Abacus beads and vacuum pump: what they have in common

1. Step 1. Abacus beads — is part of — Abacus. Movable beads — the places of a number.
2. Step 2. Abacus — is made of — Stone. Counting was done with pebbles — the Latin calculus.
3. Step 3. Stone — is material for — Blast furnace. The shaft of a blast furnace is stone.
4. Step 4. Blast furnace — has part — Bellows. Air was blown in by bellows, later by blowers.
5. Step 5. Bellows — has part — Check valve. An air intake valve.
6. Step 6. Check valve — is part of — Vacuum pump. Valves stop air from flowing back.

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