This photograph is dated 27 December 1887. It shows evidence of the tin mining industry which operated on Dartmoor until around 1939.
It is of the southern blowing house on the Plym near Plym Steps. Leather Tor and Sharpitor in distance.
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.