Cart and optical telegraph: what they have in common

1. Step 1. Cart — is part of — Wagonway. Wagons rolled on the rails.
2. Step 2. Wagonway — evolved into — Railway track. Cast-iron and steel rails replaced wooden ones.
3. Step 3. Railway track — inspired — Time zones. Introduced because of railway timetables.
4. Step 4. Time zones — uses — Electrical telegraph. Synchronizing time by telegraph.
5. Step 5. Electrical telegraph — evolved from — Optical telegraph. The electrical telegraph replaced semaphore lines.

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