Mortar batteries, of which North battery is shown, were hidden underground
inside the fort, with only a small aperture to fire through, allowing
defenders to lob projectiles in relative safety, but making it nearly
impossible for any attacker to hit these defences.
The mortars shown are 13-inch iron mortars, with a range of about 1000
yards these were intended to prevent attackers from ever reaching the fort
by killing them at a distance
