Turnstile and incandescent light bulb: what they have in common

1. Step 1. Turnstile — is part of — Metro. Turnstiles.
2. Step 2. Metro — uses — Tunnel. Tunnels.
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.

Open Evothings