After the black tin, or ore, had been thus treated
it was conveyed to the blowing-house. The usage
on Dartmoor was, when a miner was far from one of
these, to tie the ore in a bag marked with his name
or sign, and hang it about a dog's neck; the beast
then conveyed it to the mill.
Of the "blowing-houses" a great many remain on Dartmoor. There are two on the Yealm, one, very perfect, on the Erme, one very early, before the introduction of the waterwheel, at Deep Swincombe, several on the Dart.
The blowing-house was a small structure of one chamber and a cache, or storeplace, underground. The doorway was rarely high enough to admit a man without stooping double. The walls were of stone without mortar, and, as far as can be judged from their remains, had no window. The furnace was heated with charcoal, and the fire blown by means of a great pair of bellows worked by a tiny waterwheel. The process was so roughly conducted that "divers light sparkles" of tin are said to have lodged in the thatched roof in sufficient quantities to render the burning of the roof once in seven years worth the undertaking. The melted metal ran out into a spoon-shaped hollow in a block of granite, or elvan, and was run into moulds also cut in slabs, many of which remain near the old blowing-houses.
The white tin was then conveyed to a royal smelting-house, where it received a stamp; and no miner was suffered to dispose of his metal till it had thus been marked, and he had paid his due to the Crown for it.
