Wall heating flues and parachute: what they have in common

1. Step 1. Wall heating flues — is part of — Hypocaust. Pipes in the walls for hot air.
2. Step 2. Hypocaust — uses — Convection. Hot air under the floor.
3. Step 3. Convection — is used in — Hot air balloon. Hot air rises and fills the canopy.
4. Step 4. Hot air balloon — is made of — Silk. The Montgolfier balloon was fabric lined with paper.
5. Step 5. Silk — is material for — Parachute. The canopy is silk.

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