Introduction

Salt is a mineral resource essential for the existence of human societies, and crucially, one that must be procured in part through artificial means. It may be obtained directly by mining deposits accessible from the surface, a technique which was used during the Bronze and

Iron Ages at the sites of Hallstatt and Hallein in Austria, or extracted from sea water sources through simple evaporation. This technique, still used today to produce salt along the Atlantic and Mediterranean coasts, was also used in these same areas in the ancient and medieval periods where salt marshes were managed in such a way to produce sea salt of varying qualities. Thirdly, evaporation can be forced in various types of furnaces, the brine being obtained from saline springs or by washing sediments or plants containing salt. This technique (poeles a sel or boiling brine) was used extensively in the medieval and modern periods, and also during the protohistoric periods in Europe and is recognisable through its waste products of broken pottery containers, or briquetage.

Of these three techniques it was the practice of boiling brine that was used most extensively during European prehistory, or in any case the one which has left the most discernible archaeological evidence in the form of briquetage. The oldest archaeological evidence for boiling salt dates to the Neolithic era, roughly the fourth millennium BC, from the Lengyel Culture in Poland. Archaeological evidence of salt extraction dating to the first half of the sixth millennium BC has, however, recently been discovered in the French Alps in Moriez (Morin 2003). The techniques associated with briquetage spread primarily during the Bronze Age throughout Europe. However, it is during the Iron Age that the extraction of salt through boiling brine and its further refinement into ingots, all within specifically designed furnaces, reached its maximum extent (Figure 1). A series of inland salt springs in Lorraine (France) and Baden-Wurtemberg and Hesse (Germany) are the principal known centres for salt production in Europe and were intensively exploited. In contrast to the above relatively large centres exploiting salt springs and mines, along the coasts of the Atlantic and the North Sea the number of small workshops exploiting salt marshes and salt derived from sea water increased in particular during the late La Tene period (Saile 2000; Fries-Knoblach 2001).

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The Briquetage de la Seille: location and brief history of research

Remains of one of the most significant Iron Age salt extraction and production centres in Europe are located at Briquetage de la Seille, in Lorraine, eastern France ('Haute Seille' on Figure 1). A series of workshops, located around numerous brine springs, spreads across an area roughly 10km by 3km. Located within the valley of the Seille River (Moselle), the volume of waste produced from salt production activities, which is evidenced by fragments of salt moulds and the remains of earthen furnaces, totals roughly 4 million cubic metres. The broken and discarded furnaces and moulds form gigantic mounds that range from 1 to 12 metres in height and 50 to 500 metres in diameter. So great were, and indeed are, these mounds, that the Roman and then medieval urban centres of Marsal, Moyenvic and Vic-sur-Seille were built upon them.

At the end of the seventeenth century, the Kingdom of France fortified Marsal and Moyenvic to protect its still profitable salt production industry. There, the royal engineer Royer Arteze de la Sauvagere observed and noted the presence of significant accumulations of burnt earth (Figure 2) that he named 'briquetage' (de la Sauvagere 1740). During the nineteenth century the function of these over-sized mounds remained enigmatic, with their creation sometimes attributed to the Franks (Dupre 1829), to the Celts of the time of the Roman conquest (Beaulieu 1840-1843), or even to the Late Palaeolithic period, or Age du Renne (Ancelon 1870).

[FIGURE 2 OMITTED]

With the start of large-scale excavations conducted by the new German conservator of the Museum of Metz at the beginning of the twentieth century, progress was first made in relating the Briquetage de la Seille to the extraction and production of salt (Keune 1901; Beaupre 1901); indeed this was the first research which linked the briquetage or terracotta elements to the specific activity of making salt by boiling brine. It is also these first systematic excavations which contributed the term 'briquetage' to the archaeological lexicon, which is now in use throughout Europe.

New research at Briquetage de la Seille

In the 1970s, after a break of more than 60 years, new research was initiated under the direction of Jean-Paul Bertaux, archaeologist with the Archaeological Service of Lorraine (Service Regionale a'Archeologie de Lorraine). Conducted over ten years, the main contribution of the project was the identification and basic recording of the principal accumulations of briquetage within the Seille valley, and the development of the first typology of the technical elements, especially the salt moulds, associated with briquetage (Bertaux 1972a, 1972b, 1976). In 2001, a new international research project on the Briquetage de la Seille began, aimed at determining the spatial and chronological organisation of the Iron Age workshops within the valley extracting and producing salt. The research also aims to understand the environmental and social impact of exploiting this essential resource in what is obviously a developing proto-industry in the Seille valley (Olivier 2001).

Because of the vast scale of the study area a variety of investigative techniques have been employed, including geophysical remote sensing, sediment coring, test trenching, field walking and open-plan excavation. Surveying an area of roughly 58 square kilometres by multi-frequency electromagnetism (EM) from a helicopter made it possible to create a three-dimensional survey of geological formations 20 to 40 metres below the current ground surface, and, crucially, to determine the process by which local ground water was increasing its salt charge, mainly through the dissolution of rock salt formations located between 50 and 150 metres below the surface (Bourgeois et al. 2003). Combined with a magnetic survey (MAG), the electromagnetic survey showed that significant and substantial accumulations of briquetage are located at the modern villages of Moyenvic and Marsal.

Fluxgate gradiometry permitted the identification of a vast zone of workshops in the Pransieu and Fort d'Orleans areas around Marsal. Alignments of furnace agglomerations, which extend in some cases over several hundred metres, are the most prevalent features and are located and organised along the sides of a newly identified palaeo-channel of the Seille (Figure 3). Excavations showed that the furnace agglomerations are indeed made of individual, approximately two-by-three metre, U-shaped furnaces (Figure 4). While Bertaux believed the U-shaped furnaces were used to fire the ceramic vessels themselves, work conducted during the 2003 and 2004 seasons indicates, conversely, that brine would be placed in already fired large flat-bottomed ceramic containers with individual capacities estimated to be somewhere between 20 and 50 litres, with these containers placed on top of the furnace for boiling. Initial test excavations recovered substantial amounts of charcoal allowing radiocarbon dating of these structures to the Hallstatt period (Ha C-D 1 or seventh to sixth centuries BC). Domestic ceramics from contexts associated with the furnaces confirm the early Iron Age/Hallstatt C-D 1 dating.

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Prehistoric salt extraction in the Upper Seille Valley: chronology and extent

The waste products that we know today as the Briquetage de la Seille were created primarily by salt working activities in the Iron Age. Two principal phases of activity can be distinguished: the first, or old phase, dates from the early Iron Age, between the eighth and sixth centuries BC. The second or recent phase dates from the end of the late Iron Age, between the second and first centuries BC. The production of salt using methods specifically associated with briquetage ceases with Romanisation, probably during the first century AD.

During the early Iron Age, workshops are distributed between ten or so production sites, undoubtedly located in the immediate vicinity of the principal salt springs within the valley (Figure 5). These production sites, which in general cover areas between one and four hectares, consist of workshops where salt-boiling furnaces, zones of waste disposal and a salt-water source are tightly associated. Indications that domestic activities took place within these same workshop areas are frequent, consisting mainly of fragments of domestic ceramics and faunal remains, many of which show signs of butchering.

[FIGURE 5 OMITTED]

During the second phase of salt production within the study area, significant re-structuring took place, with production concentrated at and around three major centres: Moyenvic, Marsal and Vic-sur-Seille (Figure 5). The extent of the waste accumulations associated with the new centralised production of salt also signals a shift in the scale of production; from areas of a few hectares covered during the early Iron Age, to area in excess of 10 hectares at the more recent late Iron Age centres of Marsal and Moyenvic (the extent of the debris at Vic-sur-Seille is at the moment only partially known). It is upon these islands of what can only be termed 'industrial waste' that the Romans developed their urban centres of Marosallum (Marsal), Vicus Bodatius (Vic-sur-Seille) and Medianus Vicus (Moyenvic). The production of salt, as noted within the study area, was confined to these three centres in the first half of the first century AD, and through the medieval and modern periods.

The technology of salt extraction

The production of salt within the Seille valley was a two-stage process: the brine extracted from the springs or wells (both likely being managed water sources) was heated over furnaces in large ceramic basins, the product being a salt paste. The second stage was to condition this paste into a form of ingot. The production of salt ingots required a second type of furnace comprising partially fired clay 'bars' joined into a grid with fresh clay buttons (elements de liaison in the terminology of the project). The purpose of the grid was to support the salt moulds holding the salt paste for final firing.

In the second industrial phase, at the end of the early Iron Age (during the La Tene period), the techniques were modified, apparently with a view to improving efficiency (Olivier 2001 : 160-161). The moulds became very uniform suggesting that they are directly produced on wooden forms in sizes relating to small ingots. If this is indeed the case then large numbers of moulds can be made very quickly, with the moulds a uniform size resulting in a uniform, more currency-like, product. More importantly, the scale of production also changes. It is estimated that during the early Iron Age the amount of salt produced may have been in the hundreds to thousands of tons per annum; but during the late Iron Age, between the second and first centuries BC, the amount of salt produced is likely to have been in the thousands to tens of thousands of tons per annum. It is during this phase of activity that the character of salt production within the Seille valley attained what can only be considered a proto-industrial scale. Not only did production levels exceed what might be considered necessary within a local framework, but the production activities also clearly indicate from this point onwards a specialist activity.

Social and environmental impact of the Briquetage de la Seille

The early results of our investigations into the Briquetage de la Seille suggest that in social terms substantial wealth was generated during the early phase of the Hallstatt period, especially towards the end of the sixth century BC. At other major salt producing sites (Hallstatt, Hallein, etc.) burial evidence suggests that people connected with extracting salt generated relatively large amounts of personal wealth when compared to their non-mining compatriots (Hausler 1968; Hodson 1990). While we do not know if the richest graves of the Hallstatt cemetery directly belong to the miners, we can conclude that the Hallstatt cemetery is the only one, within the entire Hallstatt culture area at least, to display substantial wealth directly related to salt mines. By analogy, salt producers at the Briquetage de la Seille could have generated high relative levels of personal wealth. There is some evidence that they did, in the form of pieces of coral and amber recovered from waste deposits. Coral is known to be part of a late sixth century specialised craft activity usually found in direct association with the late Hallstatt 'princely sites' (see Champion 1985). However, these appear to be pieces of raw material yet to be transformed into jewellery inlay by specialised crafts-people, suggesting that specialised workshops, other than those for salt making, were associated or even located within the salt making sites.

There was some variation in the association of wealth indicators with each phase. It appears that during the early phase of the Briquetage (Late Hallstatt period) the salt producers were probably relatively wealthy, while in the later La Tene phase, which is associated with more centralised industrial activities, there is no particular evidence of wealth in the settlement. This suggests that in this later phase of industrialisation the wealth generated by salt production was diverted elsewhere, perhaps to individuals controlling its distribution.

Perspectives: a proto-industrial activity

Making salt during the Iron Age in the Briquetage de la Seille was an intensive activity--more akin to an industry than a craft. Modes of production were specialised: there were areas for boiling the brine, other areas for baking the salt ingots and other areas for discarding production waste. The layout implies a demarcated organisation of labour: there were probably different teams of people making elements or pieces of briquetage, others boiling the brine, others drying the salt into ingots, and still others organising and transporting the salt across Europe.

Distinguished by its scale of production (as well as the scale of its remains), the Briquetage de la Seille well merits the term 'industrial' during the Iron Age, and it seems probable that at least during the later phases of production at the centres of Marsal, Moyenvic and Vicsur-Seille, it employed some form of division of labour alongside the development of more efficient means of production. At this point also the resulting wealth may have passed to the owners rather than the producers of the salt. But these are matters that deserve further investigation. The detailed character of this industry and its role in Iron Age society remain on the agenda for future research.

Acknowledgements

The 2001 project is led by the Department of the Iron Age, Musee des Antiquites Nationales Saint-Germainen-Laye, France, for the Departement de la Moselle. Phase I of the project, organised over the five year period 2001-2005, has consisted mainly of geophysical investigations. Conducted in cooperation with the Bureau de Recherche Geologique et Miniere (BRGM, Orleans, France), the Bundesanstalt fur Geowissenschaften und Rohstoffe (BGR, Hanover, Germany), performed the first systematic multi-spectral survey of the entire valley by helicopter survey, while target geomagnetic prospection was carried out by the private geophysical survey firm Posselt & Zickgraf Prospektionen (PZP, Marburg, Germany).

Received: 8 February 2005; Accepted: 18 May 2005; Revised: 13 June 2005

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Laurent Olivier (1) & Joseph Kovacik (2)

(1) Conservateur du Departement des Ages du Fer, Musee des Antiquites Nationales, 78105 Saint-Germain-en-Laye, cedex, France

(2) Archaeological Development Services Ltd, Westilink Enterprise Centre, 30-50 Distillery Street, Belfast BT12 5BJ, UK