For important guidance on the use of this record, please click here.

If you have any comments or new information about this record, please email us.

Summary

A subterranean engine room with associated tunnel, ventilation holes and access ramp.

Protected Status

• Scheduled Monument 15434: POST-MEDIEVAL BREASTWORK, CURTAIN WALL AND ASSOCIATED DEFENSIVE STRUCTURES ON THE PERIPHERY OF THE GARRISON, ST MARY'S

Other References/Statuses

• Heritage at Risk (National)
• National Mapping Programme (Morph No.): 60.2.10
• National Monuments Record: SV 81 SE 515
• National Record of the Historic Environment to Historic Environment Records data transfer
• National Record of the Historic Environment: 1445714
• Primary Record No. (1985-2009): 7908.13

Monument Type(s):

• ENGINE HOUSE (19th Century - 1801 AD to 1900 AD)
• GENERATOR HOUSE (19th Century - 1801 AD to 1900 AD)

Full description

A largely subterranean concrete structure, rectangular in plan, was built in the 1890s as an engine room in the C18 Colonel George Boscawen's battery (7906.29). The battery is a Scheduled site. The rectangular building, aligned NW-SE with the face of the C18 battery, is recorded on the 1907 OS 1:2500 map (b1). Steps from the north west corner lead down to its north east side. The 1978 OS fieldworker noted a probable magazine incorporated in the angular battery (h1). A function as a radar or fire control point was suggested in 1984 (h2). In 1990, a tunnel draining the subterranean works was recorded after stones partly closed its beach-boulder fill (h4, b2). Some 3.5m of tunnel was exposed, running NNE from its opening at the low cliff at SV 8955 1014 towards the southern corner of the installation. It is cut into the rab with fairly straight sides and roof, with traces of retaining timbers, and measured approximately 1.5m wide and 1.5m high. A ceramic pipe was visible beneath boulders along the south east side of the tunnel. Features of the structure, identified as an engine room for an oil-fired generator, itself were also noted in 1990; blocked ventilation holes and ramp giving access to the flat roof and modified battery walls (h5). The monument is included in the Schedule. The site is visible on aerial photographs (p1) and was plotted as part of the NMP.

The site was described in 2005 by English Heritage (3; see also 4): It was constructed to house two petrol driven generators that provided power for the two Defence Electric Lights (DELs) - one at Steval to the north and the second at Woolpack to the south. It also provided electrical power for the two Searchlight Director Stations that are situated on the hillside above the DELs. The windows and doors of the sunken building have been blocked up; the square ventilation pillars survive on the flat rooftop. The moat is clear and the access steps are in good order. The building is well maintained and enclosed by a chainlink fence that was replaced in 2005. The tunnel that conveyed surplus cooling water from the building is slowly being eroded by cliff erosion. The DELs and the Director Stations provided the illumination and range data for the guns mounted on the hilltop behind them. Whether electrical power was also provided for the guns by these generators is not known but it seems unlikely. The gun batteries were built in 1900 so it seems probable that the generators, lights and observation stations were constructed at more or less the same time.

--------------------------------
Site history:
1: 1978. NJA/OS
2: 1984. UNKNOWN/MSC-ICS
3: 1988. WATERS, A/CAU
4: 1990. HERRING, P AND PARKES, C/CAU
5: 1990. JOHNSON, N/CAU
--------------------------------

<1> Ordnance Survey, 1900s, 2nd Edition 1:2500 Map (Cartographic materials). SCO4050.

CAU, 1987, CAU/F14/106,149 (Photographic Record). SCO17007.

<2> RATCLIFFE, J & PARKES, C, 1990, ARCHAEOLOGICAL FIELDWORK IN THE ISLES OF SCILLY, MARCH 1990, 23 (Unedited Source). SCO8940.

<3> Field Investigator's Comments, HE/Fletcher, M. 2005. (Survey). SCO29739.

<4> Brodie, A, 2011, The Garrison, St Mary's Isles of Scilly: The Defences of the Garrison 1500-1945 - survey report, 59, fig. 38 (Bibliographic reference). SCO24047.

Sources / Further Reading

Associated Finds: none recorded

Associated Events

• ECO3128 - Garrison Walls, Isles of Scilly, conservation plan
• ECO6309 - The Garrison, St. Mary's: Survey
• ECO3819 - Isles of Scilly Military Defences, 1540-1951 (Ref: RDRS 56-2011)

Related records

Search results generated by the HBSMR Gateway from exeGesIS SDM Ltd.