Automatic block signalling and newcomen engine: what they have in common

1. Step 1. Automatic block signalling — has part — Railway semaphore. Signals.
2. Step 2. Railway semaphore — evolved into — Traffic light. The first traffic light was a railway-style semaphore.
3. Step 3. Traffic light — uses — Coal gas. A gas lamp lit the signal.
4. Step 4. Coal gas — is made of — Coal. The gas was made by the dry distillation of coal.
5. Step 5. Coal — uses — Coal mine. Extraction.
6. Step 6. Coal mine — is used in — Newcomen engine. Pumping water out of mines.

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