Trowel and electric motor: what they have in common
- Step 1. Trowel — is used in — Brick. Bricklaying with a trowel.
- Step 2. Brick — is material for — Metro. The vaults of the first tunnels are brick.
- Step 3. Metro — uses — Electric locomotive. The first lines were steam-operated; electric trains since 1890.
- Step 4. Electric locomotive — has part — Electric motor. Traction motors.