Internet Archaeol. 17. Willis. Case Study 2: ratios between Drag. 29 and Drag. 37 decorated bowls

5.3.2.4 Case Study 2: ratios between Drag. 29 and Drag. 37 decorated bowls

This approach may be undertaken for decorated samian types, but only meaningfully in the later 1st century, and specifically in respect of the ratio between the bowl forms Drag. 29 and 37, as the later gradually replaces the former (e.g. Dickinson 1992a; Mills 1999; Hartley 2000).

In the case of the canabae outside the fortress at Caerleon (1984-90) Brian Hartley used the ratios among South Gaulish La Graufesenque Drag. 29s and 37s at three locations (taking all contexts, i.e. not by phase or stratification) to gauge the start date of the settlement. At the Riding School Field site the ratio was: 15:85 (15-85%), at Cambria House this was 6:47 (11.3-88.7%) and at Smallholding, the figures were 5:21 (19.2-80.8%). These figures are remarkably similar, with the aggregate being 26:153 (14.5-85.5%). Bearing in mind that Caerleon, as a military site, is likely to have received regular supplies of samian and be more 'up to date' than civil sites in its samian assemblages, these figures suggest a start date for the canabae very late in the 1st century.

In her report on the samian from the annex ditch of the first Flavian fort at Tullie House, Carlisle, Dickinson (1992a, 52) examined the ratio of (La Graufesenque) Drag. 29 bowls to 37s in order to assist in dating the deposit. The ratio happened to be 1:1. Noting that the 29 was apparently not made after c. AD 85 she observed that the deposit would have had to have occurred before the form had ceased to be in common use, before the dominance of Drag. 37. She compared the ratio with those for sites known to have been occupied for a short duration in the 80s, such as the military site at Camelon. She pointed to a similarity between the annex ditch ratio and equivalent ratios from other sites on the northern frontier dated to this period (1992a, 52). Other recovered evidence also pointed to this date in the mid 80s (Caruana 1992). The database shows that parity is reached between the two types at exactly this time, specifically between AD 87 and AD 89; thereafter Drag. 37 becomes markedly more common than Drag. 29 (compare SGLG 29 with SGLG 37). The Flavian Cala Culip IV wreck has a similar ratio of 1:1 for these forms, though a date before c. AD 80 has been suggested (Millett 1993b). This is not necessarily inconsistent, as wrecks represent a specific type of deposit among which we might expect to find early examples of items (cf. Millett 1987b).

Drag. 37 becomes a more frequent find than the Drag. 29 after c. AD 90, though there are important differences in frequency relating to site type, in so far as civil centres may have a slower turnover of samian pottery, with 'valued' samian vessels, such as the Drag. 29 being curated over time; hence the type of site from which an assemblage derives needs to be borne in mind when undertaking this analysis (discussed below, Section 5.8.2; cf. Appendix 5.1; cf. Groves 1993, 127).

Table 5 shows the relative proportions of Drag. 29 and Drag. 37 bowls in a sample of specific stratified groups (as available in the literature) during the second half of the 1st century and beginning of the 2nd century AD. This table demonstrates the shift in frequency from Drag. 29 to 37 over time, providing a different perspective on the same trend seen in the database. Few samples were available for smaller civil centres and rural sites, mainly because groups of samian of this date from these sites were so small. Table 6 presents the same data but in this case it has been calibrated. Table 6 is discussed in Appendix 5.1.