The mine exploited four copper lodes running south-east along the coastline, into the cliff and out beneath the seabed of Mount's Bay. About 160 men were employed at its peak - a small operation by Cornish standards, but well placed on geology that paid. The output figure of 17,500 long tons across just twelve years tells you that Wheal Trewavas was a productive venture, not a speculative failure. Cornish copper, like Cornish tin, fed the industrial revolution that the county itself had pioneered. The ore came up, was crushed and dressed on platforms above the cliffs, and went by road to the smelters at Hayle or Swansea. Then in 1846 the operation ended. The reasons were the usual Cornish ones - exhausted lodes, falling prices, water that the pumps could not handle, the capital moving on to mines elsewhere - but the abruptness is striking. After 1846 nobody worked here again.

The engine house and chimney of Old Engine Shaft are situated on the cliffside, twenty metres above the sea and forty metres from the clifftop. To reach them you scramble down a steep grass slope from the coast path; the engine house perches on a narrow shelf above a vertical drop, the chimney standing separately a few yards away. Beside the engine house is a capstan platform - the level area where, during the operation of the mine, a manually operated capstan was used to lower equipment down the shaft. Imagine that work. The capstan turned by men putting their backs against bars, on a platform with no railing, hauling Cornish boilers and pump rods up and down a shaft sunk through the cliff face and on under the seabed. The chimney here was rebuilt around 1840 to replace an earlier one - a small detail that hints at how exposed the masonry was to weather coming straight off the Atlantic.

A short distance further east along the coast stands the second pair of ruins - the engine house and separate chimney of New Engine Shaft, near the top of the cliff rather than on its face. Both are Grade II listed. The shaft they served went deeper than the first and pushed the workings further out beneath the bay. Cornish engine houses are easy to read once you know what to look for. The tall, rectangular tower held a Cornish beam engine - a vertical steam cylinder under the roof, a great cast-iron rocking beam projecting through a thick wall at the top, and a pump rod descending into the shaft through a wooden head-frame outside. The chimney stood separately so its draft would not interfere with the engine. Both engine and chimney were tied together by a maze of flat-rod linkages and connecting structures that have long since rotted or rusted away. What remains is the bones.

Wheal Trewavas is a Scheduled Monument and forms part of the Cornwall and West Devon Mining Landscape inscribed by UNESCO as a World Heritage Site in 2006. The inscription recognises that Cornwall, between roughly 1700 and 1914, was the most technologically advanced mining region on Earth - the place where deep mining, steam pumping, and ore dressing reached an industrial scale and from where Cornish know-how spread out to copper and tin and gold camps in Mexico, South Australia, South Africa, and the western United States. "Cousin Jack" mining engineers and "Cousin Jenny" women, leaving Cornish villages, taught the rest of the world how to dig deep and pump dry. The two ruins on the cliff at Trewavas are part of that story - a small operation, productive while it lasted, beautifully placed, and now consumed by the slow argument between Atlantic weather and Victorian masonry. Walk the coast path here in winter and the spray reaches the chimneys.