Signalling and the Design of the Gask Ridge System D J Woolliscroft*
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Proc Soc Antiq Scot, 123 (1993), 291-313 Signalling and the design of the Gask Ridge system D J Woolliscroft* ABSTRACT This paper attempts describeto signallingthe arrangements along Gaskthe Ridge, Strathin Earn, and the influence that these may have had on the general layout of the system of Roman installations, in an effort to understand the purpose and context of the Roman line. It also re-excavationreportsthe on possiblea of Roman fortlet within metresGaskthe of Ridge tower of Midgate (NO 02112047). This juxtaposition suggests that the Gask Ridge fortlets may not be exactly contemporary with the towers. Although, for the moment, there is insufficient evidence proveto thatfortletsthe belong anotherto Flavian a phase, to or different period altogether, former the still may appear more likely. INTRODUCTION Scientific study of the Gask Ridge began at the turn of the century with the excavation by D J Christison (1901e fortleth f f Kaimo o )t s Castl e eigh somd th an f et o ewatc h towers then known on the Ridge itself. Although a great deal was learned through this programme, none e siteoth f s yielded dating evidenc ee shal w and s l a ,see e excavatioth , e fortleth y f o ma nt have been flawed. Since then, another fortle coms ha tligho t e t Glenbana t k (Maxwell 1990), to the south of Ardoch, along with evidence for 10 new towers, bringing the number known or suspected1 to 18 (illus 1). The towers can also now be seen to fall into two distinct groups, although the significance of the change is uncertain. For, whilst those to the north of Kaims Castle, includin gGase thosth kn o eRidg e itself, hav singlea e surrounding ring ditch, those further south have two. Furthermore a singl, e stratified Flavian sherd from Gask House (Robertson 1974, 20) and a possible second from Westerton (private communication), both in e northerth n group, have finally provide probabla d e date for t leasta , e singlth , e ditched towers, whilst the discovery of the Flavian fort at Doune has suggested a possible destination for the southern end of the system (Maxwell 1984). picturA e has, thus, bee integraten a n f builo p u t d Flavian system, stretchin t leastg(a ) fro Teite mth t Doun ha Bertho Taye t fortlete th th ;n a o f Glenbano s Kaimd kan s Castle have usually been seen as part of this system, despite their current total lack of dating evidence.2 With this much apparently settled debate th ,s move consideo ha t e n d o exace th r t contexn i t which the system was built. For example, some scholars would argue for an early date, with the line forming part of the provisions made during Agricola's fourth season (Hobley 1989, 73-4lated an r) replace glen-blockine th y db g forts. Others suppor latea t r date, wite th h Holwoo4 2 * d Drive, Manchester TOWER-SINGLE DITCH TOWER-TWIN DITCH ILLUS 1 The Cask Ridge system WOOLLISCROFT CASE TH : K RIDGE SYSTEM 293 system representing an attempt to hold a frontier line defending Fife in the aftermath of the abandonmen f Inchtuthio t rese f northerth o t d an l n Scotland (Breeze 1982, 61-5). Case alsn made ca sob r regardinefo e Casa 'bacg th s ka k stop' frontier r whicfo , e hth glen-blocking forts served as outposts, or for seeing the glen-blockers as the true frontier wit e Gashth s merelka closela y y watched road supervisin e strategigth c invasion route through Strathearn (Pitts & St Joseph 1985, 278). Yet, despite the fact that three of the four systee th fort n mo - sArdoc h (Breeze 1983), Strageath (Frer Wilke& e s 1989 Berthd an ) a (Adamson & Gallagher 1986) - have Antonine as well as Flavian occupations, the assumptio more n th tha l e al tmino r installations belon singla o gt e Flavian lins persisteeha d throughout these discussions. If this was the case, we would appear to have a fairly logically laid out system. The presenc f Glenbaneo k between Doun Ardochd ean Kaimd an , s between Ardoc Strageathd han , suggest alternatinn sa g serie f fort t fortletsalono d ou an roas e intersperset d gth dse san d with a closely spaced serie f watco s h towers. Attempt fino t s d signregulaa f o s r tower spacing interval ,e Romabaseth n o dn mile (Rivet, 1964, 196-8), have never proved wholly convincing t thi(Tablbu s , neee1) d hardly surpris irregulae vien th i f s wo eu r tower spacings contemporare onth y Wetterau Limes e nortth f Frankfurho o t , Germann i t y (Woolliscrof& t Hoffmann 1991). TABLE 1 Gask Ridge site spacings Glenban 230k- c Greenloanin 0 m g Greenloaning - Ardoch c 2750 m Ardoch - Blackhill Wood 900 m Blackhill Wood - Shielhill South 875 m Shielhill Sout h- Shielhil m 0 95 l North Shiehill North - Kaims Castle 875 m Kaims Castle - Westerton 2300 m Westerton - Strageath c 4200 m Strageat h- Parkneu k 1750m Parkneu k- Rait h 1520m Raith - Ardunie 1510m Arduni e- Roundla w 1110m Roundlaw - Kirkhill 960 m Kirkhill - Muir o' Fauld 1440 m Muir o'm Faul0 87 d- Gas k House Gask House - Witch Knowe 800 m Witch Know e- Mos s Side 1120m Moss Sid e- Midgat e 1400m Midgate - Westmuir c 915 m 397c 5m Westmui r- Pee l Peel - Huntingtower c 1940 m Huntingtowe 317c 5m r- Berth a It is, however, apparent that the system as we have it today cannot be complete. Glenbank is not intervisible with Doune and, although Huntingtower would, from its likely original tower height, have been visible from Bertha, both spacing and signalling considerations suggest that further towers await discovery at both ends of the line. Other obvious gaps exist between Westmuir and Peel, Westerton and Strageath, and Greenloaning and Ardoch, whilst a number of smaller gaps (Table 1) might also repay attention. At one time it also seemed likely that the system continued south, beyond Doune, perhap Flaviae th o st n for f Camelono t well-preserveA . d hilring-ditcp to l t Wesha t Pleano t , | SOCIET 4 29 ANTIQUARIEF YO SCOTLANDF SO , 1993 the south of Stirling, was once interpreted as a tower of the Gask Ridge type (Crawford 1949, 18). This has been shown to be non-Roman (Steer 1956),3 however, and all that can now be sai thats di , whilst extension e soutth f Douno ho st , indeed norte or th f Berthho o t , a cannot rulee b d out, therfiro n ms ei evidence that they existed. THE SIGNALLING SYSTEM Despite these gaps in our knowledge, it is possible to reconstruct at least a skeletal signalling systee Gasth r km fo Ridge s currentla , y understood, base a stud n f eacdo yo h installation's field of view, from its likely full original height (Woolliscroft 1989b). As all long-range Roman signalling relie n visuado l techniques (Leiner 1982), direct communications could take place only between intervisible sites readee Th . s cautionei r d fro outsete mth , however, that suc hstuda shon yca w only wha possibls t wa bestta , ,eor likely. Signallin procesa s gi s that leaves little physical trac attracted ean d scant detailed comment from ancient writerst I . must always be remembered, therefore, that the fact that a signalling system was apparently both possibl desirabld ean givea n eo n Roman deployment doe t necessarilsno y mean thay an t such system actually existed. That said, there are design oddities on a number of Roman frontiers that see mmako t e sense onl s movea y o accommodatt s e signalling (Woolliscroft 1989a; Woolliscroft & Hoffmann 1991) so that some signals provision does appear likely on manyt all f Rome'no o , f i , s major military systems. e knowth Almos f o n l Gasal t k Ridge installation e intervisiblar s e with bot f theiho r immediate neighbours casew fe se wherth n i ;t (Westmuir e no the e yar r instancefo , , cannoe b t seen from Peel), it already seems likely on spacing grounds that the sites are not true neighbours, as intermediate towers may still remain to be found. It should, therefore, have been possibl paso et s signals from towe toweo t r r along t leasta , ,e line mosth f . o Indeedt , mutual intervisibility between neighbours seems to have been regarded as important and, as Wetterae onth u Lime Germanyn si , ther signse ear thairregulae th t r inter-site spacings areo t , some extent, causeneee th ensurr o exampledt y db Fo . eit , ther tendencya s ei , especialln yo the Gask Ridge itself, for the towers to be sited on or near pronounced changes in the angle of grounde slopth f fiel e e o limie tha o f vieth s ,on dth o f numbe a tt f o t wa o t se f site ro e sar or othe f theio r r neighbour appeao s d thein o an rs r skyline. Where th e cas th n thi o es i s Ridge itself, it is usually a site's eastern neighbour that marks the limit of its vision, which suggests thasystee th thav y mma e been lait fro weste dou m th . Indeed pronounceo s , s thidi s tendency, tha t becomei t s first-tima eas r yfo e visito locato t re groun th e site eth n o sd with little help from a map.