Great County Adit, Mining tunnel system in Cornwall, England
The Great County Adit extends over 40 miles underground through Cornwall, forming an intricate network of drainage tunnels for numerous mines.
Construction of this drainage system began in 1748 under John Williams' management at Poldice mine, expanding to serve more than 100 mining operations.
The engineering methods employed in the Great County Adit demonstrate the technical expertise developed by Cornish miners during the industrial revolution period.
Water continues to flow through the tunnel system, discharging approximately 500,000 gallons daily into the Carnon River from its portal near Twelveheads.
At its peak in 1839, the drainage system released 14.5 million gallons of water daily, utilizing more steam engines than all of continental Europe and America combined.
Location: Cornwall
GPS coordinates: 50.23440,-5.14000
Latest update: March 6, 2025 07:28
Carnon viaduct
2.7 km
Church of Saint Piran
3.4 km
Church of Saint Paul
2.5 km
Church of Saint Wenappa
2.9 km
Former Church of All Saints
3 km
St Michael's Church
1.7 km
The Rambling Miner
2.8 km
Gwennap Mining District with Devoran and Perran and Kennall Vale
722 m
Tower of Church of Saint Wenappa
2.9 km
Milestone At Sw 764450 Ne
3.2 km
Clock Tower And Boundary Wall
3.2 km
Milestone C. 300M North Of Sunny Corner Farm
3.5 km
Milepost On West Side Of B 3298 At Sw 733 427
2.9 km
Milestone Adjoining Garden Wall Of No 21
2.8 km
Milepost On West Side Of B3298 At Sw 730 412
3.2 km
Unity Wood Mine Magor's Pumping Engine House
3 km
Parish Boundary Stone At Sw 744429 Sw (Between Original Chacewater And Gwennap Parishes)
2 km
Milestone At Sw 766 386 Ne
3.3 km
Holy Well Of Saint Piran At Sw 778 387 Ne
3.6 km
Parish Boundary Stone At Sw 742429 Sw (Between Original Chacewater And Gwennap Parishes)
2.2 km
Parish Boundary Stone At Sw 747429 Sw (Between Original Chacewater And Gwennap Parishes)
1.7 km
Parish Boundary Stone At Sw 748429 Sw (Between Original Chacewater And Gwennap Parishes) (number 56)
1.7 km
Parish Boundary Stone At Sw 747429 Sw (Between Original Chacewater And Gwennap Parishes)
1.8 km
Parish Boundary Stone At Sw 744429 Sw (Between Original Chacewater And Gwennap Parishes)
2 km
Unity Wood Mine Winding Engine House
3.1 km
Toll House At Sw 781 398 Ne
2.9 km
Milestone, Pengreep, by entrance to Pengrean, just before bend
3.3 km
Milestone, Comford, on the fast narrow climb heading S, 10m NW of the public footpath
3.3 kmReviews
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