Gutter and bellows: what they have in common

1. Step 1. Gutter — is made of — Stone. Ancient gutters were stone or ceramic channels.
2. Step 2. Stone — is material for — Blast furnace. The shaft of a blast furnace is stone.
3. Step 3. Blast furnace — has part — Bellows. Air was blown in by bellows, later by blowers.

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