Meridian Stone

FALMOUTH

843-1/0/10016 FALMOUTH HOSPITAL 09-JUL-08 MERIDIAN STONE

II Meridian stone erected in 1837 by the Royal Cornwall Polytechnic Society. Large dressed block of granite with narrow chamfered step. The stone has four principal faces and a flat top with a small central hole. Each face bears an inscribed letter representing the principal points of the compass.

History: The stone was positioned on the meridian leading through St Keverne Church tower to provide a calibration tool for miners' surveying compasses known as dials. Magnetic north varies through time and therefore any surveys generated using only magnetic readings would be subject to an increasing degree of error, which in a mining context could be fatal. As a measure to reduce the inaccuracies, the Society erected this stone. Mining surveyors placed their dials in or over the hole in the centre of the stone and aligned the device precisely on St Keverne Church tower. By this means the difference between true and magnetic north could be measured and the dial calibrated accordingly. In subsequent years it was discovered that there were also difference between magnetism at the surface and underground and the stone may therefore 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".

SOURCES Williams, J.B., Practical Geodesy, (1855), 193-205. Hoskold, H.D., A practical treatise on mining, land and railway surveying, engineering, &c., (1863), 1-7. http://gge.unb.ca/PhotoAlbum/1996/Jack/JackPillar.gif Accessed 28th May 2008 http://gge.unb.ca/MT/Events/Commemoration.pdf Accessed 28th May 2008

REASONS FOR DESIGNATION DECISION The Falmouth Meridian Stone, is designated at Grade II for the following principal reasons: * The stone survives well in its original position * The stone retains its line of sight to St Keverne Church tower * The stone played an important role in the development of compass calibration * It may be the earliest surviving survey related base station * It is associated with the internationally important C19 Cornish mining industry * It represents tangible evidence of scientific philanthropy