Wheal Unity Despite the reduction in pumping charges which resulted from their being linked to the County Adit, not all the mines thus served proved equally successful. Among the richest was Wheal Unity from which, in the years 1792-98, the adventurers' part of the ore (after dues had been deducted) amounted in value to £197,573 and realised a profit of £101,604.
1819, Wheal Unity had been sunk to 144 fathoms below the deep adit, and was equipped with three steam engines of 60, 58 and 52 in. cylinders.
St Just Area Mines, Cornwall