Incandescent light bulb and bell: what they have in common

1. Step 1. Incandescent light bulb — evolved from — Gas lamp. Electricity displaced gas lighting.
2. Step 2. Gas lamp — has part — Gas burner. A coal-gas burner.
3. Step 3. Gas burner — is part of — Hot air balloon. It heats the air in the envelope with a propane flame.
4. Step 4. Hot air balloon — uses — Archimedes’ principle. Warm air is lighter than cold — Archimedes’ principle in the atmosphere.
5. Step 5. Archimedes’ principle — is used in — Diving bell. Sinking with ballast.
6. Step 6. Diving bell — has part — Bell. A body open at the bottom.

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