Small arc scale and zip: 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 — is made of — Bronze. Quadrants are bronze or wooden.
5. Step 5. Bronze — is material for — Hook and eye. Medieval fasteners were bronze.
6. Step 6. Hook and eye — evolved into — Zip. Judson started with a chain of hooks.

Open Evothings