Pesticide and barrel: what they have in common

1. Step 1. Pesticide — uses — Aerosol can. In 1941 insecticide began to be sprayed from aerosol cans, the "bug bombs" made for soldiers; after the war the same can was used for hair spray.
2. Step 2. Aerosol can — uses — Pressure. A propellant gas.
3. Step 3. Pressure — is used in — Column. It works in compression.
4. Step 4. Column — is made of — Brick. Stone columns.
5. Step 5. Brick — is material for — Arch. Arches were built of brick or stone.
6. Step 6. Arch — works like — Barrel. Staves squeezed by hoops hold their shape by the same compression as the stones of an arch.

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