Optical telegraph and cannon: what they have in common

1. Step 1. Optical telegraph — uses — Lens. Signals were read through telescopes.
2. Step 2. Lens — is part of — Sextant. The sextant’s telescope.
3. Step 3. Sextant — is part of — Sailing ship. The sextant and chronometer were a sailing ship’s navigation kit for finding latitude and longitude.
4. Step 4. Sailing ship — includes — Galleon. A sailing ship.
5. Step 5. Galleon — has part — Cannon. Cannons on the decks.

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