Gretna, Hm Factory, Eastriggs Explosives Factory, Acids Section, Retort House South

Canmore ID: 374399

NY26SW 38.12

NY 24877 64936

This moss- and grass-grown concrete platform is situated in dense deciduous scrub woodland about 48m E of the Mannheim Oleum Plant (NY26SW 38.02). It is outlined by a low narrow wall and two rows of concrete footings for steel stanchions spaced 2.5m apart on the WNW and ESE. However, on the SSW there is only a single row of concrete footings. The building, of which these form part, is rectangular on plan and measures about 93m from NNE to SSW by 20m transversely and its concrete floor stands to a height of 0.25m. The whole structure has been heavily dumped over and the floor itself is only clearly visible at the SE corner of the building. However, there is a substantial outshot midway along the ESE side which measures 24m in length by 5.5m in width. In addition, there is a brick-built flue on the WNW measuring 2m in width and up to 1m in height. This is broken open on the ESE revealing the internal brick arch. The flue terminates on the WNW in a ruined chimney stack base (NY24853 64938). There is a ring of vertical iron bars measuring 3m in diameter by which the tall mild steel chimney was attached to the masonry. Three large concrete anchoring blocks, which are situated to the NW, SW and SE, were introduced to help stablilise the chimney. These blocks measure 2m by 1.5m and 0.75m in height. The sloping facets directed towards the chimney retain the remains of a single, centrally positioned, metal, threaded bolt (see NY 26NW 46.19 for comparable blocks).

The building is identified as a Retort House on the plan of, and in text referring to, the works (MMW 1919, plan, 61-71, diagrams) given in the report by the Ministry of Munitions of War outlining the processes involved in the manufacture of the cordite propellant during the First World War at H.M. Factory, Gretna (Site 3). It was where the nitre (sodium nitrate) and sulphuric acid were heated in twenty-four retorts using fuel from the Gas Producers Plant (NY26SW 38.29) to manufacture nitric acid. The strong nitric acid was then transferred to tanks in the out-shot from whence it was conveyed to the southern Preliminary Mixing House (NY26SW 38.37). De-scriptions of blueprints (SUPP 10-16, 3032; SUPP 10-19, 3624, 3630; SUPP 10-120, 3659; SUPP 10-22, 4198, 4266, 4279) and blueprints (SUPP 10-27, 3802, 3659; SUPP 10-31, 4279) held in the National Archives at Kew, together with ground-based contemporary official photographs (MUN 5-239, 197; MUN 5-297 pt1, 125, 144, 173, 174, 182, 183, 205, 248; MUN 5-297, pt2, 242, 248, 284, 251A ; MUN 5 -297 pt3, 372, 439, 450, 472, 475; MUN 5-297 pt5, 710E) taken during and after construction also held at Kew, show that the building was a single storey, single bay, steel framed structure clad with corrugated iron sheets. It had a ridge roofed with skylights and a vent running its full length. The brick-built furnaces within the interior were on the WNW side of the building, while the North Re-tort House (NY26SW 38.11 and South Retort House described here were connected by a cabin at a high level. A walkway from this cabin also provided access to the Nitre Dryer (NY26SW 38.13) on the WNW just below roof level and another walkway ran the full length of both Retort Houses.

This structure fell into lot 507, which was offered for sale by auction on 22-5 July 1924 (HM Treasury 1924, 101). The lot was bought by Messrs James Jackson & Co Ltd, St Vincent Street, Glasgow (Carlisle City Archives, DX 2040/3). After its removal from the site, only the foundations were left in place and these are readily visible on an aerial photograph (M124/13 04117) flown on 19 August 1940.

Visited by HES Heritage Recording (MMD and ATW), 26 January 2022.