Mercator projection and rock drill: what they have in common

1. Step 1. Mercator projection — is used in — Sailing ship. Navigating along straight rhumb lines.
2. Step 2. Sailing ship — is used in — Seaport. A port receives ships.
3. Step 3. Seaport — has part — Lighthouse. A lighthouse.
4. Step 4. Lighthouse — has part — Rotation mechanism. It rotates the optics, setting the flash pattern.
5. Step 5. Rotation mechanism — is part of — Rock drill. It rotates the rod between blows.

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