised - that’s all on order with the shed load of books, the sharp suit and the eye-catching neckwear.
So look out for more video content on my new YouTube Channel;

20 February, 2019

Hadrian's Imaginary Border Wall - That Didn't Work

Imaginary Walls

In AD 122, Emperor Hadrian’s first Imperial tour brought him to the Roman province of Britannia, and more specifically its Northern Border.  Here he imagined a great stone wall from sea to shining sea built by his army with the support of the Native population; what he got was a complete disaster.
This is not the Wall that Hadrian or later generations imagined; the evidence for the failure of this policy has been lost in our simplistic picture of this largely non-existent monument and more generally in our admiration of the Romans.
As the most politically powerful politician in the West, he could not only order and fund its construction, but he could also insist that the Natives cooperate in helping wall themselves off from the rest of the Island.   While on level it can be seen as autocratic gesture politics, a very physical symbol of Hadrian’s new policy of territorial and cultural consolidation, it was also an attempt to solve a very real border security issue. 
The Wall is largely an imaginary thing; about 10% has survived in some consolidated form, and while it is not unimpressive in its setting, you have to mostly make it up above waist high.   Despite this, it has lived large in our collective imagination as an artist’s impression, with its own tradition of visual representation.
However, the Wall was a real engineering project, so it can be modelled mathematically in terms of its logistics, planning and execution. What the numbers and archaeology imply is that the project failed, catastrophically, and within a couple of years the wheels had come off this Emperor's plans to build a border wall.

"Walls work....”
“They say 'a wall is medieval.' Well, so is a wheel. A wheel is older than a wall.“
President Donald J Trump, Jan 2019
The past has always been subject to political and cultural misappropriation, it is perhaps why we need to invent it.  However, the recent assertion on the nature of Walls represents a remarkable challenge to the accepted norms of education, rationality and intelligence in an executive skill set. While it might be considered politically incorrect to mock such disability, I would be failing in my responsibility as a structural archaeologist not to fact-check this particular missive, as well as celebrate more generally this remarkable historical nadir in administrative competency and political duplicity.
However, much as it tempting to try and draw parallels with current politics, particularly with the USA, any superficial correspondence is mainly derived from the use of similar terms.   The Romans had no concept of self-governance by anyone and for anyone except as it applied to the relatively small and restricted gene pool of the senatorial class.   This Roman aristocracy had accepted necessity of autocracy, but importantly, among a self-selecting group, it was a meritocracy that ensured a degree of competence and experience in its officials, particularly its chief executive officer.

Cognitive Dissonance.
Even though all representations of Hadrian's Wall are imaginary, this idea of failure probably  conflicts with our picture of a great stone Wall from sea to shining sea, as well as our general positive view of Roman achievement.
Primarily through religion and the remarkable persistence of Latin literacy, The Romans have been woven so deeply into the fabric of Western Culture that we no longer perceive the joins.  Notably, they are the fall-back cultural reference to invoke ideas of power, strength, authority, stability and order.  The Romans were part of our childhood; they had a walk on part in the bible, and usually form one of our earliest educational explorations of History.
This is a pictorial world, from the quaint anachronisms of medieval stained glass to the pulsating classical re-imaginings of Hollywood our culture has sought and consumed a visual past.  Much of our cultures fictional world exists in the past where it merges with whatever actuality is understood at the time.  It’s the past’s self-serving plasticity that drives much of our culture, and it is against this composite magical, heroic, romantic, self-propagating backdrop of our collective imagination that archaeologists must attempt to function.
Importantly, our Latin based classical world existed long before the advent of Archaeology, and as a consequence, excavation data has often been approached from the perspective of an existing literary tradition.  Thus, for many reasons, the dark secret of this failure had long been beyond the imagination of classical scholarship, but the archaeology tells a different story.
The Wall as numbers
The essential difference between imagining or drawing a structure and actually building a real one is Maths. Using numbers is the principle tool of abstraction by which engineers implicitly or explicitly create, plan and execute a successful design.  Given the simplicity of the concept of a mortared stone wall, albeit a “New technology” in this context, apart from the bridges, the project is mainly a problem of logistics. The central idea of Theoretical Structural Archaeology is that engineered structures can be modelled mathematically; this has the additional advantage of not approaching the archaeological evidence from a pictorial or literary perspective. 
My current understanding of the structural evidence is based on new mathematical modelling, which strongly suggests the narrative summarised below and fully justifies the characterisation of the project as a disaster
Hadrian’s Backstory; A Senatorial Class act
Broadly, by the time of Hadrian, real political power in Rome still rested with the 600 senators, even though since Augustus, one of their numbers was chosen to be Emperor.  [There was no written constitution, and the central issue of Roman political history would remain exactly how the process of ‘choosing’ should work].
This self-selecting ruling elite, while living a life of extraordinary privilege, were expected to serve the state, having carefully tailored paid political careers that took them through the army, Law, and administration, even religion, and back again.  An emperor like Hadrian had been a judge, army officer, treasury official, legionary commander, provincial governor, as well as a Consul, one of the two vestigial republican heads of state elected annually.  It is a measure of the stability of the constitutional settlement that Hadrian, who was Consul three times, could also hold one of these offices while also being Emperor.  Therefore it should be understood that the Emperor in this period was a constitutional figure, with specific responsibility and powers.   As Commander in Chief of a standing army of about 250,000 men, his particular role was security, more especially in those provinces of the empire that required a garrison. 
His Biographers assert that Hadrian pursued peace as aggressively as his predecessor Trajan had pursued war.  Trajan’s profitable wars in Dacia had yielded serious amounts of bullion and slaves, however, more recent military adventurism in Iraq had been a disaster, destabilising the region.  As well as problems in the East, Hadrian also seems to have inherited trouble on Western edge of the empire, where in Britain, the army had abandoned Southern and Eastern Scotland, falling back to northern England, where they may have suffered further reverses while Trajan’s attention was elsewhere
Ruling Britannia
Hadrian was the first emperor to visit the Island since Claudius came to celebrate his 'conquest' of Britain nearly eighty years earlier.  The intervening period had seeing a slow and often ineffectual attempt to gain control of the whole island, such that by Hadrian’s time territorial ambitions were restricted to the southern half.
While this represented between 3-4 % of the empire, the loyalty and security of the population was ensured by the presence of 13% of the empire’s troops in the province.  In return for their protection, the natives would have been expected to be provided much of the food and presumably other materials to supply the largest provincial army of occupation anywhere in the Empire.  
The degree to which the Romans had successfully integrated the traditional aristocracies into their own social hierarchy and culture is unclear.  For Hadrian Romanisation was a part of his mission of bringing peace and prosperity, so in addition to commissioning the Wall, he also initiated the development of a new Forum in London, which by this stage had taken over as the governmental and logistical hub for the administration of the Island. 
His coins are the first to have Britannia personified on the reverse, albeit with her head in her hands in a gesture of sorrow or mourning, reminiscent of Dacian coins after Trajan had finished with them.  While not a very auspicious start, it was perhaps appropriate, given that within a few years, London would be burnt, and the Bronze statue commemorating Hadrian’s visit taken from the Forum, smashed and thrown in the Thames.
Why a wall
The strategy of building a Wall adopted by Hadrian was a novel, untried, time consuming and expensive; it was only made possible by the presence of limestone along most of the frontier.
Given that the resources of the Emperor with his court were backing this revolutionary project, we have to assume that the Wall had been planned and costed, presumably to be finished during the governorship of Nepos, i.e. about five years, ending around AD127.  This New Governor of Britain was an important member of Team Hadrian, who had been co-consul with the Emperor, and importantly, he had supervised infrastructure projects for Trajan.
The Wall was piece of military infrastructure, built and manned by the army, which offered a solution to a real security issue.  Put simply; while infantry can climb the Wall, without baggage in the form of pack animals or wheeled transport, and lacking cavalry support, they cannot offer significant threat to the important economic assets further south.  
Viewed from the North, it is equally simple; the objective is to capture a gate, and with one every mile, there were plenty to choose from.
However, even a generous reading of the Romans' intentions would envision a garrison of century per mile, with 40 men in each milecastle and the rest back at one of the forts.   Split that into 3 watches, and we have little more than a dozen men manning two gates, a pair of turrets, and guarding a mile of Wall.  This might challenge many people's vision of the wall with frequent patrols of soldiers marching back and forth ready to fight off disparate groups of attackers trying to climb the Wall; this works for legionary fortress with roughly one man per foot of perimeter, but with less than one man per 100 foot it’s a non-starter.
To put that in perspective, in the only documented major battle against the Highlanders, the Battle of Mons Graupius in 84, the Romans had reportedly defeated a force of around 30,000.  The basic units of auxiliary army units manning the wall are cohorts of 600 men, perhaps up to 1000 when supplemented by cavalry, occupying forts about 7 miles apart, so no milecastle should be much more than an hour from infantry reinforcement.
In theory, the multiple gates give the defenders the counter-attacking options which are typical of a Roman fort, with the prospect of trapping the enemy against the Wall.  However, the nearest Legionary forces were based some hundred miles and several days march to the south, and the garrison alone would find it difficult to concentrate while also maintaining its commitments to manning the Wall’s many fixed positions.
Thus, the Wall can only work if there is sufficient warning of an attack to allow reinforcement of the relevant sections and the pre-positioning appropriate resources.  Without good intelligence, the enemy can turn up in force unexpectedly, or outflank the frontier using the Sea, in which case the strategic situation could deteriorate very quickly for the defenders.  The previous border was more typical, with a series of forts linked by a road; presumably this had proved too porous, with hostile forces passing undetected through this screen, resulting in sufficient military loss to prompt such a radical and expensive solution.
As a consequence, Hadrian’ decision to build his Wall is an important insight into the political situation at the time.  It is simply not realistic to imagine that the territory north of the Wall, immediately adjacent to the largest military garrison in the Empire, was anything other than cooperative and acting as a buffer against hostile elements further north.  The whole plan is rendered ineffectual if the buffer state fails to prevent or at least warn of a direct attack in force on the Wall, and catastrophic if this occurs during construction.
The building of Hadrian’s Wall 122-138
"Hadrian travelled through one province after another…. inspecting all the garrisons and forts. Some of these he removed to more desirable places, some he abolished, and he also established some new ones." [Cassius Dio 9.1].
In 122, when Hadrian and his court came to Britain, the garrison had been reinforced by the arrival of Legion VI along with the New Governor from Germany; Nepos, a close personal friend of the emperor.  These latter two events, particularly the appointment of Nepos, suggest that the decision to construct a permanent frontier had already been taken. 
In this first season an initial frontier was constructed from the bridgehead at Newcastle to the Cumbrian Coast comprising a standard timber rampart with a ditch in front.  Constructed by the army operating across the width of the country, and because this was effectively an extended fort perimeter with gates every mile and intervening turrets, typical of legionary field works, it could be accomplished relatively quickly.  This timber frontier was laid out to the same fixed scheme as the Stone Wall that was to replace it.  The route cuts more or less straight across the narrowest part of the country, along a line designed to take advantage of the spectacular escarpment of the Whin Sill.
Presumably, under the personal direction of the emperor, a series of elaborate forts, with three double gates opening north of the Wall, were laid out along the line, supplementing some of the existing ones from the earlier frontier. 
Work in this early phase was characterised by an abundance of unskilled labour evidenced by the digging of a construction trench for a frontier road, [The Vallum].  This was unnecessary, even counterproductive at this stage, unless there was a surplus of unskilled labour with nothing better to do towards the building of the Wall.  The excavation of a channel to divert the North Tyne at Chollerton in preparation for the building of the Bridge, as well as the digging of Wall foundation trenches considerably in advance of construction may also be part of this pattern.
In addition to the significant amount of planning and preparation work required for the replacement of the frontier in stone, a crucial logistical constraint was the availability of lime mortar.  The amount of dried fire wood required is equal to the weight of lime produced, so unless coal was used, there was a lead time to the production of mortar that takes the process into the next season [123] before building proper could start.  From then on, as sections of the stone frontier are completed, recycled wood from the timber rampart also becomes available for use as fuel or for building work.  
In this first season the army would have to build a series of more typical temporary forts to house the garrison and workforce close to the works, probably comprising a small camp every mile with larger camps reflecting the distribution of forts.
In 123 work on the Wall began in earnest with the army concentrated in the east along a 62km section, working on the complex aspects simultaneously, with aim of completing the Wall progressively in a westward direction.   Unlike the west, the eastern side of the country had abundant limestone, but it was also strategically stronger, being much better served by the navy and close to legionary hub at York.
In this second season, work on the most complex and time consuming tasks was prioritised, notably building the three bridges, three new forts, and the milecastles with their arched gateways.  The construction of the milecastles served to develop the logistic network, ensuring that quarrying and lime mortar production has to been established all along the route as far as the Bridge at Willowford.
The secondary priority was joining up these fixed units with a 10 feet thick curtain wall of mortared sandstone blocks on a pre-prepared foundation, known to have been organised around individual centuries. 
In this second season, the construction of a road did not progress, perhaps it was scheduled to start in year 3, but manpower could to be issue.  Just as it only makes sense to dig a foundation if there is a surplus of labour, similarly, only a shortage would prevent the next obvious step of completing the road in tandem with Wall, utilising the same resources.  It is the decisions around this aspect of the project are the key to what happened next.

Progress was halted, probably in the 124 season; it seems probable that there was a serious revolt in Southern England, evidenced by the destruction of Roman London, an intriguing spread of skulls in the area, the building of a new fort, and the sending of significant Legionary reinforcements from the continent. Whatever the army was doing, it was not progressing work on the Wall.
An analysis of the curtain Wall Logistics, suggests that the Romans suffered a significant loss of manpower, skills, and perhaps other logistical assets during the second part of Nepos governorship.  This resulted in a new plan under governor Germanus, abandoning or postponing the plan for the road and scaling back the Curtain Wall to 8’ or less.  Notably, the addition of three extra forts in the central sector strongly suggest the initial plan had left this area lightly defended relying on the topography of the Whin Sill escarpment and existing forts at Vindolanda and Carvoran .  The Wall was also extended from Newcastle to Wallsend, indicating that another potential weakness had been exposed.
However, this Narrow Wall plan was also never completed, so it is possible that both the eastward extension and the extra forts may reflect serious incursions from the North during the execution of this second plan.  
It is unclear how far work had progressed when Germanus was replaced by Severus, but it is known that he was reputedly Rome’s top general, because he was summon from Britain to deal with a serious revolt in Judea in 133. 
Progress was so slow that the timber rampart west of the fort Birdoswald, made of alder and hazel, and was too badly rotted be functional or recycled.  As a result new temporary ramparts were built to allow the work to continue on the Wall to the North of the Original line. 
Sisenna was the fourth Governor in charge of the project when Hadrian died in 138, but despite significant scaling back and the sending of additional troops progress towards the replacement of the frontier in stone had reached around roman mile 56 of 80.  The project seems to have met its ignominious end just 7 miles beyond where the army had been building their Broad Wall Bridge at Willowford 15 years earlier. 
An Imperfect Subjunctive Past
“… the first to construct a wall, eighty miles in length, which was to separate the barbarians from the Romans” [Historia Augusta].
This is the only significant reference to Hadrian’s Wall; it is hardly a celebration or ringing endorsement of a foreign policy triumph, and the Latin carries the implicit meaning that it failed in its purpose; {………., qui barbaros Romanosque divideret. }.
Hadrian had no doubt assumed that the population of Southern England would be prepared to participate by providing labour and other resources in addition to supporting the largest army of occupation in the empire. Presumably, the “Normal” distribution of this large garrison represented a response to existing security concerns.  
The stress on the labour supply has implications for the food production, something easily upset by external factors such as the weather.  However, the biggest risk is the actual project itself, which required the disposition of the army along a 73 mile frontier, in a manner best suited to the needs of construction.
One of the most frequent causes of military defeats is surprise, which almost by definition is being caught with your forces improperly disposed; [such as being ambushed while marching in column]. Geographically, it’s a position that can be easily outflanked by sea, and, as already noted, the entire strategy hinges on the allegiance and effectiveness of the buffer state to the north. Taking defensive position hands the initiative to the enemy, in particular the ability to concentrate at perceived points of weakness, which ironically, in this case, was probably the area, assumed to be most secure.
In addition, the project has the same logistical problems of supplying an army in the field, but without prospect of foraging supplies or booty as might be expected during a campaign.   The construction of a static line of defence combines most of the problems of campaigning with none of the advantages.
With the benefit of hindsight and in the light of subsequent modification, the plethora of gates would appear to have been a weakness, offering multiple potential breaches in the wall.  From Hadrian’s perspective, they must represent multiple places to counter-attack the enemy, since the strategic raison d'être has to assume there is time to pre-position sufficient forces to repel any attack. This reinforces the idea that the Wall can only conceivably serve any realistic military function as part of a wider political settlement involving the political allegiance and cooperation of the territory to the North.
Notably, the principle characteristic of subsequent development of the Wall, both in terms of the Milecastles and the Forts was the blocking of many of these gates.
Rationalising the irrational
“He personally viewed and investigated absolutely everything, not merely the usual appurtenances of camps, such as weapons, engines, trenches, ramparts and palisades, but also the private affairs of everyone, ……”[Cassius Dio 9.2]
Numbers only get you so far, in that engineering, particular military engineering is usually self-explanatory, and there is even an expectation of subtlety and ingenuity; but Hadrian’s Wall is dumb. Consider milecastle 39, on the top of the escarpment, with a set of gates opening onto precipitous drop, and it is obvious that Hadrian’s Wall is cookie cutter military architecture imposed on a landscape; it is an idea of a Wall; a back of the scroll sketch.
The multitude of gates is symptomatic of deeper problem about the design and execution of the project; this is not the work of a professional or competent commander in the field, but a simplistic and risky idea rigidly enforced by executive order.  The irrationality of the archaeological evidence can only be explained by seeking reasons in vagaries of Roman History, in particular the portrayal of Hadrian's character of in the two main biographical sources.
While, as emperors go, Hadrian was seen as a good bloke, a constitutional team player, he was also self-opinionated and more than a little contrary.  He had a high regard for own ability in all matters, certainly as it pertained to being Emperor and Commander-in-chief; he was hands on, nosy, meddlesome and got intimately involved in all aspects of military affairs. 
While it is easy to be drawn into the often prejudicial rabbit holes left by his biographers, Cassius Dio goes to some length to explain the story of Apollodorus, Trajan’s architect, who had Hadrian had banished and then killed.  Apparently, he criticised Hadrian’s knowledge of architecture in his youth, and then had been honest about the technical shortcomings of a design of a Temple proposed by the newly minted Emperor; this failure by a social inferior to take the opportunity to flatter the emperor was his downfall.
Thus, while Roman Senators like Hadrian were exceptionally well educated and uniquely experienced in administration, they were not all equally adept at adapting local talents to their needs.   Trajan did not fancy himself as an architect, and utilised professional talent like Apollodorus to design his bridges, whereas Hadrian would be tempted to do it himself, putting those involved in a difficult and potentially perilous position.
It almost feels like a stereotype; an arrogant emperor making sweeping decisions without adequate preparations, attention to detail and thought of consequences, but it almost exactly mirrors the criticism levelled against Hadrian by the unfortunate Apollodorus.
Pax Romana
Hadrian never returned to Britain, and the province hardly troubles his biographers further, and more generally only one episode clouds the otherwise sunny reputation of his reign.
In 130 Hadrian had visited Jerusalem, which had been destroyed by the Romans in 69, and decided to rebuild it as a Pagan Roman city;
"At Jerusalem Hadrian founded a city in place of the one which had been razed to the ground, naming it Aelia Capitolina…. This brought on a war of no slight importance nor of brief duration. . . . .
. . . . . . . . . . . . . .. . . . . .. . . . . . .   Few Jews survived. Fifty of their most important fortresses and 985 of their better-known villages were razed to the ground. 580,000 were killed…. As for the numbers who perished from starvation, disease, or fires, that was impossible to establish."   
Cassius Dio, The Roman History, 69.12.1, & 69.14.3
The reason for this digression is firstly, that it was the Governor Severus that Hadrian summoned from Britain to deal with this Revolt, and secondly, in a famous quote, an author likened the situation in Britain to the Jewish War documented above.
“... under the rule of your grandfather Hadrian what a number of soldiers were killed by the Jews, what a number by the Britons”
Marcus Cornelius Fronto, letter to Marcus Aurelius, AD162
This is the only direct reference to serious military losses in Britain, however, that the Romans suffered a significant loss of manpower, skills, and perhaps other assets during the project is evident from the numbers.  Only two thirds of the Hadrian’s Wall was ever built; despite being dramatically scaled back, what probably started as a 5 year project, was abandoned unfinished after 16 years by his successor.
The permanence of mortared stone construction is clearly a statement about the political solution this Wall represents; the Emperor had solved a troublesome problem in perpetuity, and made a statement about the limits of Roman territorial interest.   There is an eerie parallel, in that, two years after an imperial visit, the policy decisions taken have precipitated a crisis in the region; in both cases, Roman losses are hinted at, but in this case the response is documented.  For an emperor and 600 hundred of his peers to maintain control over 60 million people, no effort could be spared in punitive responses against sedition. 
Just to be clear; Hadrian was a Good Emperor, widely admired, he had respected the constitutional norms and very few of his fellow senators had died at his hands.  For his biographers, his reported killing of the architect Apollodorus of Damascus out of jealousy was regarded as a character flaw, and his genocide of the Jews was footnote in History.
Importantly, History has noted Hadrian’s complete self-confidence in his own abilities and knowledge in all matters, which combined with absolute military power, does much to explain the Wall.  Autocrats don’t have to admit they were wrong, and their contemporaries would be unwise to suggest it; it is clear that Hadrian blamed Nepos for the initial failure, and he never held office again.
More modern narratives of the Wall have stressed the idea of ‘dislocations’ or disruptions in the building program due to warfare, with Roman losses evident, although little thought has been given to the native population, or the role that this construction projects played in this cycle of violence.
End Game
The actions of the new emperor, Antoninus Pius, in reoccupying southern Scotland and building a new shorter wall across the Forth - Clyde Isthmus, tell us much about the failure of Hadrian’s frontier. It was considered preferable to build a new 63 km structure further north than complete the remaining 35 km; Hadrian’s Wall had not solved the problem, and the political alliance to the North had failed to protect his project. 
Like many extraordinary military adventures driven by the character of a commander in chief, ironically, it was probably Hadrian’s over-involvement that contributed to the failure of his own idea.
Notwithstanding the technical failings of the design, what remains of the Broad Wall attests to the logistical feasibility of the project, suggesting that this was a failure of politics not engineering.  Modelled as a logistical process, “building” the Wall was only the last stage in a series of labour intensive procedures which even with 3 legions and auxiliaries, would be unrealistic without significant additional manpower resources.   It is this unskilled labour that is harder to account for, but the failure of the plans has left a valuable snapshot in the archaeology, particularly the failure to complete a road clearly considered feasible at the outset.          
By the end of the century, some form of frontier Wall was functioning, although in very different circumstances; notably, most of the gates had been blocked.  More broadly, a tight grip was maintained over the Northern approaches to the Wall, and the vulnerable western flank along the Cumbrian Coast was consolidated.
However, one of most significant changes is the appearance of building inscriptions celebrating the contributions of corvée or civilian work parties, a marked change from the exclusively Military ones from Hadrian’s reign.   It would appear that by the end of the century, Hadrian’s vision of a Wall to “separate the barbarians from the Romans” had become politically relevant to the people living south of the Wall.  Thus, fifty years or more since Hadrian first imagined his Wall, one is actually finished as a complete stone border wall, and starts to function as we might imagine; this is the Wall that the tourists visit.
The North - South dynamic would remain a security issue for another 1500 years, and its politics persist today, reminding us that Hadrian’s border wall was a passing fad, a costly folly, which nevertheless successful fuelled the imagination of future generations in many unexpected ways.  


14 July, 2018

Understanding Hadrian's Wall at The Twice Brewed

There is a deep and abiding connection between archaeology and the pub, so it is appropriate that I should be giving a series of presentations in The Twice Brewed Inn; archaeology is coming home.
Understanding Hadrian’s Wall - a Mystery Solved 
A Free Presentation
5-6 pm Tuesdays & Thursdays
The Tap Room  
The Twice Brewed Inn, Bardon Mill, Hexham, 
NE47 7AN 
014346 344534
So this is an ideal opportunity for anyone interested in Hadrian’s Wall to go to a pub with its own Brewery, and as I understand it, an almost infinite supply of beer, although it’s best to book if you want sit-down dinner. Sadly, anyone wishing to base their summer holiday around this opportunity has probably missed the bus as they are fully booked.
It is an ideal venue to find people who have already made the not inconsiderable commitment to walking the Wall; while there is much to see and appreciate, visitors will find hard to get a coherent overview of this important World Heritage site.  Guide books will tell you about baths, barracks and where to find the naughty carvings, but will shy away from explaining the big picture for the simple reason there isn't one, at least one that is agreed upon or makes any sense in the real world. 
This is the best kept secret of the Wall; the academic community has no coherent explanation of what happened on this frontier during the reign of Hadrian.
Luckily, there is a local archaeologist on hand to help you understand The Wall, using computer modelling, engineering and soil science; the traditional Roman literary sources will still a mention, but it's surprising how much soil and how little Latin turns during an archaeological excavation.
Pro bono archaeology 
Giving a paper at a conference, one can take it as read that the participants know about the main pieces of the jigsaw and how they are currently arranged.
However, in explaining the Wall to anyone who is interested, it is easy to take local knowledge for granted, and forget to explain small but important ideas.   As a result, my 1st real slide is a Wall 101 which has been generated by points made and questions asked by previous participants.
However, the aim is a give an insight into the issues at the heart of Wall Studies, at a level that is normally only encountered at specialist academic conferences and postgraduate study.  I have also the particular problem of having to explain the Wall in terms the conventional academic narrative, ideas many people are not familiar with, – only to then debunk this framework point by point.  This is further complicated by the need to explain how we ended up with such a clearly dysfunctional set of ideas in first place.
Equally, you never know who you are going to meet in The Twice Brewed; it is a pub, so there is a risk you may encounter stray academics, so the research and its presentation has to better than what is currently sold to students or there would be little point in me turning up.
Realistically, what is being offered for free, has to be as good or better than what you are expected to pay for.  if you want to understand archaeology, ask an archaeologist; if you want to know how to teach, ask an academic.
It is important that students of the subject appreciate this difference; the ability to read and remembering is different process from thinking, it being the latter, that forms the key skill set of an archaeologist.  There is no reason why this subject need be complicated or difficult; inaccessible vocabulary and ideas represent either an inability to communicate or a lack anything substantive to convey.
Work in progress
 I spent much of a previous life training people in the use of specialist computer and telecommunications applications, sometimes it was the head of IT for a major corporation, sometimes it was someone just coming to terms with using The Mouse; in both cases the end product should be same, an appropriate understanding of the system.
The presentation is called Understanding Hadrian’s Wall, because the aim or outcome is an understanding, a resolution of a puzzle, hence a Mystery Solved.
From each interaction, I learning how to improve the presentation of these ideas, invariably adding information, which, usually, required the loss of something else or the production will reach feature length proportion.
Since my last encounter with academic system at the Reading the Wall conference at Newcastle, it was subsequently made clear to me nothing I produce will ever be accepted by a university.  If, 10 years ago they were prepared dismissed my work as worthless without the courtesy of reading it first, realistically, they are going to bothered now; incorporated engineering and soil science in my PhD was always going to put beyond the ken our new intellectually streamlined Universities.
Save ££££££ and £s
I have been working on a book. In my circumstances, it would be pointless producing to product designed to be sold to the students [which I am judged incapable of teaching] and I am not prepared to dumb down to a level where it compatible the existing commercial narrative.
Copying out other peoples research in your best handwriting is what is academics are for, archaeologists exist to recover and interpret data, converting soil and other materials into text so that scholars can understand it.
The problem that I have encountered during background research is that peer review is a meaningless concept in a subject like archaeology; its academic method can encourage the constant reproduction of fundamentally inaccurate information that undermines the credibility of many worthy aspects of the enquiry.
The presentations, which I started in May, have become an interactive way of developing a narrative structure to convey apparently complex ideas in an accessible and interesting way.
I would like to thank those who have already taken the time to attend and interact; this has proved a very positive feedback loop allowing me to continuously improve the presentation.
So, for just a little over an hour of your time, I can debunk for free an archaeological course that you would be charged hundreds, even thousands of pounds of real money for; Pro bono archaeology - why pay more?
Mystery Stories
Archaeology naturally lends its self to a mystery or detective narrative, which has the addition advantage of injecting a bit of tension and even jeopardy.
However, while it is difficult to sustain, it does allow for a cast of characters to introduced, the Romans, Hadrian, Nepos, the Natives, even the landscape, and you can present the existing narrative as the open and shut case put forward by the local constabulary in chapter 1, soon to be demolished by subsequent revelations.
The principle point of divergence from a detective narrative is the need to make viewer aware of their own preconceptions and expectations, rather than manipulating them in the interests of the plot.
There is a resolution, a mystery solved, but it is not a plot twist, and the coming revelation should be evident a long way off.  It involves a detailed examination of just three pieces of the puzzle, and ultimately debunks a couple of baseless [peer reviewed] myths, which is a generally positive contribution to knowledge, although it is clearly negative for those stakeholders with a commercial interest in merchandising the existing narrative, myths and all.
So that’s Tuesdays and Thursdays at The Twice Brewed, between 5 – 6pm; you are guaranteed a presentation of quality content not available anywhere else – for Free …. And there is beer and good food, what more could you ask for...

05 June, 2017

Hadrian’s Wall; milecastles, turrets and artillery

Problems; what problems? 
To the casual observer, what Hadrian’s Wall was for and how it worked is fairly straight forward, but dig a little deeper and all is not as it seems. 
If you accept the Wall as an exercise in military architecture and that warfare is ultimately about numbers, then the figures just don’t add up quite as you might expect.
 The “problem” is as much perceptual as academic, since it has long been patently obvious to serious study that the Wall “garrison” as represented by the milecastles and even the forts would be hard pressed to defend the wall in a conventional sense.  It would be fair to say that the Wall has been seen as much a base for counter-attacking the enemy as a barrier to be defended; with good early warning from outlying forts it was envisaged that decisive actions would have been to the north of the Wall.[1]
Thus, for reasons which I will discuss further below the way we view the Wall as physical barrier should not be taken for granted; I use the word “view” advisedly, since so little of the Wall survives, the way we “picture” the Wall, both objectively in its visual culture and subjectively in our own mind represents a “understanding” which profoundly influences our other forms of thinking.
My interest started with the proposition that the spacing of the milecastles and turrets at c. 540 yards [2] might be related to use artillery [balistas/ scorpio], which lead me to build a CAD model a model of milecastle, turret and connecting Wall.  I am now happy about the potential use of torsion bows, but other more widely accepted ideas expressed and illustrated in our visual culture of the Wall, do not make sense in terms of military architecture or strategy.
It is not a new problem, because it is the central issue of Hadrian’s Wall; put simply how was the Wall supposed to work in terms of military architecture?
The Plan
Leaving aside the subsequent changes, the initial plan for the “Broad Wall” was for curtain wall with gates every mile protected by a small fort or “milecastle”, with a garrison of about 40 -50, separated by two intervening small turrets.  By any standard this arrangement is lightly manned, and the classic model presumed that if attacked these garrisons would be reinforced from forts on or behind the wall [1], counter attacking via the many gates to trap the attacker against the Wall. The outlying forts on the major routes from the north would give warning to deploy troops to appropriate forward positions, particularly the main fighting legionary units of the army based to the south at York and Chester.
Thus, the Wall has been viewed more as base with the initial decision to punctuate the Wall with Gates every mile allowing complete freedom of movement into the areas north of the Wall.   The Wall provided a physical barrier that cannot readily be pulled down or burnt which would prevent horses, carts and to a lesser extent hostile troops crossing into the south; it was an expensive, but permanent solution. The only practical way through was to capture one of the gates controlled by a milecastle.
It is simply a question of force ratios; in convention military thinking the attacker needs a certain superiority of numbers in order to come a defended position, dependent on the nature of the position and the forces. 
Typically, attacker might require an advantage of 3:1 over the defender.
In this period Roman adversaries would deploy forces measures in tens of thousands, as Mons Graupius in 87 where Agricola faced 30,000 Caledonians.  While Roman forces fighting from defended positions were highly effective, garrisons of 40 or even 80 in the milecastle would be hard pressed if surprised by a force of thousands.   The chances of holding any mile of Wall even with reinforcements is hopelessly optimistic, given that anyone with a ladder could climb the Wall and envelope a milecastle.
The critical technology – the gates and associated tower, is well known and proven in Roman Fort which typically had four entrances, very different from Hillforts or castles.   Fortifications are entered and usually attacked via their gate, but the Fort by offering four possible places to attack, also forces the attacker to divide their forces to cover all the gates or risk being counter attacked by the garrison.
However, forts are a very different context; a typical legionary fortress like Caerleon has 4 gates and 30 turrets in curtain Wall perimeter of slightly over a mile in length; defended by a garrison of 4000 – 5000 of the best infantry.  Caesar describes how a Legion commanded by Cicero’s younger brother successfully held their fort against the Eburones uprising in the winter of 54–53 BC [3], [while a force of 15 cohorts who abandoned their camp were ambushed and massacred].
This is very different to the Wall, where Britain’s entire 3 legionary garrisons is only roughly equivalent to 180 men per mile or one every 30’; the curtain Wall is only defendable if you can get sufficient forces there fast enough.  Ultimately, it is the 10’ wide gaps in the Wall that are the key links in the chain, and the time taken by the enemy to capture a milecastle becomes the only important parameter.
Turrets as Artillery Platforms
The Roman’s use of torsion artillery was a unique capability in this theatre, which, given the small scale of garrisons, represents only realistic available methods of interdiction available from the milecastles or turrets. Thus, their spacing at roughly 540 yards could be related to the range of certain types of weapon.
Julius Caesar tells us of an incident where to prevent his troops being out flanked and enveloped by a larger force, Caesar creates, at right angles to his front, physical barriers covered by his artillery dug in at either end.
 “….on either side of that hill he drew a cross trench of about four hundred paces, and at the extremities of that trench built forts, and placed there his military engines…” [Caes. Gal.2.8]
What is significant here is distance between his artillery units, suggesting that some of his pieces had a range of 400 yards, which would allow mutual covering fire.
There is view that some engines had a range of up to c. 400 - 500 yards, which is supported by archaeological evidence from the Jewish wars. [4]  Excavation at Gamla besieged in 67AD  found that stone Balista shot of 2 -6 kg / 10 -16 cm was fired from positions 330 yards [300m] from town, shot being found up to 65 yards [60m] inside the defences.

The spacing of the turrets and milecastles at 540 yards is realistically too great provide mutual covering fire, however, while crossing the Wall in the middle between the turrets might seem the obvious choice for the attacker, it is the place is exposed to maximum crossfire.
Thus, in terms of artillery, the turrets were placed just far enough apart to be effective; by contrast sections of Caesar’s rampart at Alisia in 52bc, like the fort at Caerleon, had Turrets spaced every 27 yards, which is probably reflects the effective range of pilum in this context.

While artillery platforms are known from the area, [5], it has to be said that I am not aware of significant finds of bolts, stones, or other ammunition associated with the turrets or milecastles.   The argument might seem better if the towers were closer together, but it’s in keeping with general minimalistic approach to the layout of Wall.   

A Milecastle Model #1
Theoretical Structural Archaeology was developed for the complex problems presented by the foundations of timber buildings, but is equally applicable to the less ambiguous remains of stone walled structures. It attempts to model structures directly from the evidence of foundations,  independently of the visual culture or textual conventions of the period.  The engineering of buildings and other structures is governed by general rules, as well as the context specific conventions such as those found in military architecture.  In addressing the spatial evidence of the archaeological record it produces different results from research that simply considers the conventions of textual summery found in the Wall’s literary construct. 
Theoretical modelling, while not simulating the process of building, forces the modeller to take design decisions and follow through the consequences.  While it is possible to build a structure from individual randomised blocks, there is a law of diminishing returns, and any exercise in modelling is usually directed towards testing a specific idea or resolving a specific problem.
In this case, over and above an interest in the use of artillery, the model wished to consider general elevations of structures on Hadrian’s Wall in relation to how they were roofed.
The model is based on the plan of the Broad Wall Milecastle 48 at Poltross Burn and Turret 48A [6], with the very important proviso that the site is treated as flat rather than steeply sloping to the North as is the case at mc48.
The connecting Hadrian’s Wall and the curtain Wall are modelled in general terms without detailed consideration of the battlements and parapet, which although visually important, are less relevant to the model, representing optional detail.
Models and the diagrams they generate may be used to demonstrate a range of ideas that are contradictory or false, for this reason  Steve Oles from SketchUp, the software I used for this exercise, is included to reinforce the point that this is a form of scaled diagram used to illustrate an argument, and not an artistic representation.
Roofing is an important design consideration in structures with wooden floors traditionally a feature of buildings, although this not always reflected in the visual culture of the Wall.
Very roughly the structure occupies about 650 m² of which about 40% is the curtain wall and towers all of which is hard surface that has to be drained.
The model wished to test, rather than a pitched roof design, the use of a simple Mono-pitched roof for the internal buildings which can be extended to articulate with the curtain wall, which in principle has a number of advantages.
  • It would drain water away from the narrow spaces between the building and the wall, where there is no evidence of a drain.
  • In an Ideal arrangement the runoff from the majority of the structure is directed towards the drains of central roadway and out through the gate.
  • Protects the steps which are built around an earth core with a retaining wall which is best kept dry for stability; 
  • Facilitates a NW Kitchen based around the oven, [baking is traditionally an indoor activity]; 
  • Covering the SW and SE corners provides a latrine and perhaps some form of loose box; 
  • Provides a complete drainage solution for the whole structure.
The key parameter is the roof pitch; 30.5° / 7:12 was chosen as the lowest practical pitch for a pitched roof with wooden shingles which could be replaced by tiles; 8:12 or 9:12 would also be considered practical.
 The remains of steps comprising four partially surviving 11” x 8” steps and a 15’ 4” retaining Wall which argues for 12’ rise on the steps; the logic of the model would be to match this with roof pitch which might suggest 8:12.  In general terms, the steeper the roof, the taller the curtain wall in this arrangement, and vice versa.  

The basic building design has 4 separate rooms, which are shown with a central hearth, and although this is not certain for all rooms, it does imply a single storey infantry barracks.  The width of the doors also indicates there is absolutely no provision for cavalry, apart for the potential of space for loose box against the southern wall. 
There is no apparent differentiation in the design to indicate the presence of an officer, and no obvious implication to be drawn from there being 8 rooms; the century, basic component we are familiar with, is normally comprised of 10 units of 8 men. The rooms are smaller than those in typical infantry barracks; however, the latter represent the permanent residence of a unit, which may not be the case for milecastles. The precise garrison, usually put around 40-50, was presumably deemed sufficient to man the milecastle and the turrets on either side; defending the intervening stretches of Wall being impractical.
The gatehouses are shown with windows to light the internal spaces and provide additional firing positions; these a nominally based on utility and the presumed position of stairs, and doors for which there are fewer options. The roof shape chosen is a N/S oriented pitched roof, as opposed to an E/W orientation or pyramid form, the other simple contenders; while this arrangement was considered in terms of practicality, it also creates an appropriate architectural effect at the front of the structure.   
The Turret
As with the Gate house the point was to demonstrate the need for a roof given that structure would have had wooden floors and ladders or steps.
In addition to consideration of drainage, headroom required for weapons and protection from missiles is important.
In this case, a pitched or pyramid roof are the simplest options, combining the two can create more complex forms; in any event, a roof is required with a standardised form, reflecting the generally uniform nature of the structure.  Apart from the addition of a roof and artillery, this is general how these structures have been pictured.
There role has been seen as compatible with the similarly scaled small lookout and signally  timber towers evident in archaeology and art. [23]
One advantage of wooden towers is that achieving a 50’ high platform is relatively simple with the appropriate timber, which is significantly taller than the elevations envisaged for the turrets on Hadrian’s Wall.
Thus, the use of wooden super structure in addition to a basic roof, floors and fittings cannot be precluded to enhance the height, and hence effectiveness, of the turret.  However, the most significant issue encountered modelling a turret was it relationship the intervening Hadrian’s Wall.
One possibility is that a walkway was accessed from a door in the Turret, Logically, the turret would have had three doors, potentially making it more difficult to defend.
The alternative is that there is no direct access, which raises questions about the form of Wall and its relationship not only to Turrets, but also to milecastles.

Not unusually, having built the model, I am unhappy with various aspects; which is precisely why models are built. 
The initial idea about that the spacing of gate towers and turrets might reflect the use of torsion bow artillery, works reasonably well, although, perhaps in keeping with the general character of the linear frontier, it would represent a minimal use of resources.The effectiveness of artillery and observation would be enhanced by height, taller the better, as is the case with most fortifications.
The issue of the relative heights of the Wall and milecastle curtain  is the principle issue highlighted, but not resolved by the model. An "Ideal" section, illustrated above, might resolve this issue and perfect the drainage.
To get this to work, the height of the wall must relate to angle of the roof and its starting height; an additional complication is the steps, which I have had to recess into the wall it give some extra height, or face issues with headroom at the top.
As this is a military structure top roof should not be higher than the wall, and it would be ideal from a drainage point of view if the wall was just higher than the roof, so that the rapid runoff from the hard surfaces of the walkway had somewhere to go. The estimated height of the wall using the 4 surviving steps puts the walkway at 12’,[6], the model is about 15’.
What is concerning about the steps is that they are not bonded with the curtain wall, while this simplifies construction, at some point it must integrate with the bonded stonework, and for the curtain to have greater height a more complex design has to be envisaged.

However, the height of the wall is problematic in other respects, in particular in how it related to Hadrian’s Wall itself. If Hadrian’s Wall and the curtain wall of milecastle are the same height, then it possible to enter via the Wall, which given how easy it would be to climb, is a very insecure arrangement that does not altogether make sense.  
For Milecastles to function as a fortification with a secure perimeter, the curtain wall has to be higher than the Wall itself, which as we have already suggested would benefit the model for roofing the buildings, if mono-pitch rather than standard pitched roof design was used.  
However you look at it, there has to be some reasonable differentiation, some method of isolating the two aspects of the frontier; since defending one mile of Wall is impractical, it makes sense to raise the milecastle / lower the Wall.

Here again we return to the essential question of how the wall was supposed to work, and whether it can be assumed to have had a walkway with battlements. If so, how was this accessed from the ground, or from milecastles and turrets?
This question is complicated by the differing phases and standards of construction evident in what remains of the Wall, where distinguishing between normal and exceptional is not always easy.

The normal arrangement seen in forts like Chesters and Rudchester is that the Wall intersects at a gate tower. At Houseteads [above] and Greatchesters, where the Fort is inserted, the junction with Wall is marked by Turrets, which in sense is ambiguous, since we have to assume that these towers are higher than the curtain wall of the fort.  In these latter forts, and Birdoswald where both cases apply, the intersection of the Wall with corner turrets at an angle makes any provision for access unlikely.   
So while the arrangement in forts makes it clear that they a physically separate from the Wall, it does not shed any light on the same relationship for milecastles as the presence of turrets obscures any inference about the relative height of the curtain wall.   
Both milecastles and turrets in their Broad Wall form were built with similar 12’ “wing walls”, a stub of wall that facilitated a junction with the linear sections of walling built by different gangs that would join them up at a later date.
To some extent this restricts the likely height of Hadrian's Wall, since this is necessary to prevent a butt joint, an offset between the successive courses of the facing [like a flight of stairs]. 
For the sake of argument; if including mortar we a looking at standard 8” course of 12” blocks [7], then a 12’ wing wall is equivalent to 24 x regular 6” offsets, which at 8” per course, suggests a height of 16’; shortening the offset / block length would increase the estimated height. It is clear that precise height of any of the elements is difficult to calculate from the existing evidence, and that the separation evident in the forts sheds no direct light on the relationship between milecastles, turrets, and the Wall.
Given the crucial role of milecastle in maintaining the integrity of the frontier, I would be inclined to the view that that they must be physically separated from the Wall in order to maintain its perimeter.  This can be achieved by a height differential, or, perhaps, by building the Wall with a top that slopes on the inside and has no walkway.   
Thus, building a model to understand roofing, one of the main approaches to Theoretical Structural Archaeology, has taken an unexpected turn, which in this case, results in a reconsideration of underlying assumptions or presumptions, which is the point of deductive reasoning, and one of the advantage of evidence based model building.
Whether, the visual culture, and the expectation it has generated, could ever conceptualise a more simplistic and less elaborate form of Wall is an interesting question, but what is more important is to be able to distinguish between what derives from artistic or textual convention, and what is rooted in archaeological evidence.

Sources and Further Reading

[1] Handbook to The Roman Wall. J. Collingwood Bruce. Published by Hindson & Andrew Reid Ltd, Newcastle upon Tyne (1966) p.26
[2] op. cit. p. 22
[3] Caius Julius Caesar "De Bello Gallico" and Other Commentaries English translation by W. A. MacDevitt, introduction by Thomas De Quincey (1915) http://www.gutenberg.org/etext/10657
[4] Aviam, M., 2007, The Archaeological illumination of Josephus; in Making History: Josephus And Historical Method, edited by Zuleika Rodgers,  pp. 354 -355,  361-2, 381.
[5] eg.  High Rochester; https://en.wikipedia.org/wiki/Bremenium
[6] Gibson, J.P. & Simpson, F.G. 1911. "The Milecastle on the Wall of Hadrian at the Poltross Burn"; Trans. CWAAS XI (New Series) Art XXIII pp390–461
[7] Handbook to The Roman Wall. J. Collingwood Bruce. Published by Hindson & Andrew Reid Ltd, Newcastle upon Tyne (1966) p.33