Gretna, Hm Factory, Eastriggs Explosives Factory, Acids Section, Gas Producers, Main Flue

Canmore ID: 375018

NY26SW 38.30

NY 24998 64931 (centred)

This earthwork, which is overgrown with grass, nettles and trees, zigzags through the dense deciduous scrub for a distance of about 300m (NY 24895 64984 – NY 25177 64886). It runs from the Nitre Dryer (NY26SW 38.13) via the gap separating the Retort Houses (NY26SW 38.11, NY26SW 38.12) in the WNW to the remains of the Gaillard Towers (NY26SW 38.26) in the ESE. The earthwork measures about 6m in width and 0.4m in height close to the Retort Houses, becoming much more pronounced as it approaches the Gas Producer plant (NY26SW 38.29), in rising to a height of 0.8m. Its flanks in this section are marked by a series of large rectangular concrete blocks of triangular cross-section, which are carefully spaced at equal intervals along its length. Where the earthwork is broken open at the ESE end of this section it can be seen to enclose three brick-built flues of rectangular cross-section each capped by a rounded arch. Little trace of the earthwork can be clearly observed immediately S of the Gas Producers plant. However, it does become visible again as it runs on to the Gaillard Towers, although it is reduced to only 0.4m in height in this section.

The course of the earthwork is shown on the plan of, and in text referring to, the works the works (MMW 1919, plan, 109-11, diagram) 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 is identified in the text as the Main Flue. This flue supplied coal gas to the Nitric Acid Still House (NY26SW 38.31) and the Retort Houses in one direction and to the Gaillard Towers in the other. Another branch supplied coal gas to the Denitration Plant (NY26SW 38.28) to the SSW and although this was not observed, it is clearly shown on an undated map (SUPP 10-39) held by the National Archives at Kew. Ground-based, contemporary official photographs (MUN 5-297 pt2, 225, 251A, 284; MUN 5-297 pt3, 389) also held at Kew, taken during the construction of the section adjacent to the Gas Producers, shows the character of the flues in that sector.

The earthwork fell into lots 507 and 508, which were offered for sale by auction on 22-5 July 1924 (HM Treasury 1924, 101), when the lots were divided between J. M. Temple, Blackhills, Eastriggs and Messrs James Jackson & Co Ltd, St Vincent Street, Glasgow (Carlisle City Ar-chives, DX 2040/3). The brickwork of the flues immediately south of the Gas Producers plant and the steel plate ‘burning out’ chimney was removed; but otherwise, the foundations of the flues leading WNW and ESE 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), 10 May 2022.