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

Canmore ID: 374398

NY26SW 38.11

NY 24903 65038

This moss- and grass-grown concrete platform is situated in dense deciduous scrub woodland about 15m NNE of the Retort House South (NY26SW 38.12). It was once outlined by two rows of concrete footings for steel stanchions on the WNW and ESE. However, on the SSW there is only a single row of footings. The building is rectangular on plan and measures about 93m from NNE to SSW by 20m transversely. The whole structure has been heavily dumped over and the ESE side of the bund surrounding Explosives Magazine R10 (NY26NW 46.12) overlies much of its WNW side. It is also slighted by the Narrow-Gauge Railway line (NY26NW 46.27) running between Explosives Magazines R10 and R11 (NY26NW 46.12) and it is also bisected by a deep drain (NY26NW 46.33) S of the bund of R10. There are the remains of an outshot on the ESE side.

This 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). Like its counterpart to the SSW (NY26SW 38.12), this is where the nitre (sodium nitrate) and sulphuric acid were heated in twenty-four re-torts using fuel from the Gas Producers Plant (NY26SW 38.29) in the manufacture of nitric acid. The strong nitric acid was then transferred to tanks in the outshot from whence it was conveyed to the northern Preliminary Mixing Houses (NY26SW 38.37). Descriptions 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, 248; MUN 5-297 pt2, 248, 284, 251A; MUN 5 -297 pt3, 373, 439, 440, 448, 450, 475, 524, 543, 544, 545; MUN 5-297 pt5, 684, 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 and there was a chimney midway down the same side, now overlain by Explosives Magazine R11. The North and South (NY26SW 38.11) Retort Houses were connected by a cabin at a high level. This also provided access on the WNW just below roof level to a walkway running the full length of this Retort Houses. In addition, another walkway from the cabin ran to a high level in the Cummer Nitre Dryer (NY26SW 38.13).

This structure fell into lot 507, which was offered for sale by auction on 22-5 July 1924 (HM Treasury 1924, 101, item 1). The catalogue adds that the building measured 7.5m in height. 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 read-ily visible on an aerial photograph (M124/13 04117) flown on 19 August 1940.

Visited by HES Heritage Recording (MMD and ATW), 11 May 2022.