Saturday, 3 November 2012

Viking Weights: Part 1

The lead weights with metal insets discussed below were rough and ready tools for weighing bullion in a metal-weight economy. The Vikings also had access to more regular, standardised weights in iron and copper-alloy, which were manufactured to specific weight units.

Oblate spheroid weight from Yorkshire, recorded by the PAS
(PAS 'Find-ID' YORYM-01C134). The copper-alloy shell has corroded,
revealing the weight's iron core. Image courtesy of the PAS
One type of standardised weight is known as the oblate spheroid: a spherical weight with flattened poles with an iron core and copper-alloy shell.  These weights originated in the Arab Middle East. Unlike the lead weights, they were made in accordance with the official Islamic weight standard, the mitqāl, of c 4.23g. It's for this reason, as well as the fact that they were difficult to forge, that they're often described as 'regulated' or 'standardised'.

Oblate spheroids first arrived in Scandinavia during the late ninth century, along with large numbers of Islamic silver coins known as dirhams. They are thus closely associated with the weighing of silver as payment: a connection supported by the fact that some silver hoards from Scandinavia contain oblate-spheroid weights.

Interestingly, these weights are also found in England. They must represent imports from Scandinavia, and are thus firmly associated with Viking activity. Yet their distribution shows some unexpected trends. Whereas we might expect the weight distribution to be correlated with that of Viking-Age silver hoards, oblate-spheroids in fact show a different geographical pattern, focused mainly in the east of England, although with some overlap with hoards in Yorkshire. A significant number of examples come from East Anglia, where there are no certain Viking hoards.

Oblate spheroid weights (clear circles) vs hoards (black dots). Copyright J Kershaw.

In this map, the black dots represent hoards (e.g. Cuerdale; the Vale of York), and the clear circles oblate-spheroid weights. This shows the 40+ examples I've recorded from England (excluding the Viking winter camp sites of Torksey, Lincolnshire, and 'A Riverine Site near York').  Others are also known from Scotland and Viking Dublin. Since oblate-spheroids vary in weight (typically from c 8 to several dozen grams), I've increased the size of the circle in line with the weight: the heavier the weight, the larger the circle. This will, I hope, give a sense of differences in the quantity of silver being exchanged across regions. The map shows that even in areas which minted coins under Viking kings (e.g. East Anglia; York), a vibrant bullion economy operated at a variety of levels.

I've found this a useful way of visualising the hundreds of single finds of bullion and bullion-related items I've now recorded a part of my project.  By combining this data with that from other artefact groups, such as silver ingots and rings, I intend to test this apparent disconnect between the distribution of hoards and single finds of bullion, and to plot the distributions against regional levels of metal-detecting activity.

Feedback on this, or other approaches, is always welcome!