Tugboat and bellows: what they have in common

1. Step 1. Tugboat — has part — Paddle wheel. The first tugboats were paddle-driven.
2. Step 2. Paddle wheel — works like — Water wheel. A water wheel in reverse: instead of water turning the wheel, the wheel pushes the water.
3. Step 3. Water wheel — is used in — Rolling mill. The first mills were turned by water.
4. Step 4. Rolling mill — is part of — Steel works. Rolling mills.
5. Step 5. Steel works — has part — Blast furnace. Blast furnaces.
6. Step 6. Blast furnace — has part — Bellows. Air was blown in by bellows, later by blowers.

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