This photograph is dated 7 March 1888. 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 the mould stone.
Image - Black and White Print