Courtesy of the fact that I forgot to buy the chews that Rosie likes, and so had to pop to the shop next door. The engine house was once home to a pumping engine, and the shaft behind it is labelled rather engagingly : 'Matthew's Mine'. It was mostly a tin and copper mine, but also offered some wolfram, molybdenum, lead, silver, and of course the eternal arsenic.
It was originally a long "gunnis" or open cutting, only later being extended into an underground mine, which is apparently a sign of great age. The gunnis is no longer visible, having been filled in in the 1950s.
A parish website, calstock.info claims it was "worked from the 11th Century to 1905 (also 1909-10), with periods of closure." The Heritage Gateway is a bit more conservative, describing it as post-medieval and dating from 1540 AD. There are some nice quotes about it:
"An advertisement dated 22/7/1793 in the Sherborne Mercury mentions a forthcoming "survey for setting of tribute (in four parts), the valuable mine of Drake, or Drake's walls...has been worked for upwards of a century ....annually produced a large quantity of the richest tin...never known to fail...upwards of £1100 worth of ore has been raised in the course of this last year by 18 or 20 men". "
"From the West Briton, 2 March 1866, "At Drakewalls Mine, work having been refused to men connected with the newly formed society, the men in a body refused to work, and having caught one of their number who had expressed his willingness to go below, rode him on a rail through Gunnislake."
In 1889, two men, Bant and Rule, were trapped in the mine by falling sand for several days. The miners used *small blasts of dynamite* to excavate a channel down to the entombed men. When they finally made contact with the trapped men: "strong men, many of whom had been in rough mining camps in all parts of the world, (were) alternately laughing and crying, like children, with emotion."
After enlargement of the hole, one Tom Chapman was lowered down and managed to rescue them. Bant and Rule were fed "soup, beef tea &c."
It sounds like it was a huge mine by the time it was finally closed. When it was re-opened in 1901, it took nearly two years of steady pumping to unwater it. "Below, so much ground has been taken away that great underground caverns exist which can be traversed only by boat". There's a fun thought for all the people who live on top of those 'great underground caverns'.
After all that pumping, it must have been a great disappointment when it proved not worth the effort, and closed again for the last time in 1910.