7.2 The frequency of samian at different site types

7.2.1 Background, the sample and trends

Quantitative approaches to the composition of pottery assemblages and groups of the Roman period (Young 1980a; Fulford and Huddleston 1991) have greatly enhanced understanding of patterns of supply and consumption, and are now standard (e.g. King and Millett 1993). It is only in recent years, however, that sufficient studies have come through to publication to facilitate comparative analysis of the proportions of types and wares occurring, for instance, over time and between sites. Quantitative information on the incidence of samian was noted to be particularly rare by Fulford and Huddleston (1991, 38), but since 1990, more data of this type has become available. Nonetheless, securing appropriate samples of quantified samian information from stratified deposits for like-with-like comparison is not straightforward. The varying circumstances of material and assemblages, and differences in approaches to its reporting mean that information on samian occurring at sites is published in a diversity of ways. The recently published volume on the pottery from the Castleford fort and vicus is, for instance, quantified by sherd count and vessel numbers, not by weight and EVE (Rush et al. 2000), hence it cannot be employed in this comparison (though numbers of forms present by phase are listed and so can be used). Methods of quantifying samian for reports vary, and reporting is not standardised (often because the nature of the assemblage or of archaeological recovery do not lend themselves to standardisation). These circumstances are, of course, commonly encountered in most comparative studies in archaeology. It has been possible, though, to collate large samples of stratified data on the incidence of samian within stratified pottery groups.

It was decided to collect information on the presence of samian within groups by two standard methods, namely by weight and EVE, in line with the samples collected for Phase 1 of the project. Both weight and EVE (estimated vessel equivalents) are considered to be good measures of the comparative frequency of pottery types (Orton 1989; Fulford and Huddleston 1991; cf. Willis 1998a). In most cases EVE is by rim equivalence (or RE). Amphorae were excluded from the analysis since they were primarily transport containers, and therefore different from 'kitchen and table' pottery; besides, their massive character gives rise to heavy sherds, while their narrow mouths allied to thick walls often result in rim sherds with unusually large proportions of rim circumference present: the sporadic presence of either body or rim sherds in contexts can thus distort weight and EVE data, and in turn comparative analysis.

In assembling data on the proportions of samian present within pottery groups for this study the aim was to establish the degree to which these proportions reflect the character of the site (as established by other archaeological indicators, such as site size, layout, nature of structural remains, coin list, etc.) from which the groups were recovered. Since several indicators show that samian was particularly prized, that samian vessels were likely to be of some value, and that it had a distinct cultural resonance (cf. above) the incidence of low or high proportions of the ware within stratified groups may be considered an index of the status, exchange connections and identity of sites. Degrees of variation are to be expected in the composition of pottery and other types of archaeological assemblages as these result from combinations of factors (e.g. Millett 1980; 1987a; cf. Lambrick 1984). Chronological period and site type are often strong determinants in this respect. The samples are arranged in terms of these variables. In examining these groups it is thought likely that the proportions of samian present within stratified groups are an approximate guide to the level of supply and consumption of samian ware vis a vis these sites. Events and practices can, of course, 'distort' or impact on this relationship, for instance via curation of certain vessel types, approaches to rubbish disposal, and structured deposition. The collected samples by both weight and EVE show a general patterning evidently relating to the category of site from which they derive. Divergence from the general pattern will be of interest as such cases may highlight significant aspects of sites and require explanation.

For the paper publishing the results of Phase 1 of the project it was possible to assemble data on the proportion of samian present within some 56 stratified groups by weight and 30 where EVE was the measure (Willis 1998a, Tables 1 and 2). The coverage of the 1998 samples was fairly balanced in terms of site type when weight was the measure (Table 20). In the case of measurement by EVE, the fewer samples were mostly from the major civil centres and smaller centres (e.g. London and Chelmsford) with hardly any available at that time from military sites, extra-mural sites outside military establishments or rural sites; this was largely a function of the time lag between the institution of EVE as a routine measure in the late 1980s and early 1990s, and the publication of reports. It was possible to collect many more samples by EVE for the present study, and to extend the number when weight is the measure (Tables 21 and 22). These sets of samples should, accordingly, provide a fairly robust, reliable guide to the relative frequency of samian at sites in Britain.

The samples published in 1998 showed that there was a marked difference in the frequency of samian at both military sites and major civil centres on the one hand (where samian accounted for almost 10% of the pottery by weight) and, on the other, the smaller civil centres (including Small Towns and roadside settlements), rural sites and religious foci (mainly in the countryside, or settlement outskirts), where the frequency was very low. The pattern endured independent of chronological period. Table 20 summarises the data from 1998 by averaging the percentages of samian present per group by site type (Willis 1998a). This 'short-cut' makes clear the gross difference in supply and consumption between these sites. This difference appears emphatic. It is perhaps not inconsistent with what might have been predicted, but this type of data had not been brought together previously and so demonstrated a trend for the first time. Inevitably, scrutiny reveals differences between particular sites within the same category (cf. Willis 1998a, Tables 1 and 2). The assembly of an enlarged sample of quantified groups was considered important in order to verify the trends suggested in 1998.

Table 23 catalogues samian as a percentage within groups by weight, with the groups arranged by site type and alphabetically for ease of reference. Table 24 arranges these same groups into chronological order by site type for comparison. Turning to EVE, Table 27 lists groups where EVE is the measure of the frequency of samian within groups, in this case arranged alphabetically within site type. Finally, Table 28 arranges the groups appearing in Table 27 by date. An assessment of these tables shows that the enhancement of the sample underscores the general pattern: that proportions of samian (that is to say its frequency) varies by site type.

Note that the frequency of samian within groups usually appears higher when EVE is the measure, when compared to measurement by weight. This arises from the nature of samian, since as a fine ware it tends to be thinner walled than some coarse ware types, and on the whole samian cups and dishes, etc. weigh less that other pottery types. All pottery forms have a maximum rim equivalence of 1.00 (i.e. 100% of rim circumference) but some forms weigh much more than others: samian vessels are rather light when considered alongside other contemporary types and so measurement by weight, while very useful for inter-site comparisons, tends to depress the presence of samian in terms of proportions of vessels. Hence the difference is explained by the comparatively low weight to EVE ratio of samian relative to many other pottery types.

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