Concrete Ring

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The original exposed Concrete Ring at Blencathra
The replacement Concrete Ring at Blencathra
A buried Concrete Ring
Example of inscription

'Concrete Ring' is a trig bagger's term denoting a feature of some buried blocks seen in Lakes/Northern Pennines and elsewhere. Typically, the ring is approx 15" internal and 21" external diameter. It usually bears the inscription "Ordnance Survey Trigonometrical Station" although this may be eroded or absent. The ring is placed loosely above the block. The block itself typically has a central, slightly conical bolt of approx 3" diameter. Occasionally, a ring may be used to mark a buried bolt set into bedrock, for example, Brownsey Moor. Infrequently, the trig mark may be a rod instead of a bolt, for example, Stonesdale Moor.

Initially, when very few examples of concrete rings had been rediscovered, they were considered by some baggers to be a decorative feature, lacking a functional use. Subsequently, it was understood that they were identical to the OS term Emplacement Ring (or Detector Ring) as described in Section 7.032 and Fig 7.7 of [1] as follows:

When used as a secondary station a phosphor-bronze ring was buried with the block so as to enable it to be detected by mine detectors if the locating description should prove insufficient. With the lower order stations these rings were replaced by scrap iron incorporated in the block itself.

Some, but not all, concrete rings have an embedded metal ring (originally phosphor-bronze, subsequently iron). With the use of a metal detector the emplacement ring can assist in locating a trig mark, but is not in itself a mark. It was discovered quite late on that the manufacturer decided to leave out the metal ring to save money. Hence many rings are just concrete [2].

The OS online records do not identify which blocks have emplacement rings, hence it is not known how many exist. The paper-based OS Office files (held at The National Archives) and Field files are understood to record this information although not systematically [3].

Until 2014, 10 Concrete Rings had been located, all in Northern England. However, they have subsequently been located more widely with 26 having been identified by late 2019, 51 by the end of 2022 and 52 by January 2023.

A photo album of concrete rings is available from T:UK, where a listing can also be accessed.

In 2018 the Concrete Ring on the buried block at Saddleback, located at the summit of Blencathra, was reported missing, presumed stolen. A replica was installed in early 2019 and has since suffered minor damage. The ring for Moss Farm was also lost, a few months after its rediscovery.

T:UK Station name Order Computed Block Rediscovered
TP19379 Abercwmboi Auxiliary 4 1953 SO11 2 Jun 2019
TP15266 Ben Barvas 2 1956 NC20 17 May 2022
TP16849 Biggin Farm 4 1957 NZ42 28 Mar 2021
TP17382 Bleak Hill 4 1954 SE22 22 Nov 2021
TP20335 Brith-Weunydd 4 1953 ST07 26 May 2019
TP8086 Brownsey Moor 3 1955 SE38 8 Oct 2022
TP19356 Bryn Du 4 1953 SO11 20 Jul 2018
TP23704 Burchetts Green 4 1952 TQ08 24 May 2015
TP17465 Busk Moss 3 1955 SE38 16 Aug 2020
TP19359 Craig-Y-Gilfach 4 1953 SO11 3 Jun 2018
TP19387 Cwmaman 4 1953 SO11 23 May 2022
TP25851 Cwmaman Auxiliary 4 1953 SO11 23 May 2022
TP17471 Easterside Hill 3 1955 SE38 21 May 2022
TP19360 Ffos-Y-Fran Reservoir 4 1953 SO11 8 Jun 2019
TP21679 Four Burrows 4 1955 SX07 16 Apr 2022
TP00057 Gallow Hill 3 1952 NS29 23 Apr 2022
TP20383 Graig Fach 4 1953 ST07 6 Sep 2014
TP19213 Graig Fawr 4 1953 SO11 21 Jul 2019
TP17473 Great Haw 3 1955 SE38 24 Feb 2019
TP7367 Great Yarlside 3 1961 NY71 30 Jul 1988
TP17474 Greets Hill 3 1955 SE38 9 Jan 2022
TP20397 Gwaelod-Y-Garth 4 1954 ST07 28 Oct 2019
TP17476 Harland Hill 3 1955 SE38 9 Mar 2019
TP7507 High Seat 3 1962 NY71 30 Jul 1978
TP17478 Ivy Scar 3 1955 SE38 3 Oct 2022
TP17479 Jingle Pot 3 1955 SE38 21 Nov 2021
TP17484 Knavy Knot 3 1955 SE38 15 Jan 2023
TP7379 Knipe Moor 3 1961 NY71 4 Mar 1990
TP17274 Ladysmith Camp 4 1952 SD80 25 Oct 2022
TP17480 Lodge Pasture 3 1955 SE38 21 Apr 2019
TP23701 Maidenhead Thicket 4 1952 TQ08 12 Apr 2015
TP17273 May Hill 4 1952 SD80 5 Nov 2022
TP17123 Middle Dale 3 1950 SD47 6 Feb 2020
TP17342 Middle Healey 4 1949 SE02 3 Aug 2020
TP17336 Millstone Rigg 4 1962 NY71 5 Sep 2017
TP17336 Moss Farm 4 1949 SE02 3 Mar 2021
TP25794 Mynydd Aberdar Auxiliary 4 1953 SO11 5 Jun 2019
TP19345 North Merthyr Quarry 4 1953 SO11 7 Jul 2018
TP20230 Polmenna 3 1949 SS30 17 Apr 2022
TP7306 Saddleback 3 1953 NY45 8 Apr 1977
TP7493 Sails 3 1962 NY71 30 Jul 1978
TP7368 Seat Robert 3 1961 NY71 4 Mar 1990
TP7307 Selside Brow 3 1961 NY71 5 Jun 1991
TP8083 Shaw 3 1955 SE38 17 Sep 2022
TP17275 Slatepit Moor 4 1952 SD80 25 Oct 2022
TP7380 Stonesdale Moor 3 1962 NY71 9 Aug 2005
TP17343 Stormer Hill 4 1949 SE02 15 May 2019
TP7506 Swarth Fell Pike 3 1962 NY71 19 Dec 1998
TP7818 Tees Head 3 1962 NY71 20 Aug 2011
TP19362 Twyn Croes 4 1953 SO11 3 Aug 2018
TP17453 Virgin Moss 3 1955 SE38 23 Feb 2019
TP17454 Wasset Fell 4 1955 SE38 22 Aug 2020

Since the number of rings emplaced is not known these stats may be not be based on a representative sample.

References

  1. The History of the Retriangulation of Great Britain 1935-1962
  2. email from Ian Wilson to the Trigonomy mailing list, 15 July 2009
  3. Email from Ian Wilson to the Trigonomy mailing list, 25 September 2013