The far east

The episode title of this section of the Roman Rock Trail isn’t perfect – as we are starting in west Durham in a place called Lanchester, then returning to the Wall at Heddon – a village which owes its position to its hard sandstone bedrock resisting glacial erosion more than the surrounding area. And then onto Benwell. A place not on the current Hadrian’s Wall Trail but from what I hear it will be in the near future. As will the final stop, South Shields Fort – popularly known as Arbeia. On the way we will look at Roman water engineering and perhaps iron production, examine some well exposed sandstone, delve more into the mysteries of the exploitation of coal and finish with a more obscure use of rocks – pigments.

Transcript

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Episode seven The Far East Like buses, there hasn't been one for ages, and then two come together. I'm trying to make up for the gap in the podcasts. The episode title of this section of the Roman Rock Trail isn't perfect, as we are starting in West Durham, in a place called Lanchester, and then returning to the wall at Hedden, a village which owes its position to its hard sandstone bedrock, resisting glacial erosion more than the surrounding area at any rate. And then we're off to Benwell, a place not on the current Hadrian's Wall Trail, but from what I hear it will be in the near future. As a final stop, South Shields Fort, popularly known as Arbeir. On the way we will look at Roman water engineering and perhaps iron production, examine some well exposed sandstone, delve more into the mysteries of the exploitation of coal, and finish with a more obscure use of rocks. Pigments. Just west of Lanchester is a Roman fort, Longovicum. Supplying the fort with water was a network of aqueducts and dams, testimony to the skills of Roman engineers and their understanding of the landscape. To build such infrastructure today would require a multidisciplinary team. The design, plan, calculations and installations would need civil, geotechnical and mechanical engineers. Understanding the shape of the site, the rocks and the water dynamics, and where the dam materials would come from is the work of surveyors, hydrologists and geologists. The Romans had all of these skills within their legions, but they were not working from scratch. A comprehensive range of specifications had been devised by engineers like Vitruvius in the first century BC. When the Reverend John Hodgson, curate of Lanchester, and an antiquarian, saw them in 1805, the series of aqueducts and dams in the valleys west of the fort were, in his words, as visible as the day they were made. His investigations were published in Archaeologia Aliana, the journal of the Society of Antiquaries of Newcastle upon Tyne he helped to found. One hundred and thirty years later, when another giant of archaeology, Kenneth Steer, explored the structures as part of his PhD, they were evident, but much less apparent. Subsequent damage by agriculture, forestry and coal extraction means that the aqueducts have all but disappeared, but the dam can still be clearly seen. The Roman engineering starts five kilometers west of the fort in a small valley of the Dyke Nookburn. This valley, possibly a glacial meltwater channel, is cut into carboniferous rocks, sandstones and shales containing two significant layers, the Brockwell Coal and the German band ironstone. These two rock units also occur near Longovicum Fort, and were exploited extensively from the sixteenth century and perhaps long before. The dam site was surveyed in detail, most recently in the nineteen eighties, by a local civil engineer. He recorded it as around six meters wide and a hundred meters long. In plan it is a curve, a sideways arch with a radius of forty five degrees, convex upstream. The survey noted the remains of the stone block facing, and that the core was a clay base with sand above. They speculated that it must be one of the earliest ever arched dams. Open channels, aqueducts, connected this dam with another, and then with a series of aqueducts it carried water to the fort. At one point one of the aqueducts must climb uphill. The hypothetical solution to this obstacle, suggested by Kenneth Steer, was a siphon system using lead pipework. The Romans had used these elsewhere. Why did the Romans build such complex structures to supply so much water? It seems excessive for the usual domestic and bathing water needs of a fort. Could the reason be that, with local coal and iron ore available, water was the third essential ingredient needed to smelt iron? The Reverend Hodson also recorded thousands of tons of slag in the area, and numerous hearths, cinders and slaking troughs around the fort. From Newcastle to the crossing of the river North Tyne, the wall was built in long, straight lengths in stone, adjusting its direction on hilltops. What, if any influence did geology have on this eastern sector of the frontier? The terrain here is very different to that of the central windsill sector. The bedrock here, layers of sandstone, mudstone and limestone, tilt more to the east than the south, and the resistant windsill swings away northeastwards. Just west of Hedden, the wall crosses the dividing line between the older Carboniferous rocks and the younger rocks of the southeast Northumberland coalfield. This division is based on fossils and a progressive change from open sea to coastal swampland which produced abundant coal seams. The change cannot really be recognised in the rocks at surface, but from here on eastwards the evidence of the last three centuries of coal mining gives it away, even today. But three hundred and twenty million year old bedrock is not the only influence on the landscape here. A much more recent geological event shaped this land too. Only twenty thousand years ago a seven hundred meter thick ice sheet flowed eastwards, sculpting the rocks beneath it. The glacial debris it left behind smoothed out the terrain even further. The imprint of the last glaciation here is west east. Ridges, resistant low sandstone hills peeping through a thin covering of stony clay, plastered unevenly along across this undulating landscape. The line the Roman wall planners chose used those high, dry ridges, all the while trying to maintain a view into the valley of the Tyne. Benwell, Hedden, Eppies Hill and Harlow Hill are just four of these higher places, each one underlain by sandstones, two of which have been quarried, at least in post Roman times. In Hedden Village, sandstone is exposed beside the line of the frontier, and a little further east over two hundred meters of the wall in its ditch are visible. This fragment is one of the best preserved sections of the originally specified broad wall. It had a theoretical width of ten Roman feet, that's about three meters. Soon after its building in AD one hundred two, one hundred two three, the specification changed and the thickness of the wall was reduced to narrow gauge, around two point two metres. A thinner wall would speed up construction and was synchronous with the decision to place twelve forts and more than six thousand men along the frontier. One hundred years ago a section of the wall rebuilt by Severus at the Great Hill in Hedden was excavated, so a new road could be built. The core of the foundation level between large quarter ton sandstone blocks was cemented stone rubble, set so hard it had to be blasted out. Another Roman rock recipe concrete. The northeast of England is synonymous with coal, but the working of coal by the Romans here still has its uncertainties. Where did they extract it? And what did they use it for? Benwell, a suburb of Newcastle with a Roman fort, provides us with more clues. Coal is dead plant matter that was turned into a rock by millions of years of heat and pressure. Around three hundred and ten million years ago, in the later Carboniferous period, the environment of this piece of northern England was tropical swampland, lazy rivers and lagoons. The plants in the swamps died, and the resulting peat layers were buried under sand and mud, ultimately becoming coal seams. Beneath the Roman fort at Benwell, known as Condicum, are some of the twenty to thirty seams that form the world-renowned Northumberland and Durham coal field. At the surface, on the valley side, 300 meters south of the fort, is the thickest of those coals, the two meter high high main seam. Did the Romans work and use coal? Definitely, yes. There is evidence from many hundreds of places across Britain. Unfortunately, as the Roman word for coal, carbo is also used for charcoal and wood, references in most historical literature may be ambiguous, and that can complicate things. Did the Romans actually mine it here at Benwell? A 2017 excavation within the civilian settlement, known as Avicus, south of the fort, located a building containing a large amount of coal. An earlier archaeological excavation had retrieved coal fragments which had fossil spore and chemical affinities with a seam which occurs beneath the site. Antiquarians from the 16th to the 19th centuries believed that the shafts and bell pits they excavated on the site were Roman, but others, including mining specialists, regarded this historical evidence as inexpert and equivocal, and attributed the mine workings to medieval or later times, suggesting the Romans merely worked surface exposures of coal and not much of it at that. As with other minerals, archaeological evidence of extraction is often speculative, because any subsequent workings will have removed all trace of Roman ones. From the evidence we have, the Roman military used coal all along the wall, and it is probable that it was also being transported some distance, to the Thames and the Fens, which would imply its widespread use and a very organized distribution operation. The assumption is that the major use of coal was for warmth, for cooking and metallurgy, but there is evidence of its likely use in drying grain, the manufacture of ceramics and brine evaporation, and even for cremation and jewellery. It is possible that other fuel sources, wood and charcoal, were unable to cope with increasing energy demands, especially in distant places whose populations were growing. Regrettably, coal, one of the few minerals we can trace the provenance of well, is often disregarded, misidentified, or not probably recorded in archaeological excavations. If, in future, digs record the detailed context of coal and submit it for analysis, then we stand to learn more about the use and origin of a key Roman energy resource and the sociopolitical stories it can tell. South Shield's Fort is popularly known as Arbea, the Fort of the Arabs, from Mesopotamia. But that name is disputed, so I'll stick with South Shield's Fort. The scale and grandeur of Hadrian's frontier is extraordinary, but it is sometimes difficult to imagine it as it was one thousand nine hundred years ago. South Shield's Fort gives us an insight. Even those of us who are passionate about the wall monuments acknowledge that it isn't easy to translate the grey brown stones of its skeleton into the living landscape it used to be. But these Roman buildings have not always been the truncated, muted remains you see today. Many were covered in white lime render and painted in a variety of colours. While South Shield's fort has attracted controversy in archaeological circles, for most visitors, the full size reconstruction of the buildings and interiors will bring the frontier to life. The size of the rooms and the height of the ceilings in the late Roman courtyard house are a surprise. But it is the walls, with their interpretation of fresco painted patterns and motifs, that may be the biggest challenge to preconceptions of Roman life here at the edge of the Empire. Vibrant colours are not something we associate with the wall and its monuments, and yet painted plaster fragments from South Shield's Fort and villas in southern England show they were used. Only recently the excavation at the Cricket Club in Carlisle has encountered similar painted plaster walls, often with multiple layers of paint. The dull sandstone and Watland Daub walls were plastered with white lime render, made by burning local limestone in kilns and mixing the resulting quick lime with water. Several layers may have been applied, and the internal surfaces of walls in high status buildings may have been built up with finer coats before finishing with whitewash. The painted patterns and motifs, frequently shades of reds and orange browns, were produced from natural pigments. Some were undoubtedly plant based, but others were extracted from rocks. Ochre and umber are derived from iron minerals within iron rich rocks like ironstones and red sandstones, or from mineral veins and their weathered residues. All of these are common across our region, and quantities of umber and ochre were still being mined near Alston around one hundred and forty years ago. Green and especially blue pigments are rare, and some may have origins in copper minerals like malachite and azurite, both of which are found in the north of England. White pigments were produced from limestone, gypsum and lead, all in abundance locally. Pigments were not just used on walls, they have been found colouring inscriptions on altars and were used for dyes, cosmetics, and even medicines. Geochemical analysis that might help distinguish between local and imported pigments is expensive, and so it's rarely done. And so, like in Taglios telling stories about their origin and trade, we must wait. Sadly that's the end of the Roman Rock Trail, and the third series. We've visited twenty eight places on our journey along the frontier, from the Irish Sea to the North Sea. Such a short distance between the two seas, always a great reminder of what a small island nation we are. There are many, many more places, certainly more than the other twenty two in the rocks at the edge of the Empire book, that's for sure. Those fifty sites in the book try to make the connections between rock and romance, but they are just a small selection of the places you could discover if you choose to travel along the edge of Hadrian's Empire. I hope you will come and explore it. What's next for the podcast? Well in my head for the coming series are more trips, but this time along rivers, tracing rocks and their influences down the courses of the four major river valleys in the north. How does that sound?