Traffic light and piston pump: what they have in common

1. Step 1. Traffic light — uses — Coal gas. A gas lamp lit the signal.
2. Step 2. Coal gas — is made of — Coal. The gas was made by the dry distillation of coal.
3. Step 3. Coal — uses — Coal mine. Extraction.
4. Step 4. Coal mine — is used in — Newcomen engine. Pumping water out of mines.
5. Step 5. Newcomen engine — has part — Piston pump. The beam drove a mine pump.

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