Hourglass neck and incandescent light bulb: what they have in common

1. Step 1. Hourglass neck — is part of — Hourglass. A narrow neck sets the rate.
2. Step 2. Hourglass — works like — Water clock (clepsydra). The same principle of timing by outflow, with sand instead of water.
3. Step 3. Water clock (clepsydra) — is made of — Stone. The clepsydra from Karnak is a stone vessel.
4. Step 4. Stone — is material for — Oil lamp. The first lamps were stone bowls (Lascaux).
5. Step 5. Oil lamp — evolved into — Incandescent light bulb. The electric lamp replaced oil and gas lamps.

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