The Scottish Mountain Heritage Collection
1660.2022.1(a-b)
O.S bench marks - Plaque and Bolt
11/05/2022
Hermione Cooper
11/05/2022
Brass rectangular plaque and mushroom shaped bolt.
Brass
Plaque - 19(L) x 10(W) x 9(H) cms Bolt - 10(H) x 7(W) cms
2
On bolt “ O.S.B.M”
On plaque “O M S BGM. 1062”
Gold, black
UK
Bench Marks were used in the Principal Triangulation of Britain which was carried out between 1791 and 1853; the object being to produce maps, initially for use in military campaigns, though in the absence of any major conflicts in the UK, more peaceful uses have been found in leisure activities, planning and ecological studies.
The bench marks ( from which we draw the modern phrase) were attached to solid structures such as buildings and bridges, with their height calculated from a mean datum line. They could then be used to calculate other heights using sightings and measurements taken with theodolites.
GPS technology has rendered Bench Marks obsolete though many remain in place and there is an OS map showing their location. Some marks are chiselled into stone and there are wall plaques, bolts and rivets. We have a couple of excellent examples here in the collection.
Both the plaque and bolt were found beside demolished bridges on the A82 road in Inverness - shire, Scotland.
Curiously the plaque has BGM rather than BM and more curiously the Ordnance Survey don’t know why - help please!
The bolt doesn’t seem to have a number - another curiosity!
Much more info on the OS website…check it out.
11/05/2022
11/05/2022
Spectrum : UK Museum documentation standard, V.3.1 2007
11/05/2022