Rethinking the quest for provenance.

Rethinking the quest for provenance. One of the larger - and more expensive - present programmes of studyin archaeological science Archaeological science (also known as Archaeometry) is the application of scientific techniques and methodologies to archaeology.Archaeological science can be divided into the following areas: explores the provenance prov��e��nance?n.1. Place of origin; derivation.2. Proof of authenticity or of past ownership. Used of art works and antiques. of prehistoric bronzesfrom the Mediterranean. What are the bases of research? What will thefindings tell us about the real place of metal as it moved in theancient world?The provenance postulate postulate:see axiom. The availability of spectrographic spec��tro��graph?n.1. A spectroscope equipped to photograph or otherwise record spectra.2. A spectrogram.spec methods in the 1930s made itpossible to analyse large numbers of ancient metal artefacts with a viewdetermining their provenance. Some of these studies (e.g. Pittioni 1957)followed from a 19th-century tradition, pioneered by the Austrianscholar Wocel (see Caley 1951; 1967), in which it was proposed that theimpurities in ancient copper artefacts would directly reflect those inthe ores from which they were smelted. Some scientifically informedcommentators (Thompson 1958) expressed concern as to whether this naiveinsistence was justified, but the work continued in the absence of anydetailed understanding either of the geology of metal ores or of thechemistry of their smelting smelting,in metallurgy, any process of melting or fusion, especially to extract a metal from its ore. Smelting processes vary in detail depending on the nature of the ore and the metal involved, but they are typified in the use of the blast furnace. . Although most researchers have come torecognize the complexity and limitations of compositional data In statistics, compositional data are quantitative descriptions of the parts of some whole, conveying exclusively relative information.This definition, given by John Aitchison (1986) has several consequences: A compositional data point, or composition (see forexample Pernicka 1995), Pittioni-style provenance studies continued fordecades. Despite Thompson's warning, tens of thousands ofprehistoric metal artefacts were subsequently analysed. The Studien zuden Anfangen der Metallurgie (SAM) analytical programme (Junghans et al.1960; 1968; 1974) and the huge analytical programme in the former SovietUnion (Chernykh 1994) stand as the two largest monuments to thisendeavour. Interpretation of the data in these compilations hasgenerally used statistical procedures to extract groups of artefactshaving similar composition. On the broadest level, such groupings areundoubtedly significant. In much of Eurasia, the use of unalloyed un��al��loyed?adj.1. Not in mixture with other metals; pure.2. Complete; unqualified: unalloyed blessings; unalloyed relief. copperpre-dates the use of arsenic-rich material, and this is later succeededby tin-bronze. On a more detailed level attempts to link compositionallysimilar artefacts to common geographical sources have almost alwaysproved inconclusive. Artefacts grouped on the basis of composition haveoften come from unrelated contexts, sometimes widely scattered acrossvast areas, as Butler & Van der Waals (1964) noticed in commentingon the SAM programme.When the assumptions which underpin these approaches are examined, itis easy to see the pitfalls. For trace element provenancing to succeedit is necessary to assume that the artefacts under consideration werefabricated fab��ri��cate?tr.v. fab��ri��cat��ed, fab��ri��cat��ing, fab��ri��cates1. To make; create.2. To construct by combining or assembling diverse, typically standardized parts: using similar manufacturing processes, derived from astrictly limited number of sources and smelted in such a way as toproduce a metallic product with a limited range of impurities.Furthermore, one is obliged to make further fundamental assumptionsabout alloying and recycling. Whereas some copper deposits may containdistinctive traces of particular trace or minor elements, very few havebeen studied mineralogically to the point where quantitative estimatesof different mineral species' contributions to ore 'as-minedin prehistory' can be made. Similarly, there is little detailedunderstanding of the behaviour of impurities in primitive smeltingprocesses. Simple thermodynamic ther��mo��dy��nam��icadj.1. Characteristic of or resulting from the conversion of heat into other forms of energy.2. Of or relating to thermodynamics. models are problematic and manyexperimental studies have been little more than imaginativereconstructions of hypothetical processes, sometimes using inappropriatematerials and poor control and monitoring.Under these circumstances modern researchers are rightly circumspect cir��cum��spect?adj.Heedful of circumstances and potential consequences; prudent.[Middle English, from Latin circumspectus, past participle of circumspicere, to take heed : in their use of impurity im��pu��ri��ty?n. pl. im��pu��ri��ties1. The quality or condition of being impure, especially:a. Contamination or pollution.b. Lack of consistency or homogeneity; adulteration.c. data for provenance studies, although usefulstudies have been undertaken for small regions; attempting for exampleto outline compositional variation within artefacts already groupedarchaeologically by virtue of typology typology/ty��pol��o��gy/ (ti-pol��ah-je) the study of types; the science of classifying, as bacteria according to type. typologythe study of types; the science of classifying, as bacteria according to type. or context (e.g. Begemann et al.1995). It is now clear that different deposits may share closely similargeochemical characteristics so that particular copper deposits simplywill not yield metal of unique minor or trace element composition. Onthe other hand, some deposits may be distinctive from some others withrespect to certain elements, and Pernicka (1995) argues cogently co��gent?adj.Appealing to the intellect or powers of reasoning; convincing: a cogent argument.See Synonyms at valid.[Latin c thattrace element analysis offers the potential to aide the discriminationof ore sources in some cases.These observations about the studies of a generation ago and thelimitations of trace element analysis are paralleled in recent work onlead isotopes - work regarded as the promising successor to elementalanalysis Elemental analysis is a process where a sample of some material (e.g., soil, waste or drinking water, bodily fluids, minerals, chemical compounds) is analyzed for its elemental and sometimes isotopic composition. for provenance study. Some practitioners of lead isotopeanalysis Isotope analysis is the identification of isotopic signature, the distribution of certain stable isotopes and chemical elements within chemical compounds. This can be applied to a food web to make it possible to draw direct inferences regarding diet, trophic level, and subsistence. were amongst the most vociferous critics of trace element metalprovenancing (e.g. Gale & Stos-Gale 1982); yet, in developing theirmethods, these workers themselves retain some of the same assumptionsregarding the composition of ore bodies and concerning the nature ofmetal production and use in prehistoric societies. Although not obviousin the early years of the large-scale lead isotope isotope(ī`sətōp), in chemistry and physics, one of two or more atoms having the same atomic number but differing in atomic weight and mass number. The concept of isotope was introduced by F. programmes, when thenumbers of ore bodies and artefacts analysed were relatively small, asthe data have accumulated so too have many familiar problems. Thesedifficulties could undermine the whole lead isotope provenancingtechnique if they lead to a loss of faith of the sort that overtook o��ver��took?v.Past tense of overtake. theSAM programme (Coles 1982). In our opinion, this need not be the case.Lead isotope studies can be helpful and relevant in archaeology. Webelieve however, that more realistic archaeological interpretations ofthe analytical data are required; a more detailed examination ofarchaeological lead isotope methodology and the deconstruction deconstruction,in linguistics, philosophy, and literary theory, the exposure and undermining of the metaphysical assumptions involved in systematic attempts to ground knowledge, especially in academic disciplines such as structuralism and semiotics. ofaspects of the current framework are essential to this.Deconstructing lead isotope provenancingA vigorous debate on the interpretation of lead isotope data hasrecently taken place in Archaeometry (Sayre et al. 1992a; 1992b; 1993;Gale & Stos-Gale 1992; 1993; Leese 1992; Pernicka 1992; 1993; Reedy reed��y?adj. reed��i��er, reed��i��est1. Full of reeds.2. Made of reeds.3. Resembling a reed, especially in being thin or fragile: & Reedy 1992; Budd et al. 1993a; 1993b) and in the Journal ofMediterranean Archaeology where it focuses on the Aegean Bronze Age Bronze Age,period in the development of technology when metals were first used regularly in the manufacture of tools and weapons. Pure copper and bronze, an alloy of copper and tin, were used indiscriminately at first; this early period is sometimes called the (Budd et al. 1995a; 1995b; Gale & Stos-Gale 1995; Pernicka 1995;Sayre et al. 1995; Hall 1995; Muhly 1995). However, this concern overlead isotope research is not new. Some archaeologists have, for a numberof years, been drawing attention to a growing gulf between theconclusions drawn from some lead isotope programmes, and those of theirown research work (e.g. Cherry & Knapp 1991; Knapp in press; Knappet al. 1988; Muhly 1991; 1995). This controversy has disconcerted dis��con��cert?tr.v. dis��con��cert��ed, dis��con��cert��ing, dis��con��certs1. To upset the self-possession of; ruffle. See Synonyms at embarrass.2. thosewho would like to rely on the analytical results, frustration evident ina recent editorial in this journal (Chippindale 1994). It is becomingclear that the interpretation of lead isotope data has not taken placewithin a framework which reflects the true complexity either of oredeposits, or - perhaps more importantly - of metal supply andcirculation in the ancient world. We contend that this crisis ofconfidence stems, not from lead isotope measurements themselves, butfrom their interpretation.As modern mass spectrometers are capable of measuring lead isotoperatios to a high degree of precision, one should be able to haveconsiderable confidence in the accuracy of published data. Thepreparation and analysis of lead-bearing metals or minerals is a routineand simple task usually undertaken by experienced technicians. Lead-poormaterials (Cypriot copper ores, for example) can be more problematic,but again tried and tested methods have been developed to processsamples on a routine basis. Unfortunately, recent experience withre-measuring 'outliers' (Gale & Stos-Gale 1992) and therejection of old measurements in new data compilations (Stos-Gale et al.1995) have shown that some measurements appear not to have been of thehighest precision. This makes it impossible to define accurately thefull extent of the Cypriot and other important ore source fields, asituation that could be resolved by a systematic re-measurementprogramme.The relative simplicity of lead isotope analysis extends to theinterpretation of lead isotope data. As there are only four naturallyoccurring lead isotopes which must add up to 100%, there are only threeindependent variables. Every sample can be completely characterized bythree numbers and all that is required to express every attribute of thedata is a three-dimensional plot. Multivariate analyses (Sayre et al.1992) or discriminant function discriminant functionn. StatisticsA function of a set of variables used to classify an object or event. analyses (Gale 1991) can be applied, butthe usefulness of such approaches is strictly limited. With only threevariables and three axes on which to plot them, sophisticatedmultivariate approaches are, at best, unnecessary. Discriminant functionanalyses can be used to select rapidly the best projection ofthree-dimensional data in order to see the greatest separation betweengroups of samples from different ore deposits. However, it can only beused to calculate the probability of an unknown sample belonging to onesuch group under the right circumstances: where all possible groups arerepresented, and where all are fully characterized by statisticallysignificant numbers of samples. This is a rare happening inarchaeometallurgy.All that is actually required to interpret lead isotope data is athree-dimensional plot of the ore data and artefacts underconsideration, together with appropriate computer software to rotate andview it. This can be done using the humblest personal computer. There isno reason why archaeologists or archaeological scientists should bemarginalized in the interpretation of lead isotope data as even the mosttraditionally based archaeologist routinely deals with much more complexdata-sets. What is needed, in the words of one of the referees of thispaper, is 'publication of the mineral data - for samples of statedarchaeological and geological characteristics - in a simple,straightforward and workable way'.Proponents of the lead isotope method of provenancing initially hopedthat specific metalliferous regions, be they individual islands such asCyprus or Kythnos or mainland deposits such as Lavrion, would have theircharacteristic isotope 'signatures' - each significantlydifferent from one another. In this sense, the programmes can be seen asthe isotopic i��so��tope?n.One of two or more atoms having the same atomic number but different mass numbers.[iso- + Greek topos, analogue of those of SAM or Pittioni. There would be somenatural variation in lead isotope composition within each region, butinitial measurements seemed to justify optimism that this would berelatively small. This being so, each region could be characterized by arelatively tight grouping of similar ratios which could be plotted as a'field' on a three-dimensional diagram or on pairs oftwo-dimensional plots. The variation in the four naturally occurringlead isotopes in an ore body is related to the genesis and age of thedeposit. For archaeological purposes this detailed geologicalinformation is largely superfluous su��per��flu��ous?adj.Being beyond what is required or sufficient.[Middle English, from Old French superflueux, from Latin superfluus, from superfluere, to overflow : . Provided that each ore field ischaracterized by sufficient numbers of analyses and the variationbetween sources in the region under consideration remains large, then itshould be possible to comment on the provenance of objects of unknownorigin.It was never going to be practical to define every ore deposit in theancient world, and workers were initially forced to define source fieldson less than ideal numbers of analyses. Provided that the analysts werejustified in their assumptions, regarding the limited spread of datafrom an individual ore body and the variation between fields within theregion under scrutiny, then provenance analysis could proceed with costskept within reasonable bounds. Unfortunately, it is now clear that theirinitial assumptions about ore bodies were not well founded. As the workprogressed, it became evident that the variation within many of the oresources of interest was much greater than had been hoped and that manyfields defined in a region, such as the Mediterranean, overlapped eachother.The often-heated debate in Archaeometry and JMA jma Jour Mois Ann��e (French: day month year)JMA Japan Management AssociationJMA Japan Medical AssociationJMA Japanese Meteorological AgencyJMA Jamaica Manufacturers' AssociationJMA Joint Marketing Agreement essentially centreson this point, in a detailed discussion likely to lie beyond theinterest of any but the most scientifically minded archaeologists. Atthe heart of the argument is this: do ore source fields, defined usingstatistical procedures on selected data rather than the required numberof analytical measurements, have any validity? We maintain that they donot. In order to maintain apparent separation between source fields, theOxford group have suggested that all of the ore sources of theMediterranean have lead isotope fields which display little variationand therefore form very tight and discrete fields on plots of the data.They imply, incorrectly, that this is because all of the ore deposits inquestion conform to Verb 1. conform to - satisfy a condition or restriction; "Does this paper meet the requirements for the degree?"fit, meetcoordinate - be co-ordinated; "These activities coordinate well" a model based on a single emplacement event ingeological time. In reality only a small minority of ore deposits meetthe stringent requirements for this type of geological conformability con��form��a��ble?adj.1. Corresponding; similar: plans that are conformable to your wishes.2. Quick to comply; submissive.3. .One of the most important deposits, Cyprus, is one such rare example,but other Mediterranean deposits certainly are not.The Brookhaven/Smithsonian group have taken this questionableprocedure a stage further. Ignoring the fundamental geology thatunderpins lead isotope analysis, they have assumed that data from eachore field would be normally distributed with respect to each of thethree measured ratios (Sayre et al. 1992a). This assumption oftri-variate normality normality,in chemistry: see concentration. is not likely to be correct (Cherry & Knapp1991; Budd et al. 1993a; 1993b; Scaife et al. in press). The sourcefields that seem more precisely defined are achieved by rejecting'outlying' samples collected from an ore body but somehow notthought to be representative of its lead isotope field (see Budd et al.1993a). In attempts to define source fields still more tightly, someworkers have proposed breaking up some, already ill-defined, sourcefields into subsets (Sayre et al. 1992; Gale & Stos-Gale 1992). Thiscan only lead to confusion. In extreme cases proposed sub-groups havebeen defined by as few as two measurements and represent single mineswhereas neighbouring mines, only a few kilometres distant, aresupposedly represented by entirely different fields!A full consideration of the geology of ore formation suggests thatcompact and discrete lead isotope fields for individual ore deposits arelikely to be the exception rather than the rule. In contrast to traceelement measurements, there are reasons to expect that some deposits(those 'conformable' deposits which more or less correspond tosingle-age models of emplacement) will have a narrow range of isotopicvalues; but this can only be discerned by systematic sampling.Characterizing deposits by terming some measurements'outliers' and then igoring them is simply bad science. So itis that the failings of the lead isotope methodologies proposed by Sayreet al. (1992) and the sub-fields suggested by the Oxford group inresponse (Gale & Stos-Gale 1992) are the same as those whichafflicted af��flict?tr.v. af��flict��ed, af��flict��ing, af��flictsTo inflict grievous physical or mental suffering on.[Middle English afflighten, from afflight, the SAM study. The groupings - trace element or isotopic -created by this form of analysis are essentially statistical artefactswhich may or may not coincide with entities that have geological orarchaeological integrity. The SAM group (incorrectly) assumed thatartefacts which were statistically associated in terms of their impuritypatterns must derive from the same source, and that artefacts fallingoutside the group must be derived from a different source. TheBrookhaven/Smithsonian group have (incorrectly) assumed that ores (andslags) which are statistically associated in terms of their lead isotopecomposition must derive from the same source, and that those fallingoutside the statistical group must be derived from a different source.With the collapse of the simplistic sim��plism?n.The tendency to oversimplify an issue or a problem by ignoring complexities or complications.[French simplisme, from simple, simple, from Old French; see simple provenancing approach, thechallenge for researchers today is to develop a framework for thearchaeological interpretation of lead isotope data in which thelimitations imposed by geology or by the complexity of metal productionand use are acknowledged and freely discussed. This discussion must notbe the exclusive preserve of a restricted group of archaeologicalscientists, for the answers,involve integrating archaeologicalinformation to the greatest possible extent. Kept apart, the isotopedata will never yield meaningful patterns.A new framework for metals analysisThe question of how ore deposits can be defined in geological orchemical terms begs a profound question: 'what constitutes an oresource for prehistoric metallurgy?' So far, ore sources have beenconsidered in terms of islands or large mainland deposits, but thisconcept is breaking down. The attempts by the Brookhaven/Smithsonian andOxford groups to sub-divide the Cyprus field into component parts hasbeen discussed (see above and Budd et al. 1995). Unfortunately, therelationship between the lead isotope ratio of an ore deposit and itsgeographical location is complex. It does not necessarily follow thatdeposits which are close together will have similar compositions. Webelieve it is not useful to attempt to characterize individual mineswithin a metalliferous region such as Cyprus for archaeological as wellas geological reasons. Current data show that individual Cypriot mineshave ranges of lead isotope ratios which overlap one another (Budd etal. 1995a), but even if they could be accurately resolved there arefurther objections. There are specific localities at which coppermineralization would have been accessible to ancient miners, but thenumber of potential sources is vast. Outcrops insignificant in moderneconomic terms could have yielded plentiful resources for ancientproduction. Ancient mining localities may have been destroyed bysubsequent activity or worked to the extent that representative mineralsare no longer available to be sampled. It is impossible to know whetherone has measured all the possible ore sources in a region and highlylikely that one has not.The whole concept of metal artefacts being derived from a single rawmaterial source is problematic in the complex craft and trading world ofthe Late Bronze Age Aegean in which metals are accumulated in bulk andtransported long distances. Such ideas are a relic of analogies withmodern industries based on particular raw materials, utilising aspecialist work force and specific technology. These views are now beingindependently rejected as a model for prehistoric metal-working(Sherratt 1994; Budd & Taylor 1995; Budd et al. in press). Webelieve that it is more reasonable to see oxhide Ox´hide`n. 1. The skin of an ox, or leather made from it.2. (O. Eng. Law) A measure of land. See 3d Hide. ingots as part of abody of smelted copper which might well have been made from rawmaterials from more than one source. This idea, discussed at lengthelsewhere (Budd et al. 1995a; 1995b), can explain the relatively tightrange of lead isotope compositions of the ingots and their distributionon bi-variate plots, centring towards one side of the Cypriot field. Inany system involving the random mixing of primary smelting products fromdifferent sources, any degree of weighting (such that one source tendsto introduce more copper and another less and so on), will result insecondary material which has a smaller range of lead isotope ratios thanany of the individual source groups. If significant recycling is theninvolved in artefact See artifact. production, the cluster of values will be tighterstill. The position of any such cluster will be somewhere between thoseof the various sources, depending on their relative contributions. Theproblem is that it will not be possible to know where all the sourcesmay have been, or even if they are all represented by the availablemeasurements. Extracting the component parts from such a system might bevery difficult.Clearly, as happened with trace element analysis, the application oflead isotopes to provenancing archaeological copper alloys is becoming aproposition far more complex than was initially anticipated. Where thelimits of variation of a given ore body are fully defined, any artefactwhich does not fit within the bounds of the field and its attendantexperimental errors is known to derive, at least in part, from materialfrom elsewhere. The inescapable difficulty is that an artefact thatfalls outside an ore source field is not necessarily wholly derived fromanother ore. If one has independent evidence that the group of artefactsunder investigation were produced from a single source, then it may bepossible to draw conclusions regarding locations from which they did notcome. In more complex - and perhaps more usual - situations, largequantities of copper would have been in circulation over areas with morethan one raw material source; then it may never be realistic to expectlead isotope or trace element measurements to assign provenanceunambiguously. Analytical data might be able only to exclude sourceswhich are highly unlikely to have contributed significantly to themetalwork under investigation. Perhaps the whole concept of provenanceis redundant as far as prehistoric metals are concerned. Why should weexpect, in the complex later prehistoric world, that each object wasmade from copper extracted only from a single locality and that, onceproduced, copper alloys were never re-used? The complicated fabrication fabrication (fab´rikā´shn),n the construction or making of a restoration. history and widely scattered iconographic i��co��nog��ra��phy?n. pl. i��co��nog��ra��phies1. a. Pictorial illustration of a subject.b. The collected representations illustrating a subject.2. influences attested inspectacular later prehistoric metalwork like Denmark's famousGundestrup cauldron The Gundestrup cauldron is a richly decorated silver vessel, thought to date from the La T��ne Period in the 2nd or 1st century BC. It was found in 1891 in a peat bog near the hamlet of Gundestrup, in the Aars parish in Himmerland, Denmark ((Taylor 1992) argue persuasively against that narrowview.There are ways forward. The Heidelberg/ Mainz group have explored thecombination of lead isotope with trace element data to achieve betterdiscrimination between raw material sources, but have always acceptedthat this would not work if recycling and metal mixing were commonplace(Pernicka et al. 1984). There is some hope that other isotopic systemsmay indicate the extent of recycling (Budd et al. 1995c). Perhaps thelong-term answer, however, is to change the question. The oxhide ingotsof copper that now look less attractive for provenance studies remainjust as important to the study of Bronze Age production and trade (Knappin press). This observation is underlain un��der��lain?v.Past participle of underlie. by a crucial point:provenancing is not the only way in which to study the organization ofprehistoric metal production and use. Perhaps detecting change in thepattern of metal procurement and use is more useful than assigningprovenance. Knapp (in press) has observed that some 30% of the analysedmetal finds from a large number of Late Bronze Age Cypriot sites havelead isotope ratios inconsistent with the Cyprus field and suggests thatmixing and re-melting of metal - for which there is also evidence fromcoeval co��e��val?adj.Originating or existing during the same period; lasting through the same era.n.One of the same era or period; a contemporary. 'foundry' hoards - may have played a role in this.Putting this together with the proposal that some oxhide ingots may havebeen made from copper originating from more than one location, he goeson to speculate over the possible implications for the development ofLate Bronze Age social organization. In this view recycling and thepooling of copper from multiple sources is seen not simply as aback-projection from our contemporary ideas, but as genuinelyrepresented in the material record, suggesting social interactionsacross cultural borders in the development of a regional economicsphere. Late Bronze Age metallurgy is seen as a complex system in whichmultiple sources feed into a koine of stock material circulating byvirtue of trade, through exchange and perhaps inferring the interventionof developing regional political and/or magico-religious authorities.As with the large-scale trace-element analytical programmes thatpreceded it, lead isotope analysis has brought us some way towardsunlocking the question of provenance, but definitive answers elude e��lude?tr.v. e��lud��ed, e��lud��ing, e��ludes1. To evade or escape from, as by daring, cleverness, or skill: The suspect continues to elude the police.2. us.Lead isotope ratios will, and should, continue to be measured as part ofarchaeometallurgical research programmes, but a more flexible approachto their interpretation is required. In particular there is a need tore-evaluate the emphasis on provenance and to develop a framework bettersuited to the analytical tools we have. This requires a clear dialoguebetween analysts and the field-workers they support in an environment ofrigorous scientific review of approaches and methodologies. Thesechanges are likely to come about naturally as the days become numberedfor 'large equipment' facilities for the sole support ofarchaeology, but scientists must not be allowed to develop an arrogantmonopoly in the interpretation of analytical data. Archaeologists mustbe directly involved in this and in the formulation of relevant buttestable hypotheses which move beyond the tired old idea of provenance.A reliable base of data from lead isotope determinationsIn a welcome development since this paper was first drafted, theeditor of the journal Archaeometry has undertaken to provide a rapidmethod of publication for archaeological lead-isotope data in a similarform to the, now familiar, radiocarbon date lists. We feel sure thatthis will help to clear the current backlog of unpublished measurementsand hope that it will result in a comprehensive and reliable database tofacilitate the wider interpretation for which we have argued.The Archaeometry database is intended, for the deposits covered, tobe a definitive statement of what is regarded as current reliable datafrom the Isotrace Laboratory in Oxford (Gale pers. comm.). Themeasurements tabulated in the first publication in the series - on oresfrom the western Mediterranean (Stos-Gale et al. 1995) - are a mixtureof new and previously published analyses. Some previously publishedsamples are omitted; some because they are only single measurements fromotherwise uncharacterized deposits for which more data are expected, andsome because they have been rejected until re-measured on grounds ofprecision, possible contamination and instrument problems (Gale pers.comm.). The specific criteria for data selection are not always madeclear in this initial paper, but publication of an explanation of theguidelines underlying data selection and of more, recently acquired,western Mediterranean ore data is anticipated in the near future (Galepers. comm.).We strongly support this effort to produce a straightforward andreliable database of lead isotope measurements for ore deposits ofarchaeological interest. Clearly, it is advantageous to remove bad orsuspect data in the construction of ore fields and we are pleased tonote that a comprehensive re-measurement programme is now under way atOxford with this objective. There is, however, a danger that thetemporary omission of data from some deposits, pending further or repeatmeasurements, will lead to a false impression of the overall spread ofdata from a region; suggesting a more limited field for the region thanis actually the case. We note, for instance, that one immediate effectof the omissions from the new Sardinian database is to create theimpression of smaller, more discrete, field with only a few outlyingsamples. We are confident, however, that any danger of misinterpretationcan be avoided by comprehensive sampling and analysis and we lookforward to the further publications which are promised.Acknowledgements. Two of the authors (PB and BS) are supported by theNatural Environment Research Council (UK) and one (RGT RGT RightRGT Register(ed)Gross TonnageRGT RegimentRGT Reliability Growth TestingRGT Remote Ground TerminalRGT Radioisotope Thermoelectric GeneratorRGT Rich Guy's TelescopeRGT Requirements Growth Testing ) by theAustralian Research Council. Many thanks to Tim Taylor and referees formany helpful comments and suggestions on earlier versions of thismanuscript.ReferencesBEGEMANN, F., E. PERNICKA & S. SCHMITT-STRECKER. 1995. 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