Mercury cistern and smart meter: what they have in common

1. Step 1. Mercury cistern — is part of — Barometer. An open reservoir.
2. Step 2. Barometer — is made of — Mercury. A column of mercury.
3. Step 3. Mercury — is material for — Clinical thermometer. Mercury expands when heated.
4. Step 4. Clinical thermometer — evolved into — Digital thermometer. A replacement for the mercury thermometer.
5. Step 5. Digital thermometer — has part — Liquid-crystal display. The reading is on an LCD.
6. Step 6. Liquid-crystal display — is part of — Smart meter. A display.

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