Steel shield shell and incandescent light bulb: what they have in common

1. Step 1. Steel shield shell — is part of — Tunnelling shield. A steel cylinder that holds back the ground.
2. Step 2. Tunnelling shield — is used in — Tunnel. Shield tunnelling.
3. Step 3. Tunnel — has part — Street light. Lighting.
4. Step 4. Street light — evolved from — Gas lamp. Gas lamps.
5. Step 5. Gas lamp — evolved into — Incandescent light bulb. Electricity displaced gas lighting.

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