Iron Age Inverness

Philip Dunshea writes: 

News in from Inverness, in what later became northern Pictland, where archaeologists have unearthed evidence for iron-smelting and iron-working in a late prehistoric context.

Iron was a valuable and coveted product in medieval and pre-medieval Scotland; by way of illustration, there is a classic ‘dog-in-a-manger’ anecdote from the end of the first century A.D., when the Romans were grappling with the issue of what to do with the recalcitrant peoples of the Highlands. In the wake of the famous battle at Mons Graupius, Agricola and his troops built a 22-hectare legionary fortress at Inchtuthil, near present-day Blairgowrie, on the hinge between Strathmore and Strath Tay. But the site was abandoned a few years later, seemingly in a hurry, and ten tons of iron, including over a million nails, were buried in a deep pit inside the fort. Clearly the departing troops lacked the time or the means to transport such an impressive stockpile away with them, but were under strict instructions not to let any of it fall into the wrong hands.

But then the natives were also quite capable of making the stuff for themselves, and had been doing so for many centuries. At Beechwood Farm to the east of Inverness, where new buildings for the University of the Highlands and Islands are under construction, archaeologists have come across the remains of an ironworking hearth, an early form of the ‘bloomery’ used to smelt iron before the invention of the blast-furnace. The structure is surrounded by deposits of slag, the waste-product formed at various stages of smelting and smithing. Its discovery marks another contribution to our understanding of how society and economy operated around the Moray Firth, one of the crucibles of Scotland’s pre-history.

Map of the Moray Firth, © Wikipedia Commons

Power was visibly concentrated in this corner of Scotland in the early-historic period: forts like the massive enclosed promontory at Burghead, and later monasteries such as the celebrated foundation at Portmahomack on Tarbat Ness, speak of a society ruled over by potentates with extensive command of resources and populations. This ‘landscape of power’ can be traced in various manifestations until the onset of the Viking Age: the lands around the Moray Firth have one of the highest concentrations of Pictish sculpture in the whole country, and if we take Adomnán’s Life of Columba at face-value, it was from here that king Bridei ruled over a wide hegemony in the mid-sixth century. Bridei’s ‘capital’ may have been located at the hillfort on Craig Phadrig, just to the west of modern Inverness. When the region finally emerges in the slight documentary evidence for the seventh and eighth centuries, it is under the name of Fortriu – of all the divisions in the murky political landscape of Pictland, it is by far the best attested.

All this must have entailed resource control, principally in terms of agricultural produce and livestock. But over the last decade or so it has become increasingly clear that the lands at the north-eastern end of the Great Glen were also home to a number of centres for proto-industrial activity. There was a major hub for iron production at Culduthel, to the south of the city, where among a cluster of roundhouses many of the structures were found to contain hearths similar to that unearthed at Beechwood, their floors fused with a crust of iron slag.  Nearly two hundred finished iron artefacts – mostly weapons and tools for working wood, leather or metal – were recovered from the site, along with a quarter metric tonne of iron slag.

At another site at Dornoch, thirty or so miles to the north, similar activity continued into the viking period and beyond (a new forge was erected there as late as the fifteenth century). But the sequence is now being extended further back as well. There is a bloomery furnace near Forres dated to between 400 B.C. and 100 A.D. Carbon-dates provided so far at Beechwood Farm suggest that smelting activity took place between 400 and 100 B.C. – that is, in the pre-Roman Iron Age.  In this respect, the cumulative impression is one of considerable economic continuity in the region.

All of this begs the question of where the iron ore came from (the only other raw ingredients needed for ‘bloomery’ smelting are wood to burn, and a good water supply). The Romans had plenty of iron mines in Britain, and most of their ore came from the Weald of Kent and the Forest of Dean. As for Scotland beyond the limits of empire, there are (or were) rich deposits of iron ore – on the island of Raasay, for instance, over on the west coast. Haematite and magnetite is found in small concentrations in the older schist and gneiss rocks of Skye, Shetland and Kishorn. None of these are known to have been mined before the seventeenth century, however, and it is thought that virtually all of the iron smelted in earlier times was produced from a regenerative source called ‘bog iron’. This typically forms where iron-bearing ground water rises to the surface, where (possibly aided by bacteria) an oxidised crust of iron ore forms. After ‘harvesting’ the crust can reform within as little as two decades – a superb example of a renewable resource being exploited in a proto-industrial context.

Formation of Bog Iron, photograph © United States Geological Survey Commons

Elsewhere in Scotland, there is a definite link between metal-working and aristocratic (or even royal) status in the early historic period, for example at Dunadd, in Argyll, or at Whithorn and the Mote of Mark in far-off Galloway. Jewellery manufacture, at any rate, and other forms of advanced metal work, were the preserve of the elite (including the clergy) and the craftsmen they controlled. Smelting presumably took place in situ, with the traces usually found nearby. The earlier examples in Moray are in some respects no different: the Culduthel furnaces surround one of the largest roundhouses ever found in Scotland, twenty meters in diameter, and there is evidence at the site for prestige activities like glass production and bronze-working. But there are also signs, at Dornoch, that iron smelting sometimes took place in a rather cosy domestic context, perhaps little separated from the supply and preparation of food. How the Beechwood furnace fits into this wider picture remains to be seen.