Gunpowder and greenhouse: what they have in common

1. Step 1. Gunpowder — is used in — Cannon. A gunpowder charge.
2. Step 2. Cannon — uses — Casting. Barrels were cast.
3. Step 3. Casting — is used in — Window glass. The panes were cast in moulds.
4. Step 4. Window glass — is part of — Greenhouse. It lets light in and holds heat.

Open Evothings