Means of communication and saw: what they have in common

1. Step 1. Means of communication — includes — Optical telegraph. A means of communication.
2. Step 2. Optical telegraph — uses — Lens. Signals were read through telescopes.
3. Step 3. Lens — is part of — Cinématographe. A lens.
4. Step 4. Cinématographe — has part — Crank. The film was advanced by turning a handle.
5. Step 5. Crank — is part of — Sawmill. A crank turns the wheel’s rotation into the stroke of the saw.
6. Step 6. Sawmill — uses — Saw. The cutting tool is a saw.

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