Airport and gas lamp: what they have in common

1. Step 1. Airport — has part — Jet bridge. Jet bridges.
2. Step 2. Jet bridge — has part — Hydraulic cylinder. Raising the bridge.
3. Step 3. Hydraulic cylinder — is used in — Tunnelling shield. The shield was pushed forward by jacks.
4. Step 4. Tunnelling shield — is used in — Tunnel. Shield tunnelling.
5. Step 5. Tunnel — has part — Street light. Lighting.
6. Step 6. Street light — evolved from — Gas lamp. Gas lamps.

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