I have finally found all the material, that 'vanished' when my PCs broke down.
Here is Thomas Curtis, renowned for re-opening the Wherry Mine in 1778.
Said to have been a poor farmer/miner from Breage, though may be of Perranuthnoe.
He was born in 1721. In 1750 (age 29) he had married the widow Elizabeth Varker.
Age 57, he took it ito his head to be an Adventurer in the tin mining industry.
Formerly the mine was opened as a shore dig, when tides allowed.
His bold plan was to fully excavate the Elvan Dyke for its Cassiterite.
He died in 1791, age 70, before the mine worked at its full potential.
He had dug the shaft personally, forming the caulked timber tower to allow deeper digging.
The mine was then taken over by Thomas Gundry (and others), who appear to be merchant bankers.
Until then the mine had been worked using a light flat bottomed boat to carry the ore to the shore. The boat was a wherry, a boat design more familiarly seen on the East Coast.
I suspect in conversation, some visiting Lowestoft fisherman had given Thomas Curtis the idea of just how to sail over the low reefs.
In 1792 Thomas Gundry had decided to form a trestle bridge to carry the ventilation and donkey sacks.
The mine working was destroyed in 1798 by an American vessel, which had broken its moorings in Gwavas Lake, during a storm.
The painting is said to be by Opie. Owned then by Dr Symons.