Tin mining on the Wheal Owles sett in St Just has a long history with records dating back into the 15th century. By 1893 the Wheal Owles mine was working a vastly extended group of setts running from the Atlantic cliffs as far inland as Tregeseal. The amalgamated properties included a number of abandoned mines, multiple ore processing sites, shafts and many miles of levels both under the land and under the sea. By the 1890s all mining activity was concentrated at the western or seaward end of the property where the old Cargodna section had been restarted in 1884 when the Wheal Drea section was abandoned. At this time the mine had about 100 underground workers.
On 10th January 1893 about 40 men and boys were underground, having descended the Cargodna Shaft which lies part way down the cliff below the Wheal Edward engine house. A cross-cut was being driven at 65 fathoms, at 8.45am charges were fired and a huge volume of water poured into the level, sweeping all before it and then passing down into the deeper levels. The miners on the 65 were all killed while men in other locations faced a desperate race against time to get up the ladders faster than the rising water.
In all 19 men and a boy were killed. Their names are inscribed on a stone by the West Wheal Owles pumping engine house. They were killed because the mine plans were inaccurate and showed 19 fathoms of ground between the blasting position and the abandoned and flooded levels of Wheal Drea. The plans indicated two distinct lodes, Cargodna and Drea, with solid ground between them but in fact the two lodes had run together to become one but the coming together of the lodes had not been picked up by the surveyor because he had not made allowance over many years for the variation in magnetic north.
Wheal Owles was essentially the private mine of the Boyns family who had supplied pursers, officials and services such as haulage and surveying to the mine ever since the reopening in 1834. In 60 years the mine had had but two pursers, John Boyns and his son Richard, who by 1891 was being helped in his office by his John Herbert. The surveyor who failed to make allowance for magnetic variations was Richard Boyns, by now a sick old man who was devastated by what had happened. Richard Boyns had learnt his trade on the job, he had been manager and purser since 1855 and his education had largely taken place in the days before any form of inspection regime or proper training. It emerged that he was not aware that allowance had to be made for magnetic variation.
The Wheal Owles disaster clearly shows the importance of proper regulation, regular inspection and effective training in the safe conduct of inherently dangerous businesses. Richard Boyns' failure as a surveyor was a direct consequence of the failure of the regulatory regime and the twenty men who died were the victims of this failures, they were failed by the inspectorate as much as they were by Richard Boyns.