Hat crown and mechanical clock: what they have in common

1. Step 1. Hat crown — is part of — Hat. The upper part.
2. Step 2. Hat — is made of — Felt. Felt.
3. Step 3. Felt — is material for — Piano. The hammers are covered with felt.
4. Step 4. Piano — uses — Tuning fork. Tuning.
5. Step 5. Tuning fork — is part of — Quartz clock. Quartz shaped like a tuning fork at 32,768 Hz.
6. Step 6. Quartz clock — evolved from — Mechanical clock. Quartz clocks replaced mechanical ones: a vibrating quartz crystal took the place of the pendulum and balance.

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