The Antonine Wall Distance Stones are a rich epigraphic resource (Breeze 2015, 69) that provide invaluable insights into the construction of the mural barrier with explicit reference to distances constructed by the three Roman legions tasked with building the frontier infrastructure: Legio II Augusta, Legio VI Victrix and Legio XX Valeria Victrix (Keppie 1998, 72–90). Dedicated to the Emperor Antoninus Pius, they form a tightly dated body of epigraphic evidence. Many also contain decorative details and sculptural reliefs depicting legionary symbols as well as scenes of battle, the capture of indigenous warriors, religious practice and deities (Breeze and Ferris 2016). Nineteen of these monumental inscriptions are currently known, including a plaster cast of one lost in a fire in Chicago. Of these, 16 and the plaster cast are in the collections of the Hunterian Museum, one is held by Glasgow Museums and another is in the collections of National Museums Scotland. They constitute a unique body of monumental inscriptions that were originally adorned in vibrant colours to bring the various scenes to life and recent research has physically and digitally reconstructed the pigments used (Campbell 2018; Campbell 2020a and b). There is scope for further analysis of the Stones, particularly any new ones that may be recovered in future (see Applications of scientific techniques).
Several have cramp-holes carved in their rear, confirming they were embedded into a frame or platform (Keppie 1976, 2). It has been suggested they were erected at each end of a building sector, possibly on both north and south sides of the rampart. One possible candidate, the stone platform discovered at the rear of the Wall at Tollpark, has been rejected as a possible example of such a supporting structure because of its large size (Keppie and Breeze 1981, 240). The Stones detail very precise lengths of building work by each legion, which implies careful subdivision of labour, and two actually specify that a rampart (vallum) was being built (Keppie 1998, 50–6).
Most Distance Stones have been recovered from a four-mile stretch of the Wall’s western extremity (Castlehill to Old Kilpatrick). This implies the subdivision of work-sectors here into six smaller lengths, the constructed distances being measured in feet (P or PP for pedum/per pedum) west of Castlehill as opposed to paces (PER M/MIL P for per milia passuum) to the east (Macdonald 1934, 360–1). It is generally accepted that this subdivision was intended to hasten the completion of the Wall’s construction, indicating that this sector was built last (Keppie 1979, 7). This interpretation is supported by the stratigraphic evidence which demonstrates that all the installations in this sector were constructed before the rampart.
It is widely recognised that our interpretations are based upon a partial material record (Keppie 1998, 52). Indeed, it has recently been suggested, largely on statistical grounds, that the long-accepted interpretation of the changes in measurement recorded on the Stones from the western end of the Wall is not valid and, moreover, that they may actually relate to the building of the Military Way (Campbell 2020c). However, this view lacks adequate justification and is not widely accepted. Nonetheless, more examples potentially remain to be discovered, particularly east of Auchendavy where, except for a probable Distance Stone devoid of text from Arniebog near Westerwood, none are securely attested until the eastern terminus at Bridgeness.
- Instigate a targeted programme of ground penetrating radar (GPR) to seek additional Distance Stones focusing on the south side of the Wall and on either side of the Military Way.
- Be alert to the potential for the recovery of further Distance Stones, particularly to the east of Auchendavy.
- Take any opportunities to look for collections of dressed stones that may have served as platforms or frames for Distance Stones.
- Cease all cleaning of Distance Stones and ensure that any new discoveries are subjected to emerging non-destructive analytical techniques alongside micro-sampling to identify pigments and surface treatments (eg gesso).