Barrel heads and electrical grid: what they have in common

1. Step 1. Barrel heads — is part of — Barrel. End caps.
2. Step 2. Barrel — works like — Arch. Staves squeezed by hoops hold their shape by the same compression as the stones of an arch.
3. Step 3. Arch — is made of — Brick. Arches were built of brick or stone.
4. Step 4. Brick — is material for — Power station. The buildings of the first power stations were brick.
5. Step 5. Power station — is part of — Electrical grid. Power stations feed the grid.

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