Carro e optical telegraph: o que têm em comum

1. Passo 1. Carro — faz parte de — Wagonway. Wagons rolled on the rails.
2. Passo 2. Wagonway — evoluiu para — Railway track. Cast-iron and steel rails replaced wooden ones.
3. Passo 3. Railway track — inspirou — Time zones. Introduced because of railway timetables.
4. Passo 4. Time zones — utiliza — Electrical telegraph. Synchronizing time by telegraph.
5. Passo 5. Electrical telegraph — evoluiu de — Optical telegraph. The electrical telegraph replaced semaphore lines.

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