A RESISTIVITY SURVEY OF THE PRESUMED ROMAN GASK TOWER AT PEEL, PERTH & KINROSS
D J Woolliscroft
The Site
Peel lies at NO 06042323 (illus 1), c. 4km to the west of Perth
and stands at the southern edge of a heavily ploughed field with no surface indications. The site was discovered from the air in 1986 by G.S.Maxwell (RCAHMS neg: PT/15159) as a clear penannular ring ditch, with its southern side slightly truncated by an open field drain, and with a single entrance break on its northern side. It has yet to re-appear in any subsequent season and no further work has been done. The immediate surroundings contain a significant concentration of pre-historic monuments, notably the henges at North Blackruthven (NO 068246), the Marlefield barrow field (c. NO 056243) and the large Huntingtower tumulus (NO 069249), but the site has been, at least tentatively, proposed as one of the Roman Gask frontier watchtowers since its discovery (Frere 1987, 309). This is certainly a plausible interpretation. Its form seems right, at least for this northern part of the system where the towers have only a single ditch and, as no central cist or pit was visible, it seemed unlikely to represent a barrow. Furthermore, its entrance faces the line of a long double pit alignment (running from c. NO 060240 to c. NO 082250) which runs at a lower level along the same valley side and which probably represents a series of quarry pits marking the course of the Roman road from the Gask Ridge to the Tay. The site is, however, significantly further from the road than any other known Gask installation (c. 875m) and so, assuming that the identification of the road line is correct, the site cannot safely be assumed to be Roman simply on the evidence of a ring ditch.
The site stands on the 70m contour some way up the southern side of the Pow Water valley but, although only 35m above stream level, it enjoys superb views in all directions and especially across the entire 180o sweep to the north. Even to the south, however, where it faces gently rising ground, the view still stretches for several kilometres in places and would have been greater still from the full likely height of a Roman tower. In particular, the site is intervisible with the Roman towers of Westmuir and West Mains of Huntingtower, along with the temporary camps of Easter Powside and East Mid Lamberkine, although the fort of Bertha probably lay just out of sight.
The Resistivity Survey
As a non destructive means of obtaining additional data, the Roman Gask Project conducted a resistivity survey in October 1999 (illus 1). The ring ditch and its entrance gap showed clearly on the resulting plot, although there was a slight weakening towards its southern side, where the line is masked by the field headland and possibly by upcast from the modern drain. The site had appeared rather small from the air, perhaps no larger than 16m across (although the RCAHMS oblique photograph contained too few registration points to be properly rectified) and this was confirmed by the survey. The ditch proved to average c.15.7 m in external diameter, although it appears to be slightly elongated along the entrance axis. Where it shows most clearly, the ditch is probably in the region of 2m wide, with an entrance break of around 3m. Unusually, despite the fact that the site showed from the air as a positive crop mark, the ditch appeared as a series of high resistance readings, rather than as low readings as is more usual. This phenomenon is far from unknown, however, especially on sites where the ditch backfill is more free draining than the natural subsoil (or where it contains a significant quantity of stone) and the nearby Roman tower of Huntingtower showed an identical pattern (Woolliscroft, forthcoming 1). There was no trace of an upcast mound outside the ditch, although this may have been completely ploughed away, and again there was no sign of a central cist. There was, however, a band of high readings running north from a point on the ditch c.5m west of the entrance break, whilst a second heads roughly north-east from a point c. 5m east of the entrance. It is possible that these could represent additional ditches which might form part of an outwork of some kind for, although the air photograph shows two modern land drains heading for exactly these points, neither feature could be tracked by resistivity running across the ring ditch interior.
Discussion
If identified as a tower, the site would be the smallest currently known on the Gask system. Indeed, it is even slightly smaller than the inner ditches of some of the more southerly double ditched towers (which average 15.75m in diameter). Nevertheless, it is only c. 0.5m smaller than its eastern neighbour, West Mains of Huntingtower, which is itself unusually small (c. 15.7m as against 16.2m), and, as its ditch width and entrance break size are also similar to Huntingtower’s, the site does appear consistent with the tower design of this particular part of the frontier. The lack of any central pit would certainly make an identification as a barrow unlikely and the ditch appears somewhat substantial for a round house. The site is also almost exactly 1 1/3 Roman miles from Huntingtower and 2 2/3 Roman miles from Westmuir, the closest known Gask tower to the west, which might suggest a 2/3 Roman mile spacing for the sites at this end of the line, in contrast to the 3/5 Roman mile spacing detected amongst the southernmost sites. Nevertheless, although on present evidence an identification as a Roman tower does appear much the most likely interpretation, it cannot be regarded as proven, especially given the possibility of an outwork, and only excavation will settle the matter for certain. In particular, it is a matter for concern that the site appears to lie so far from the Roman road. To date the only Gask tower known to lie at any distance from the road is Raith, but even this site is only c. 160m from the line and has obviously been located to exploit an exceptionally good lookout position, whilst the road follows easier ground. It is possible, however, that the road at Peel may have run much closer to the site at some point during the Roman occupation. For a number of air photographs (notably RCAHMS A36244 and A41264) have shown the faint track of what appears to be another road running in a perfect straight line for 2 1/4 km from NO 044212 to NO 058230, and, if projected, this line would pass less than 50m to the northwest of the site, which would be a far more typical distance. There has already been speculation (T.M.Allan, Pers Comm) that the known, well constructed, Roman road in this area (which appears to be the line associated with quarry pits) might be an Antonine feature, and that this faint, apparently lighter, trackway might have been the original Flavian period road. If so, then this would have been the contemporary route during the occupation of the Gask towers, which would make a Roman identification for Peel appear still more likely. It must be stressed, however, that there is as yet no firm evidence to support this theory for, however attractive it might be in the current context and, despite the fact that the writer has offered a similar hypothesis to explain an apparent loop road at the tower of Shielhill North (Woolliscroft, forthcoming 2), no dating evidence has ever been recovered from either this route or from any part of the known Roman road on the Gask. There can thus be no guarantee that the trackway is Roman at all which means that, for the moment, it seems safest to leave both it, and ultimately the identification of Peel, open to doubt.
Acknowledgements
The writer would like to thank Mr M.A.Hall of Perth Museum for his help in the field and the Dupplin Estate, their factor Mr J.M.Smith and their tenant Mr A.Simpson for allowing access to the land.
Bibliography
Frere, S.S. 1987. “Roman Britain in 1986”. Britannia, 18, p309
Woolliscroft, D.J. forthcoming 1. “The Roman Gask Series Tower at West Mains of Huntingtower, Perth & Kinross”, Proc Soc Antiq Scot.
Woolliscroft D.J. forthcoming 2. “The Roman Gask Series Tower At Shielhill North, Perth & Kinross, Including Excavations By The Late Professor J.K. St.Joseph”, This vol