This photograph 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.
Burnard comments on the photograph that 'this is probably one of the most ancient moulds' that he had seen on Dartmoor.
Image - Glass Plate