 The remains of over 40 blowing houses have been identified on Dartmoor.The blowing house method of smelting tin was probably introduced early in the 14th century to replace the earliest method of smelting which had to be done in two stages – a first smelting probably took place near to the tinworks and the roughly smelted metal was taken to a stannary town to be smelted again to produce the final refined product.Each of these smeltings was taxed separately until 1303 when they were replaced by a single tax on the finished product.