Gretna, Hm Factory, Eastriggs Explosives Factory, Nitroglycerine Hill No. 2

Canmore ID: 373568

NY26SE 16.02

Centred NY 26280 64649

What remains of the buildings that once formed part of this Nitroglycerine Hill are situated on a ridge, the gradient of which eases gently as the topography levels off in boggy ground to the NNW. They comprise the greatly reduced remains of the blast mound of a Final Wash House (NY 26400 64561), the blast mounds of six Paste Mixing Houses (NY 26208 64583, NY 26291 64610, NY 26375 64636, NY 26186 64660, NY 26268 64686, NY 26347 64712), the blast mound of a Dry Guncotton Store (NY 26241 64762), the blast mounds of two Paste Magazines (NY 26264 64916, NY 26393 64959) and an Off Loading Platform (NY 26316 64974). In addition, the ancillary infrastructure includes, amongst other elements, the remains of a narrow-gauge and a standard-gauge railway network (NY26NW 46.23, NY26NW 46.24). As the processes involved in the production of Nitroglycerine relied largely upon gravity to enable the movement of the constituent fluids in a continuous direction, all these buildings are carefully arranged in an ordered sequence and so take account of the slope of the ground. In addition, they are deliberately spaced – the blast mounds of the Final Wash Houses and the Paste Mixing Houses being set 48m apart, the Dry Guncotton Store 43m from the latter, while the Paste Magazines are distanced 100m from the Dry Guncotton Store and also from one another.

The demolished grass-grown remains of the Final Wash House blast mound on the ENE measures roughly 35m square overall. Although it is poorly outlined, the position of its former entrance on the W side of the earthwork can be determined by the approach of the narrow-gauge railway embankment. By contrast, the grass-and gorse-grown blast mounds of the six Paste Mixing Houses to the NNW are rectangular on plan with rounded corners; and each measures about 36m from WSW to ENE by 30m transversely overall within earth and stone banks 11m in thickness and up to 3.5m in height. The two most easterly blast mounds have entrance gaps in the NNW side offset to the ENE, while their four neighbours have entrance gaps in the same side offset to the WSW. Each is approached by the remains of a narrow-gauge railway embankment. The grass-grown blast mound of the Dry Guncotton Magazine to their NNW measures roughly 42m square overall within earth and stone banks 15m in thickness and up to 3.5m in height. There is an entrance gap on the ENE off centred to the SSE and this is also serviced by the narrow-gauge railway network. The grass- and gorse-grown blast mounds of the two Paste Magazines are situated between this Hill and Hill 3 (NY26SE 16.03). They are rectangular on plan and measure 42m NNW to SSE by 35m transversely overall within earth and stone banks 12m in thickness and up to 3.5m in height. The more westerly has an entrance gap on the ENE offset to the NNW, while its counterpart to the E has an entrance gap on the WSW offset to the SSE. They are also serviced by the narrow-gauge railway network. The embankments leaving these gaps run to what remains of the Off-loading Platform situated about 16m to their NNW. This grass-grown earthwork, which is situated immediately SSE of the road, is rectangular on plan and measures 34m from WSW to ENE by 8m transversely.

The structures associated with this Nitroglycerine Hill are referred to in the report (MMW 1919, 145-163, plans in text) outlining the processes involved in the manufacture of the cordite propellant at H.M. Factory, Gretna (Site 3), which was established by the Ministry of Munitions during the First World War. This section of the factory comprised a complete plant for the manufacture of Nitroglycerine. Apart from the blast mounds described above, other key buildings were also associated with this plant. These included a Chemists Hut (NY 26311 64373), a Glycerine Dump (NY 26333 64380), a Soda Solution Dump House (NY 26344 64387), a Charge House (NY 26344 64411), Acid Storage Tanks (NY 26353 64390), an Acid Dump House (NY 26351 64397), a Brine Store (NY 26381 64402), a Nitrator Separator House (NY 26371 64432), Air Storage Tanks (NY 26402 64445), two additional Final Wash Houses (NY 26254 64479, NY 26335 64510), a Wash Water Settling House (NY 26740 64607 - shared with Nitroglycerine Hill 3, NY26SE 16.1), a Pond (NY 26445 64668), a Waste Collecting House (NY 26163 64535), a Rest Room (NY 26425 64770) and more minor structures such as latrines and shelters. In addition, an undated plan (SUPP 10-39), a series of descriptions of blueprints (SUPP 10-16 3075A, 3076, 3076A, 3077, 3090A; SUPP 10-17 3202; SUPP 10-18 3376; SUPP 10-19 3562; SUPP 10-20 3737; SUPP 10-35 unnumbered blueprint), some actual blueprints (SUPP 10-24 3075, 3076, 3090, 3090A, 3097, 3196, number indistinct 3202, 3208, 3211A; SUPP 10-25 3288, 3376; SUPP 10-26 3507, 3562; SUPP 10-27 3737, 3798A; SUPP 10-28 3910; SUPP 10-31 4365), together with ground-based, contemporary official photograph taken during and after construction (MUN 5-239, 201, 202, 239; MUN 5-239; MUN 5-297 pt1, 142, 166, 186, 187, 233, 233A; MUN 5-297 pt2 158A, 158B, 158C, 158D, 159, 160; MUN 5-297 pt3, 352A, 353A; MUN 297 pt5, 713), held at the National Archives at Kew, illustrate the character of the buildings on this Hill. These sources show that the chemicals were brought to the top of the Hill where there was a cluster of buildings around the Nitrator Separator House - the acids being piped in on a high trestle, while the glycerine and the soda ash were brought in by standard gauge rail.

The Glycerine Dump was a brick-built, single storey structure with a Belfast roof. It was rectangular on plan and measured 12m from WSW to ENE by 6m transversely and 2.5m in height. A timber veranda extended from the SSE and this faced onto the standard-gauge railway line. Beneath the sloping roof of the timber veranda was a loading platform onto which the drums from the Glycerine Distillery (NY26NW 92) were stacked. The elevation of the building to the rear of the veranda contained two broad doorways at either end and between these there were four tall windows. There were also six windows in the NNW elevation and three in each of the gables ends. The glycerine was pumped from this building to the Soda Solution Dump House, which was a three-storeyed timber building with a Belfast roof. It was rectangular on plan and measured 9.5m from NNW to SSE by 5.5m transversely and 5m in height. A veranda extended from the SSE which also faced onto the standard-gauge railway line. Beneath its sloping roof was another loading platform onto which bags of soda ash were stacked. Both the WSW and ENE elevations had tall double windows below the eaves lighting the upper storey, with three neatly spaced windows below them and one window on the ground floor at the N corner. There was at least one window in the NNW elevation. From this building, the soda solution was pumped to the Charge House which was divided into two parts: the Soda Charge House and the Acid Charge House. The Soda Charge House was where the soda ash was mixed with water to form a cleaning solution. This was then sent to the three Final Wash Houses and to the Nitrator Separator House where it was employed to remove excess acids from the nitroglycerine. The Acid Charge House was where the blend of nitric and sulphuric acid was received from the two Acid Storage Tanks, which were situated immediately SSE of the Acid Dump House. These Tanks were supported by dwarf walls and covered over with a light roof. The Charge House, which rested on a tall wooden framework, was rectangular on plan and measured about 8m from ENE to WSW by 7m transversely. It was a timber-built, single storey building with a Belfast roof covered in rubberoid. There were five equally spaced windows in the WSW and ENE elevations, while there was a louvre in the S gable, below which there were six windows. The fenestration in the N gable was similar, but there were two doorways below the windows which led out onto a walkway from the Acid and Soda sections of the building. This walkway linked to a bridge that connected the Charge House with the Nitrator Separator House. The pipework carrying the mixed acids, the spent acid, the soda solution and the glycerine ran beside this bridge and entered the building at a high level, while a flight of steps led down from the bridge and provided access to the entrance of the Nitrator Separator’s House.

The Brine Storage Tank was situated 15m SSE of the Nitrator Separator House and the tank, itself, was supported on a brick tower (see NY26SE 16.01). The brine (or salt water) was sent to the Nitrator Separator House where it was used to cool the Nitrator Separator vessels. The latter building was located within a blast mound that was rectangular on plan and measured 28m from NNW to SSE by 26m transversely within an earth and timber revetted bank 6m in thickness and up to 6m in height. This blast mound was broken by three tunnels, one for a narrow-gauge railway line which ran along the ENE side of the building, a second on the same side close to the N corner, which served as an escape tunnel and a third in the centre of the NNW side above the Final Wash Houses. The Nitrator Separator House was rectangular on plan and measured about 13m from NNW to SSE by 9m transversely within timber walls rising 7m in height. It was divided into two main parts: a tall section on the NNW and an outshot to the SSE. The NNW part contained three levels comprising an upper section holding the glycerine tanks, a middle section that was the main operating area and a lower section for the equipment that produced the nitroglycerine and sent it through the tunnel to the Final Wash Houses. This section extended into the outshot, below which there was a ‘Drowning Tank’ and additional equipment that could be employed in the case of an emergency if the temperature reached a dangerous level during the nitrating process. Windows in the elevations provided ample light at each level and to the SSE of the outshot there were three Fume Towers. Outside the Nitrator House and about 16m ENE of the bund, there were four Air Storage Tanks. These were supported on low dwarf walls and occupied an area measuring 10m square. The compressed air they contained was not only employed in the process of nitration, but also the movement of the chemicals around the plant.

The three Final Wash Houses were where the remnants of the nitrating acid were removed from the nitroglycerine to diminish the possibility of explosion; but it was also where the bags of nitro-cotton were saturated with the nitroglycerine to form ‘Paste’ prior to being dispatched to the Paste Mixing Houses by narrow-gauge rail. The three that formed part of Hill No.2 were situated below the Nitrator Separator plant. The blast mounds within which they were located were rectangular on plan and measured 25m from ENE to WSW by 21m transversely within an earth and timber revetted bank 5m in thickness and up to at least 4m in height. This bund was broken on the SSE by the wooden gutter running in a trench from the Nitrator Separator House that brought the nitroglycerine into the Wash House at a high level. It was also broken on the NNW by a timber-lined tunnel through which the narrow-gauge railway trolleys were brought into the outshot on one side of the building. These buildings were also rectangular on plan and measured about 11m from ENE to WSW by 8m transversely. They were timber-built structures containing three levels with Belfast roofs covered with rubberoid. Centrally placed louvres were placed below the gable eaves and two windows below that on the SSE - this arrangement may have been replicated on the NNW. By contrast, there were four spaced windows in one of the longer elevations, while there was only an escape door in the opposite elevation above and behind the outshot. The latter had a sloping roof and was also lit by at least two openings.

The waste water from the Final Wash Houses was conducted to either one of two Wash Water Settling Houses by means of a raised wooden covered gutter where the very last remnants of nitroglycerine were filtered. Hill 2 shared the more westerly Wash Water Settling House and Pond with Hill No.1 (NY26SE 16.01), while it shared the more easterly with Hill 3 (NY26SE 16.03). Neither had blast mounds. These buildings were timber-built, single storey structures with Belfast roofs covered with rubberoid. There were louvres in the gable ends under the eaves, below which there were five windows and a door positioned close to one corner. Four equally spaced windows were in one of the longer elevations and this may have been duplicated in the other. The wastewater residue was drained to the Ponds where Dynamite was used to disperse any remaining traces of nitroglycerine.

Hand-pushed trolleys running on the narrow-gauge railway line brought the bags of ‘Paste’ from the three Final Wash Houses (see photograph: National Record of Scotland, GD1-1011-76 (592)) down to the six Paste Mixing Houses. Here the ‘Paste’ was hand-mixed and sieved to render the mixture into Cordite Paste before being put into bags again and then being transported to the Paste Magazines. Each blast mound was broken by a tunnel off-set from the centre through which the narrow-gauge railway trolleys were brought into an outshot on one side of the building. These buildings were rectangular on plan and measured 12m from NNW to SSE by 7.5m transversely and 2.7m in height. They were single storey, timber-built structures with Belfast roofs covered with rubberoid. One gable had a louvre centred under the eaves and two tall windows, while there were also two long windows in the SSE elevation.

The Dry Guncotton Magazine was where the dried nitro-cotton from the Drying Houses (NY26NE 146) was stored prior to being sent up the hill to the three Final Wash Houses where it was combined with the nitroglycerine. This building was rectangular on plan and measured 9m from ENE to WSW by 6m transversely within timber walls 0.1m in thickness and about 3m in height. It was a single storey structure with a Belfast roof covered with rubberoid. One gable had a louvre under the eaves below which there was single window, while there were two wide windows in the longer NNW and SSE elevations. An outshot on the SSE of the building contained two long windows and double doors facing ENE which led out to the brick-lined tunnel running through the blast mound.

The two Paste Magazines were where the Cordite Paste that had been mixed by hand in the Paste Mixing Houses was stored before being moved to the Loading Platform where it was transferred to the cordite ranges at Mossband. This part of the factory was situated 7km to the NE and the Cordite Paste was transported there in standard gauge railway wagons pulled by a fireless locomotive. The Paste Houses were rectangular on plan and measured about 13.5m from NNW to SSE by 10m transversely within timber walls. They had a Belfast roof which was covered with rubberoid. There was an outshot attached on the NNW of the more westerly building and on the SSE of the more easterly building. The Loading Platform from which the Cordite Paste departed for Mossband was situated to their NNW. It was rectangular on plan and measured 16m from ENE to WSW by 6.5m transversely and varied between 4m-5m in height. This building was divided into two parts - its Belfast roof straddled the narrow-gauge railway line to the SSE and the standard gauge railway line to the NNW. The narrow-gauge section was timber built with three large windows below the eaves, while the standard gauge section was metal-framed and largely unclad. The brick-built loading platform, which measured 1.5m in width, was situated between the two railway lines. However, the narrow-gauge railway was at a higher level. Hill No.2 shared its six Paste Mixing Houses, Dry Guncotton Store, Paste Magazines and Off-loading Platform with Hill No.1 (NY26SE 16.01).

This Nitroglycerine Hill fell into lot 491, which was offered for sale by auction on 22-5 July 1924 (HM Treasury 1924, 89; Carlisle City Archives, DX 170/38), when it was purchased by Greenwood & Another of Broomhills, Eastriggs (Carlisle City Archives, DX 2040/3). After all these buildings had been removed from the Hill, only the foundations and the blast mounds were left in place and these are readily visible on an aerial photograph (M124/13 04127) flown on 19 August 1940. However, Nissen Huts (NY26SE 16.06) had already been introduced into the blast mounds of the three Final Wash Houses, the six Paste Mixing Houses, the Dry Guncotton Store and the two Paste Magazines. Another aerial photograph (CAM/031 06210) flown on 13 October 1942 shows that the most westerly and easterly blast mounds of the three Final Wash Houses had been damaged, while that of the Nitrator Separator House had been destroyed by the introduction of explosives magazine R58 (NY26NW 46.12). By 1963 the most easterly blast mound has been reduced to its present state (USN/219/206 0008-0009, flown on 26 July 1963) and little of the three survived by 1975 (39/RAF/4701 P0025, flown 6 May 1975).

Visited by HES Heritage Recording (MMD and ATW), 7 September 2022.