Military radio battery pack and archimedes’ screw: what they have in common

1. Step 1. Military radio battery pack — is part of — Military radio. Power.
2. Step 2. Military radio — uses — Cipher machine. Encryption.
3. Step 3. Cipher machine — has part — Gear. Wheels set the cipher.
4. Step 4. Gear — is part of — Sakia. A gear drive from the animal to the wheel.
5. Step 5. Sakia — is used in — Irrigation. Sakias in Egypt and India.
6. Step 6. Irrigation — uses — Archimedes’ screw. The Archimedes’ screw lifted water for irrigation.

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