This photograph was taken during 1887. It shows evidence of the tin mining industry which operated on Dartmoor until around 1939.
Blowing houses (sometimes called blowing mills) contained small blast furnaces into which a forced draught of air was blown using waterwheel-powered bellows. Cassiterite (tin oxide) ore was smelted in the blast furnace and cast into ingots using a mould stone.
This is the ruins of Wheal Prosper with the Walkham valley behind and the line of the Prison Leat on the far hillside.