Meridian Stone is a Grade II listed building in the Cornwall local planning authority area, England. First listed on 9 July 2008. Stone.
Meridian Stone
- WRENN ID
- ruined-passage-foxglove
- Grade
- II
- Local Planning Authority
- Cornwall
- Constituency
- Truro and Falmouth MP: Jayne Kirkham (Lab)
- Country
- England
- Date first listed
- 9 July 2008
- Type
- Stone
- Address
- Meridian Stone, Falmouth Hospital
- OS grid reference
- SW 795 329
- Coordinates
- 50.15578, -5.08684
- Source
- Historic England listing
Description
This is a granite meridian stone erected in 1837 by the Royal Cornwall Polytechnic Society. It is a large, dressed block of granite with a narrow, chamfered step. The stone has four principal faces and a flat top with a small central hole. Each face is inscribed with a letter representing the principal points of the compass.
The stone was positioned on a meridian line running through the tower of St Keverne Church and served as a calibration tool for miners’ surveying compasses, known as dials. Magnetic north varies over time, and surveys reliant solely on magnetic readings would accumulate errors, which could be dangerous in a mining context. The Society erected this stone to mitigate these inaccuracies. Mining surveyors placed their dials in the hole in the stone’s centre and aligned them with the church tower to measure the difference between true north and magnetic north, thereby calibrating the dial. It was later discovered that magnetic variations also existed between the surface and underground, suggesting the stone may have been used for a relatively short period.
A plaque, formerly attached to the western face, read: "This pillar was erected in the Meridian of St Keverne by The Royal Polytechnic Society of Cornwall in the year 1837."
Local climate
Meridian Stone receives an average of 850 mm of rain a year. This makes it wetter than 59% of listed buildings in the UK. Its exposure to wind-driven rain is greater than that of 84% of listed buildings.
It experiences an average of 7 freeze-thaw cycles a year, fewer than 95% of listed buildings. Of these, 3 follow at least 1 mm of rain in the preceding 48 hours. Average temperatures at this location have risen by 0.3°C per decade since 1991.
Averages for 1991–2020; temperature trend 1991–2025. Figures describe the wider area (a grid cell of roughly 10 km), not the individual site. Contains modified Copernicus Climate Change Service information 2026.
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