Chapter 3 – The Data .............................................................................................................................. 2
Introduction ........................................................................................................................................ 2
Data Collection and Quality ................................................................................................................ 2
Chronological Discussion .................................................................................................................... 7
Geographic Discussion ........................................................................................................................ 9
Site Types .......................................................................................................................................... 13
Iron Working Evidence ...................................................................................................................... 14
Other Evidence.................................................................................................................................. 15
Conclusion ......................................................................................................................................... 15
Bibliography ...................................................................................................................................... 16
Maps are at the end of the document
Data Analysis Chapter
Introduction
This chapter will present the results of the data-gathering phase of the research; discussing in detail
what was collected, for what reason, the quality of the data and then presenting the results under
the various headings used in the project database. The data entered for every field in the final
database will be discussed, though not necessarily in detail. Discussion will largely be about ‘what
was found’ rather than ‘what it means’: this will be addressed (at least to some extent!) in the
subsequent chapters.
Data Collection and Quality
The collection of data was fundamental to the PhD project in that it would influence and effect all of
the conlusions drawn, it had the potential to introduce significant biases and it was one of the most
time-consuming elements of the project.
Fig. 3.1 The Database Structure
Description of the Database
The database was built in Microsoft Access and was based around a central table called the Master
Database. Three important sub-tables were created to record radiocarbon/dendrochronological
dates, individual smelting furnaces/hearths and individual charcoal pits. The first two turned out to
be very significant but the lack of evidence for contemporary charcoal production on most sites (see
discussion below) meant the charcoal table was less important.
Tables were also created to record both the details of individual excavations (various licence
numbers, companies, directors etc) and to link to scanned images relating to each site. In the end
input of data into the excavation details table was abandoned as sufficient information was
incorporated in the Master Database table. Time constraints meant that the image table was only
used in a limited way. A number of look-up tables were also created to ensure accurate data entry
for particular database fields (e.g. Site Category, Site Type, Institution, County, Find Circumstances).
A series of individual fields were also created to record various aspects of site layout, features and
ironworking remains. These are discussed below.
Data Selection
A thorough trawl of the published and unpublished literature for sites with ironworking evidence,
most commonly in the form of slag, that might date to the projects chronological focus resulted in
407 sites being identified and entered into the database (Appendix ?). While all of these sites
appeared, at least initially, to relate to bloomery, charcoal-based ironworking, recent evidence for
the survival of such techniques until the nineteenth century (see chapter 2) means that only those
with some evidence dating them to the Early Medieval Period or earlier were included in the study.
Two sites: Murlough Bay and Lough Enagh, listed in Scott’s (1990) database proved to be duplicates
of other sites he recorded and so they were also excluded. One final site, Lough Gowna where slag
was reported was also excluded as the slag proved to be a naturally occurring iron ore deposit. The
balance of the excluded sites was made up of 105 sites of unknown date and 31 sites dated to the
medieval period or later. This left some 268 sites which have been included in the final study and
are discussed in detail in this chapter.
Data Sources
Data was collected from a variety of sources, both published and unpublished. Two sources were
extremely useful for identifying potentially relevant sites: Scott’s (1990) appendix of the (then)
known sites with evidence for ironworking in Ireland and the published excavations bulletins up to
2005. O’Sullivan and Harney (2008) and Becker et al (2008) were also valuable sources of
information for the early medieval and Iron Age periods respectively.
Once potentially relevant sites were found a thorough search of online databases and bibliography
was undertaken in order to identify available published or unpublished literature. Where this was
unsuccessful and the site warranted it, further attempts to acquire any unpublished material were
made by emailing relevant directors, companies and specialists.
Out of the 407 potential sites identified, by far the largest proportion were excavated by commercial
companies or directors with government bodies, universities, museums and other bodies accounting
for the bulk of the remainder. The influence of the commercial sector is slightly less pronounced in
the final corpus of sites included in the study (discussed below) but not drastically so. The drop is
largely due to the significant number of sites for which only summary information, not including any
dated material, is available. Still, it is clear that the last twenty years of intensive excavation has
contributed significantly to the quantity of data available relating to early ironworking in Ireland.
Fig 3.2 Sectors responsible for the excavation of potential sites (left) and sites included in the study (right).
Data Quality
Chronology
The quality of data from the various sites in the database is highly variable and some means of
classification was seen as crucial. For this reason fields were created within the database grading the
quality of the chronological information available as well as the level of information (termed
‘publication status’) available. A final field recorded sites that were of particular interest due to
abundant evidence, unusual preservation, unusual features or artefacts, or any other uncommon
attributes.
Fig. 3.3 Chronological grading of sites included in the study (Grade 6 sites were not included in the study)
Chronological information was graded according to seven numerical labels detailed in Table 1. Sites
within the first two categories (1 and 2) have very well dated ironworking evidence and constitute
42% (111) of the sites included in the study. This is a significant group of reliably dated sites and
their specific chronologies are discussed in detail later in the chapter. More than half of the sites
included in the study are graded from 3 to 5, these dates must be treated with some suspicion as
they are not directly dated and rely on assumptions based only on spatial association and/or dating
through site morphology; none of which are very reliable.
Dendrochronological dates are by far the most reliable dates available for sites in the study but they
were available for only a very small minority of sites including Deer Park Farms, Moynagh Lough,
Coolcran and Bofeenaun. Radiocarbon dates can also be fairly reliable but this is not invariably the
case. Unfortunately the tendency of early metalworkers to use oak charcoal when smelting and
smithing means that often long-lived oak is the only datable material available to excavators. This
means that the ‘old wood effect’ is likely to be very significant and radiocarbon dates for particular
sites cannot always be taken at face value (cf. Warner 1987).
Dating using artefacts can be extremely variable in terms of accuracy with some artefacts being
quite closely datable (e.g. coins) and some only very broadly datable (e.g. jet/lignite bracelets).
Pottery has also been used to date a number of sites and can sometimes be used to date within a
fairly close range (e.g. E-ware and B-ware; REFERENCE) although in the case of souterrain ware the
date range is longer and not as certain (Armit 2008).
A large number of sites are dated to a particular period due to their association with a particular site
type such as a ringfort, crannog, ring-ditch or monastic site. While dates such as this can in some
cases be fairly confidently trusted when viewed in the context of other artefacts and features they
are still based on assumptions and parallels that may not be entirely reliable. Due to the complexity
and variety of sources, strengths and problems with dates, conclusions drawn at a national level
have to be crude and more detailed analysis and critique must be undertaken in the context of later
discussions of specific sites and groups of sites.
1
Direct date(s) from the ironworking evidence (e.g. fill of a furnace or working
surface) using scientific dating (Radiocarbon, dendrochronology etc)
2
Reasonably close dating of the ironworking evidence through stratigraphic
associations with well dated layers or artefacts
3
Ironworking dated by association with a site which has absolute dates but no
direct stratigraphical relationship (e.g. a furnace located adjacent to a dated
ringfort)
4
Ironworking broadly dated by association with a particular site type (e.g. a
ringfort, moated site, ring ditch etc)
5
Evidence collected from the surface. May be tentatively dated by association with
other artefacts or a particular site type.
6
No dating evidence available.
0
Site dated by another authority but not clear what this is based on or original data
(e.g. radiocarbon dates) unavailable.
Table 3.1: Criteria for grading of chronological information.
Publication
Sites included in the study represent a wide spectrum in terms of publication status (Fig. 3.4). While
a fairly large proportion (44%) have been fully published this is no guarantee that specialist analysis
has been carried out or even that adequate description in terms of weight, quantity etc has been
given. In fact a significant chunk (70 sites or 60%) of the published sites (118 in total) were included
in Scott’s database and display the shortcomings of most early excavations when dealing with the
ironworking evidence (See Chapter 1).
Fig. 3.4 Publication status of sites included in the study.
Some sites have been classified as part-published, these include sites such as Clonmacnoise and
Moynagh lough where significant data has already been made available but for which further
significant publications are expected, as well as sites that have seen interim or summary reports
appear in print. The unpublished reports category includes sites where it was possible to obtain
either interim or full excavation reports that have not yet been published. These generally have a
good standard, giving full stratigraphic information, dating evidence and, often some level of
specialist analysis. Unpublished sites include those mentioned briefly in print (e.g. unpublished sites
in Scott’s database), sites summarised in the excavations bulletin and sites where information is
available in online form from the NRA database or Archaeology.ie.
Fig. 3.5 Sites with some level of specialist analysis
Sites for which it was possible to obtain specialist reports (totalling only 72) do not overlap in any
simple way with those that are published. In fact, for 28% of sites only a specialist report was
available (fig. 3.5). This is due to the generosity of some specialists in making their material available
and the difficulty in making contact with excavators and acquiring excavation reports for the same
sites. In reality the gold standard in terms of publication status can best be approximated by sites
fully published with specialist analysis (35 sites) or unpublished with a final report including specialist
analysis (11 sites).
Conclusions
The collection, collation and classification of data in the project database was extremely timeconsuming and the quality and quantity of material available has been variable and very difficult to
predict. Information was collected from a huge variety of sources, some which were easily accessed
and others less so. In the end a substantial and significant corpus of information has been gathered
but the varying standards of quality and type require that interrogation of the material is done in an
extremely critical manner. Indeed, sites which reach the gold standard in terms of publication status
as well as either 1 or 2 on the chronological grading system amount to only 33 out of the total 268
sites or only 12% of the sites considered in the study.
In fact out of the 268 sites included in the study there are only 24 sites fully published with specialist
analysis and chronological data rated at 1 or 2. There are also 9 unpublished sites with final
excavation reports and specialist analysis carried out. Together these sites represent only 12% of the
sites in the study.
Chronological Discussion
The project focuses on excavated ironworking sites dating prior to the medieval period in Ireland.
The focus is on sites and technologies that existed prior to the arrival of Norse and Norman
craftsmen who may or may not have brought new smithing and smelting methodologies to the
country (a question beyond the scope of this study but being tackled through another PhD project
being undertaken by Paul Rondelez in University College Cork).
This is essentially the same period covered by Scott who split it into three periods based on a
theoretical model of how iron technology is adopted into a society. Early Iron Age A (ca 7th-3rd
centuries BC) related to a period of transition to iron as the primary industrial metal. Early Iron Age B
(ca 3rd century BC – 5th century AD), related to a period when iron was becoming established as the
primary industrial metal and influences from Roman, post-Roman and Germanicised British spheres
were being seen. And finally Late Iron Age A (ca 6th-10th centuries AD) when iron afrtefacts first
became ubiquitous in everyday life. Scott classified the 10th- 12th centuries as Late Iron Age B, a
period when Scandinavian immigrants supposedly finally brought Irish ironworkers into contact with
the mainstream of European iron technology. While some sites in my study may have dates that
span somewhat into this period, it is not within the focus of the study.
Scott’s divisions are based on a theoretical framework that seems to work on a simple level but its
application at a national scale and based on the small amount of information available to him is
perhaps over-ambitious. They also treat the evidence for ironworking in isolation from wider societal
changes, an artificial division that should preferably be avoided. For this reason I decided to use
traditional chronological labels which, while bringing their own baggage, make it easier to consider
the ironworking evidence in relationship to other strands of evidence based on similar chronological
concepts.
Table 3.2 Chronological Periods used in the study
Bronze Age
Prior to c.600 B.C.
Iron Age
c. 600 B.C. – c. A.D. 400
Early Medieval
c. A.D. 400 – c. A.D. 1000
Medieval
c. A.D. 1000 - c. A.D. 1500
Late
c. A.D. 1000 - Present
Chronological Periods
Assigning broad chronologies to sites is not a straightforward process as sites are sometimes multiperiod and dates can have very wide ranges. Nonetheless an attempt was made in order to give a
broad view of the chronology of the ironworking evidence (Fig. 3.6). Sites which dated to more than
one period are designated either or e.g. Iron Age/early medieval in the case of Tonybaun.
Fig. 3.6 Broad chronology of sites included in the study
A brief look at the data immediately shows that the majority of sites date to the Early Medieval
Period with a much smaller number earlier in date. This reflects the wider archaeological record
which has consistently revealed far more evidence for human activity in the Early Medieval Period
when compared with the preceding millennium. The 18 sites classified as Iron Age/Early Medieval
are of particular interest as they date close to a transition period between the transformation of
society with the coming of Christianity and the explosion of human activity in the landscape visible in
the early medieval period (e.g. EMAP).
Another potential explanation of this tendency for sites to be dated to the early medieval period
could be the many sites dated through site morphology to the early medieval period, particularly
ringforts (a site type that has recently been heavily challenged (Fitzpatrick, Kinsella). However,
looking only at the sites with high quality dating information (Grade 1 and 2) gives a surprisingly
similar picture (fig. 3.7). There are 62 sites dating to the early medieval period and only 24 firmly
dated to the Iron Age, about a third as much.
Fig 3.7 Broad chronology of sites included in the study graded 1 or 2.
Nonetheless this is a significant number of well dated sites which allow considered analysis of the
chronological changes in the role of iron in society over the iron age and early medieval periods.
These will be teased out further and with reference to individual sites in Chapters 4-7.
Geographic Discussion
The location of ironworking in the landscape is very significant in terms of how people perceived it
and the people who carried it out. Ethnographic studies have shown that where people carry out the
various processes associated with ironworking (e.g. within settlements or in designated, isolated
areas) can be a product of fundamental societal attitudes towards its products and practitioners.
On a local and regional scale differences in where people carried out particular activities may
provide indications of differing technological, or social practices that may represent different social
groups. When the geography of ironworking is looked at nationally similar differences may be
discerned, and when compared with constraining influences such as the availability of raw material
inferences can be drawn about the choices people made in the past when making and using iron.
This section will attempt to look at the location of ironworking sites in Ireland on a national scale in
order to provide a background to smaller scale case studies in Chapters 4 and 5.
Site Distribution
Scott’s original study of Irish ironworking neglected to consider where it was occurring but it he did
identify sites from most counties in Ireland. Nonetheless there was a definite bias towards sites in
Northern Ireland (Plate 1) where a significant number of excavations with ironworking evidence had
been carried out and published in the Ulster Journal of Archaeology. Other sites are spread around
the country and mainly reflect the geographic and research priorities of academic archaeology.
Sites identified in this study reflect a similar distribution, with some in-filling of previously blank
areas, for example in Munster. However, some counties such as Meath, Cork and Dublin have shown
a huge rise in the number of known sites. This is largely due to the effect of the massive roadbuilding and other infrastructural projects that have taken place in the last two decades. So much
evidence has been uncovered through these that sites in the counties surrounding Dublin can be
seen to radiate along major road routes such as the M3, M4 and M7 (Plate 1). Counties such as
Leitrim, Carlow, Longford, Cavan, Donegal, Monaghan, Wicklow and Wexford, which have not seen
major infrastructural projects show correspondingly low numbers of sites.
Fig. 3.8 Sites per county
It is difficult to interpret the distribution of these sites apart from noting that they represent,
unsurprisingly, widespread working of iron in Ireland. There are some areas of absence such as much
of Galway and in some areas where infrastructure has been built corresponding ironworking
evidence is not in evidence (e.g. stretches of the M11 on the east coast. However it is not clear
whether these are real gaps or if they are related to lack of excavation and/or publication.
Chronological changes
It is not necessarily the case that there should be a difference between the distribution of iron
workers and their residues in the Iron Age when compared with the early medieval period. This is
particularly true of places where iron ores were available and continuity of smelting activity would
not be unusual unless the ore source was extinguished (unlikely in the case of bog ore), a better
source was found, or societal pressures (e.g. war, economic collapse, migration) led to the
abandonment of iron smelting in a particular area.
It is far more likely that differences in areas where secondary smithing takes place would be
apparent. This is an activity which can take place anywhere from the local farm to an industrial
centre and its actual location would have been dictated by tradition. At the same time these types of
changes could be on a local enough scale (e.g. movement of smithing activities from the vicinity of
an Iron Age ritual site to a nearby monastery) that it would not be visible on a large-scale map.
When sites in the study dated firmly in the Iron age are plotted against those definitely dating to the
early medieval period, some differences can certainly be seen (Plate 2). Iron Age sites are most
common in the midlands (a potentially rich source of bog ore) but are also spread around the
country, often occurring close to the mouths of rivers such as the Shannon, the Suir and the Lee.
Surprisingly, considering the evidence for high status non-ferrous metalworking in the region during
the Iron Age and the large number of sites excavated, early sites are rare in the northeast.
Early medieval sites are far more common and spread throughout the country (Plate 2). Again, there
are a fairly large number of coastal sites which raise questions about the potential for trade, but in
fact ironworking sites are liberally spread around the country reflecting a developed iron industry
with technical knowledge existing throughout the country. The distribution also reflects a more
general difference in the number of known sites between the two periods which holds true for all
types of archaeological evidence, not just that related to iron.
Need map of smelting/smithing sites in IA/EMED
Smithing and Smelting
The identification and differentiation of the smelting and smithing processes on sites is one of the
primary goals when analysing ironworking residues but it can be difficult to carry out in practice. This
is particularly true in Ireland where understandings of the morphology of smelting and smithing slags
are in their infancy and old assumptions about Irish iron technology have been strongly questioned
(see Chapter 3). However, it was possible to identify smelting and/or smithing activities in a
substantial number of sites that had either specialist analysis carried out or other clear evidence
such as furnace features or anvils.
When these sites are mapped (Plate 3) it is clear that, as could be expected, smithing residues have
been found throughout the country and show no particular concentration. However smelting sites
show two interesting trends. The first is a large cluster in the midlands of Ireland and the second is a
series of smaller clusters in north mayo, the east coast and the south coast of Ireland.
It is probably premature to see some of these clusters as particularly significant as they are often the
product of availability of funds for specialist analysis on a particular roads scheme. However, the
large cluster of smelting sites in the midlands west of Dublin does seem very significant. Many of the
sites were identified in the course of road schemes but their frequency and density has not been
reflected on other schemes. Also, when these sites are seen in relation to a map of bogs in Ireland
(Plate 4) it is clear that they occur within a large area of raised bog.
This area is known to have sources of bog ore utilised in the past (e.g. at Clonfad: Young 2005;
Stevens 2006) and samples have been collected as part of this study from Derryarkan Bog, Co.
Offaly. It would seem that this area may have been a major source of iron in the Iron Age and early
medieval periods. This idea will be returned to later (see Chapter ?).
The other potential sources of iron ore are mineral and when plotted against known smelting sites
don’t show any obvious correlation. This may be due to data problems. The data for mineral ore
sources in Ireland on comes from the Geological Survey of Ireland and maps only sources that are
big enough to register as important for modern geological studies. Smaller, localised deposits and
exhausted deposits will not be mapped and it is possible that some of the smelting sites drew on
such sources. It is also possible that some ore could have been imported to Ireland for smelting,
although it would seem more effective to import iron billets or finished implements rather than
bulky ores, even in areas where native ores were scarce.
Need map of road schemes
Need map of iron age smelting/smithing and emed same
Intrasite spatial discussion
A number of fields were included in the database to attempt to get a general sense of the location of
ironworking activities within sites. This is not an easy element of the data to capture in a few fields
and will be teased out far better in later chapters looking at particular case studies.
Fig. 3.9 Cardinal location of ironworking areas within enclosures
On sites where it was applicable, such as ringforts, monastic enclosures and crannogs that had
obvious central points, ironworking areas were recorded in terms of which cardinal area of a site
they occurred on. This applied only to areas where either smelting or smithing had taken place and
not to dump sites. The results show absoloutely no pattern, suggesting that the location of
ironworking on such sites was random and that ironworkers could work in essentially any part of an
enclosure, regardless of its cardinal direction.
Another field recorded sites where clear ‘discrete areas’ could be discerned where ironworking was
being carried out. This included some 36 sites all of which included activity of some other type
including burial, settlement, cereal drying etc. Another 14 sites were classified as isolated
ironworking sites. These were sites with no evidence for any activity apart from ironworking. In fact
this is a fairly common type of site and there are another 18 undated examples that were not
included in the study due to a lack of dating evidence.
The location of ironworking within sites does not appear to follow any particular pattern and it is
actually not uncommon for it to exist in isolation from any other archaeological evidence. However,
when it does occur in settlement or other contexts the actual location of ironworking or ‘discrete
area’ is generally not identified. The majority of sites leave only evidence in the form of stray slag,
slag dumps or isolated features with metallurgical material. The evidence suggests that people were
not working their iron in a set way and that the best way of considering intra-site spatial distribution
is through individual site studies.
Site Types
Categorisation of sites into ‘site types’ is difficult and necessarily removes nuance and enhances
conformity, but it can be useful in terms of getting a broad picture of the data being analysed. For
this reason sites were identified according to a set list of ‘site categories’ (Table 3.2)
Table 3.2 Site Categories
Site Type
Ringfort
Ironworking Site
Indeterminate
Ecclesiastical
Monastic
Enclosure
Crannog
Burial
Settlement Complex
Ring Ditch
Prehistoric
settlement/cemetery
Charcoal Production
Souterrain
Hillfort
Cereal drying Kiln
Hut Site
Quantity
70
37
37
20
17
13
12
10
10
7
5
7
4
4
3
2
2
Raised Rath
Cave
Earthwork
Promontory Fort
Royal Site
Stone fort
Need map of Site Types
Iron Working Evidence
Tuyeres
Slag
Weight, types
Smithing Floors
Hearths
Furnaces
Average Size
Shape
Date
Roasting
Furnace Lining
Blooms
Ore
Anvils
Hammerscale
Tools
Associated Features
Postholes
Middens
Charcoal Production
Raw Material
2
1
1
1
1
1
Morphology
Date
Other Evidence
Bullauns
Whetstones
Non-ferrous Metalworking
Cereal Drying Kilns
Burials
Other Industrial Activities
Glass
Jet
Conclusion
Bibliography
Armit, I. (2008) Irish–Scottish connections in the first millennium AD: an evaluation of the links
between souterrain ware and Hebridean ceramics. Proceedings of the Royal Irish Academy,
108, 1-18.
Becker, K., Ó'Néill, J. & O'Flynn, L. (2008) Iron Age Ireland: Finding an Invisible People. Archaeology
Grant Scheme Project 16365, Report for the Heritage Council.
O'Sullivan, A. & Harney, L. (2008) Early Medieval Ireland: Archaeological Excavations 1930-2004,
Early Medieval Archaeology Project (EMAP) Report 2.1, Unpublished Report for the Heritage
Council.
Scott, B. G. (1990) Early Irish Ironworking, Belfast, Ulster Museum.
Stevens, P. (2006) A monastic enclosure site at Clonfad, Co. Westmeath. Archaeology Ireland, 20, 811.
Warner, R. B. (1987) A proposed adjustment for the 'Old Wood Effect'. In Mook, W. & Waterbolk, H.
T. (Eds.) Proceedings of the 2nd Symposium of 14C and Archaeology, Groningen 1987.
Strasbourg, Council of Europe.
Young, T. (2005) Evaluation of archaeometallurgical residues from Clonfad 3, Co. Westmeath.
GeoArch.
Plate 1 Location of all sites in the study showing sites identified by Scott and those identified in this
study.
Plate 2 Distribution of sites with definite Iron Age or Early Medieval dates.
Plate 3 Sites with definite evidence for smelting and/or smithing.
Plate 4 Distribution of blanket (in black) and raised (in grey) bogs and sites with definite evidence for
smelting.
Plate 5. Distribution of iron ore deposits in Ireland and sites with definite smelting evidence.