Fort intervals

0 0.5 1 1.5 2 2.5 3 3.5 4

Figure 11.10. Intervals between the main installations of the Antonine Wall in Roman miles, measured between the north gates (or centre point, in the case of Bar Hill) as the crow flies.

long stretches of the linear works and, particularly, the Wall-top. A particularly fine example could be the proposed Tamfourhill Road fortlet, sitting at the junction of two long legs of the Rampart. In this connection, one is reminded of one of Poulter’s unexplained survey results. Both the Antonine Wall and Hadrian’s Wall are ‘composed of generally short lengths with, typically, equally good views in either direction at the turning points in between’ (2009: 117, my italics). From an operational viewpoint – one might think of surveillance, inspection, patrolling, whether along the base or on top of the Wall – such an arrangement would seem to make total sense.

What remains puzzling is the adherence of most fortlets to the 1-mile spacing pattern inherited from Hadrian’s Wall. John Poulter has suggested that ‘the only practical reason for such rigid marking-out would have been to divide the stretches to be patrolled along the Wall to be in equal lengths’ (pers.

comm.). However, the occasional – and wide – deviations from the 1-mile mark seem to speak against this explanation. What may be relevant here is an increased role for dispatch riders as a partial replacement of the complex, tower-based signalling arrangements of Hadrian’s Wall (Symonds 2018: 145). It has been suggested that the subsequent cobbling of the fortlets’ interiors may point to a change in their use (Keppie 1980: 110). However, such measures need not reflect more than ‘an acknowledgement of the necessity to protect the soldiers from mud’, certainly if these confined and ill-drained spaces were regularly trampled by horses (Graafstal et al. 2015: 61; Symonds 2018: 144). At Seabegs Wood, the Military Way serviced the fortlet’s south gate like its successor on Hadrian’s Wall would do with the milecastles. One function of the fortified frontier gates, then, may have been to serve as additional points of egress to the foreland. If so, this may have been a regressive element: most fortlets appear to have lost their causeways over the Ditch and some had their gateways narrowed or blocked at some point (Bailey and Cannel 1996: 344; Symonds 2018: 144), prefiguring later developments on Hadrian’s Wall.

If it is true that most fortlets were planned at a later stage in the planning process and with reference to a continuous system of Wall miles, this may resolve the old problem that the majority of the known fortlets are not situated somewhere midway between the two nearest forts, some of them not even nearly so, like Summerston. It would also imply the possibility of more than one fortlet ending up between two neighbouring forts. We have noted earlier that the chain of intervisibility requires an additional installation east of Bearsden – a potential twin of Summerston. In the long stretch from Falkirk to Rough Castle there is room for at least two fortlets, Watling Lodge and the proposed Tamfourhill Road site, with a possible third in the Bantaskin area.

The ultimate consequence of the two-tiered planning of the Antonine Wall is that the norm positions for fortlets could come into near collision with designated fort sites. Such a close encounter happened on Croy Hill, where the measured position of the fortlet was about 400m west of the main installation.

As it happened, the two ended up much closer than that. This is just one of many anomalies that justify a special section on this key site.

The Croy conundrum

On Croy Hill we are facing the following challenges, from east to west: a causeway over the Ditch without an appurtenant installation; a small fort (0.6 ha) c. 70 m to the west of incontestable secondary construction;

the fort’s east wall overriding a carefully constructed water feature with an overflow channel that passes under the Rampart; and, finally, c. 80 m west of the fort, a fortlet that was unquestionably built in

conjunction with the Rampart. With this state of affairs, Croy Hill has, understandably, become one of the cornerstones of the Gillam hypothesis since the discovery of the fortlet in 1977.

With regard to fort-fortlet combinations, three preliminary observations seem in place. Firstly, it may be noted that a fortlet has long been suspected in close proximity to Bar Hill, as this detached fort would have required its own guarded crossing through the linear works (Hanson and Maxwell 1986:

106). Secondly, we have just seen that close encounters between forts and fortlets could result from their different spacing systems. Thirdly, other Roman frontiers offer various examples of two types of installation in close proximity (cf. Breeze 2011: 201). In Upper Germany, there are several instances of a normal fort with an associated installation of numerus size, like Neckarburken and Walheim. At Stockstadt on the river Main, a fort was paired with two successive fortlets. The early numerus fort at the Saalburg now also appears to have had a fortlet (Schanze B) and an enclosure (Schanze A) next to it, possibly because of the local frontier crossing (Kortüm 1999: 200-2). In the Rhine estuary, Valkenburg had a fort and a fortlet guarding the two ends of the elongated military compound in the early Flavian period (van Dierendonck 1997: 549). In the Roman world, then, the juxtaposition of a fort and a fortlet may have been less cause for offence than in ours. Perhaps, teasing out the sequence at Croy Hill may help us overcome our intellectual resistance. We will start this exercise with a short digression on a rather overlooked essential.

Waterworks

Before work on fort defences could start there had to be a clear picture of the future flows of rain- and meltwater and, especially, sewage from the bath and latrine suite. On the Antonine Wall, bathhouses appear to have been planned initially inside the forts (Bailey 1994: 300), with the latrines usually attached to them and flushed with their waste water. For the discharge of all these water flows, channels had to be led through the stone base of the fort walls at the appropriate places. Unsurprisingly, the sanitary suites were typically planned in one of the fort corners, making good use of the lie of the land to channel all the sewage and waste water into one of the fort ditches or, even better, the Antonine Wall Ditch. For eight forts bar Croy Hill, we know the position of the primary bathhouses (Bailey 1994: 300 with fig. 1).

They were typically built close to the fort walls, either as a long row of rooms lying up against the fort rampart (Bar Hill, Westerwood, Balmuildy) or as a self-contained block typically relegated to one of the fort corners (Mumrills, Castlecary, Cadder, Old Kilpatrick). Six had their sanitary suites placed in the praetentura, five of which would have been able to discharge their sewage into the Antonine Wall Ditch, usually close to the corners of the fort. The same was true for Castlecary which had its bathhouse in the southeast corner, but a latrine in the corresponding north corner, again attached to the fort wall.

At Falkirk, careful arrangements for sewage disposal were made at the southwest corner of the fort.

Here, Geoff Bailey found a channel emerging from under the rampart, apparently crossing the two ditches over a small aqueduct before draining into the Goat Burn. At a later stage, a large settling tank was inserted on the berm of the fort wall, the sewer now forming an overflow (Hunter 2003: 303).

It all bears witness of the great care given to the disposal of sewage and the efforts to carry it away from the fort as far as possible. An interesting parallel is Ribchester where a channel passed under the southwest corner of the fort and crossed the berm and ditch before heading for a large stone-lined pit (Hopkinson 1928: 13 and plan; for aqueducts on Hadrian’s Wall: Bidwell 2018: 53-6). The phenomenon of settling tanks as part of sewage works could make sense of the reputedly Roman ‘well’ shown on

the Ordnance Survey sheet of 1859 in the northeast corner of Auchendavy close to the lip of the Ditch (Keppie and Walker 1985: 31). In the corresponding fort quadrant, the 2006 geophysical survey shows a linear negative anomaly that could represent the south wall of a sanitary suite placed along the Rampart, like at Bar Hill (Jones and Leslie 2015: fig. 22.2; Richard Jones, pers. comm.).

What is clear in most cases is that the waterworks and sewage arrangements were an integral part of the construction of the fort. This care for good sanitation is apparent from the very start of the Antonine Wall project. Balmuildy had its sanitary suite prepared for by a channel that passed through the base of its stone north wall (Miller 1922: 41). At Castlecary, likewise, an impressive system of drains was planned and at least partly built before the north wall of the fort (Buchanan 1903: 320-25 with pl.

IV and fig. 26). The internal reorganisation of Bearsden while the fort was under construction shows that the sanitary suite was one of the first buildings taken in hand (Breeze 2016: 323, 345-46), likely involving specialist construction teams.

Croy Hill revisited

In the winter of 1931-32, Macdonald had small-scale excavation work carried out at Croy Hill to elucidate points about the fort he had discovered, or rather confirmed, there in 1920. Sir George was looking for corner towers, but what he found instead, just inside the northeast corner of the fort, effectively undermining it, was a rectangular pit lined with ‘first-rate’ masonry (Figure 11.11). It measured 3.3 m (north to south) by 1.8 m at the top and 2.1 m by 1.2 m at the bottom, 2.1 m below, where a circular hole had been cut into the bedrock for another 0.9 m. The east side of the structure appeared to have been demolished (rather than simply collapsed, as most of the corresponding masonry was missing).

On the west side of the pit, a flight of steps descended almost to the base of the structure, while a pivot stone indicated the door of a former cover building. An appurtenant culvert, clearly of one build with the stone lining of the pit, passed under the stone base of the Antonine Wall at a depth of 1.25-1.4 m.

Strangely, the channel, which had been constructed with great labour, part rock-cut, part paved, lined and capped with stones, did not cross the berm in the shortest possible way, but at an angle of about 45° (Macdonald 1932: 251-57 with figs 7-12).

To Macdonald it was clear that the pit had been constructed prior to the fort, likely in connection with the bathhouse that was situated just outside the east wall. The reverse order is unlikely. The east side of the construction pit for the ‘well’ would have dangerously undermined the fort wall. Moreover, Macdonald reported that the ground under the fort rampart had been dug and ‘made up’ afterwards.

‘In a length of little more than 4 feet there was a central depression a foot and a half deep’. Immediately east of the fort wall, the ground was found to have been excavated to a depth of at least 3.6 m below the modern surface. ‘The cavity contained much black and red matter, resembling the waste products of a furnace’, tentatively interpreted as ‘refuse from the hypocausts’ of the adjacent bathhouse (Macdonald 1932: 251 with fig. 12 section B-B). Interestingly, the ‘stone-lined pit’ also contained various layers of

‘black burnt’ and ‘red burnt matter’ as well as ‘a 6-inch layer of coal ashes’ (Macdonald 1932: 252). The strong impression gained from Macdonald’s report is that the eastern fort wall had been constructed over an earlier structural complex or sequence which comprised not just the pit with its cover building but also a deep channel or cavity immediately east of it, the fill of which had slumped under the load of the later fort rampart.

Figure 11.11. Plans and sections of stone-lined pit beneath the north-east angle-tower of fort at Croy Hill (after Macdonald 1932: fig. 12).

The ‘stone-lined pit’ may either be a combined cistern/sump accessing a natural spring or a settling tank/maintenance pit as part of a sewage system connected to a latrine. The OS 25 inch map surveyed in 1896 shows a ‘well’ southeast of the fort, while the ponds in front of it must have been fed from a local source (Macdonald 1934: 266-67). However, if so much effort and investment had been done to secure a water supply, why was this demolished when the fort was constructed, possibly within a year or two, as the Gillam hypothesis would imply? They could have saved this vital piece of infrastructure by moving the fort rampart just 1 m to the east – quite apart from the structural problems of constructing a fort rampart over an active spring. Strangely, also, the depth at which the culvert had been built would have largely emptied the reservoir – rather than an ‘overflow’ this element looks like the end-piece of a main drain. The narrow cover building implied by the pivot-stone, too, would seem more readily explicable in a context of sanitary service and maintenance than ‘public’ distribution of water.

The quality of the masonry, and the use of stone generally (especially in an Antonine Wall context), would normally point to one of a fort’s main buildings, a bath-latrine suite being the obvious candidate.

Whether it held water or sewage, the stone-lined pit with its service facilities would be well-placed in relation to the adjacent bathhouse, with the cover-building leaning onto a larger structural complex to the east. If a well, the destruction, or at least separation, of this element by the fort rampart may have led to the search for an alternative immediately east of it, where Macdonald found the ground to have been dug to a depth of at least 3.6 m. Interestingly, both cavities were found to contain waste products that one would normally associate with the adjacent bathhouse. Whatever the exact sequence, the crucial point is that the stone-lined pit with its laboriously constructed conduit predates the eastern fort wall and was apparently built in conjunction with (or in anticipation of) the local section of the Antonine Wall Rampart.

The secondary construction of the known fort is in no doubt. Apart from the stratigraphic evidence at the north corners (Macdonald 1932: 247), we have the enclosure with its associated annexe that preceded the fort. It is of proven Antonine date and appears to have existed for some time, to judge the accumulation of silt in its ditches (Jones, this volume). It has been suggested that this camp may have serviced the surveying of the Antonine Wall, along with the early ‘enclosure’ on Bar Hill (Jones 2011: 330). Interestingly, a gully coming from the enclosure’s southeast corner merges with the ditch for a Roman road track that appears to have by-passed the designated fort site. This may indicate that the enclosure on Croy Hill remained in operation for some time after the fort site had been planned.

The fort on Croy Hill fell in with the two-mile spacing guideline, it enjoyed extensive views to the north and east, it lay close to a penetrating valley, and it was intervisible with its two neighbours.

Although inevitable as a link in the chain of installations, the fort as documented by Macdonald is clearly not in its original position. We have just seen that the east wall overrode structures of a nature and sophistication that one would normally associate with a fort. The north gate of the fort was ‘not in the middle, as one might have expected, but decidedly nearer the west’ (Macdonald 1932: 247). This eccentricity was probably caused by the kink in the fort’s north face. This is without parallel on the Antonine Wall, but reminiscent of milecastle 40 on Hadrian’s Wall which may have been moved from its original position like milecastle 39 (Symonds and Breeze 2016: 3-4).

There is, of course, a possible pointer to an alternative fort location on Croy Hill and that is the causeway over the Ditch, some 70 m east of the gate of the known fort. Macdonald praised the visual affordance

of this ‘bridge’. ‘Standing on the “flattish top” one cannot but feel that it would have made an ideal signalling station: the view is most extensive in almost every direction’ (1925: 290). It has been noted that the Ditch terminals on both sides of the causeway do not align, perhaps marking ‘the change-over between two construction parties’ (Hanson and Maxwell 1986: 108). Interestingly, the Ditch also changes in width at the north gate of Castlecary and across the front of Balmuildy (Graafstal et al. 2015:

62). So this may be another instance of a purported ‘secondary’ site mirroring phenomena seen at

‘primary’ forts (cf. Table 11.1). As Hanson and Maxwell observed, the causeway at Croy Hill ‘suggests foreknowledge of the existence of the fort on the part of the Ditch-diggers’ (1986: 108). Macdonald also concluded that ‘its existence must somehow or other be connected with the proximity of the castellum’

(1934: 262-63).

An abortive fort?

This invites a simple test: what happens if a hypothetical fort about the size of Croy Hill is aligned with the causeway? The result is a surprising fit of various bits of evidence (Figure 11.12). The baths and the stone-lined pit with its cover building would admirably go together as the east and west ends, respectively, of a sanitary suite of the familiar row-type. Like at Westerwood and Bar Hill, Croy’s direct neighbours, this suite would land in the notional fort’s northwest corner. The curious course of the conduit, crossing the Berm at a 45° angle, would make perfect sense as part of the sanitary suite’s waterworks or sewage system, typically turning away from the northwest corner of the putative fort to carry its contents as far off as possible, like at Falkirk and Ribchester. Finally, what suddenly becomes apparent west of the notional fort corner is a potential wing-wall of similar length to Mumrills, Cadder and Castlehill. The way all these elements (causeway, sanitary suite, conduit, wing-wall) add up to a perfectly acceptable Antonine Wall fort-front is almost too good be coincidental.

In this mental exercise, the implication of the structural sequence at the ‘stone-lined pit’ would be that, before plans changed, a start had been made with a few essentials for the sanitary suite. At the very least, the part of the channel that was to pass under the Rampart had been built. Like Bearsden, it is conceivable that the bathhouse had been given priority, perhaps because it would take more time and required specialist skills. It even seems possible that construction of the north face of the fort, wing-walls included, had started. At Cadder, it looks as though the north side had taken a head-start, with the porta praetoria sufficiently progressed to leave it where it was when the change of the fort’s orientation occurred. Interestingly, Macdonald noted that south of the causeway on Croy Hill, ‘there were unmistakable signs of disturbance and occupation – intrusive clay, black matter, two sherds of pottery, and some appearance of post-holes’ (1932: 245).

If this makes any sense at all, there must have been a change of plan very early in the process. Perhaps it was realised that the terrain was too problematic: the west half of a fort centered on the ‘bridge’ would have ended up on an awkward slope. It is true that the complexities of British frontier design, with the choice of fort sites limited by the course of the barrier wall and subject to various other norms (spacing,

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