Wall mirror and newcomen engine: what they have in common

1. Step 1. Wall mirror — is made of — Silver. Silvering.
2. Step 2. Silver — is material for — Syringe. Early needles were silver.
3. Step 3. Syringe — has part — Piston. A plunger.
4. Step 4. Piston — is part of — Newcomen engine. Atmospheric pressure moves the piston.

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