Small arc scale and plumbing: what they have in common

1. Step 1. Small arc scale — is part of — Davis quadrant. A scale for large angles.
2. Step 2. Davis quadrant — evolved from — Jacob’s staff. Davis spared the navigator from looking at the Sun.
3. Step 3. Jacob’s staff — works like — Quadrant. Two angle gauges for measuring the altitude of celestial bodies.
4. Step 4. Quadrant — uses — Universal gravitation. The angle is read against a plumb line.
5. Step 5. Universal gravitation — is used in — Water tower. Pressure from height.
6. Step 6. Water tower — is part of — Plumbing. Maintaining pressure.

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