Inner Works of a Keep and Mortar-Proof Bastions
Machicolated platforms, a vented powder-store, and low bastions with obtusely beveled vaults
Folio 93v, continuing text carried over from folio 94r, details the inner works of a keep. Leonardo sets small platforms with portcullises and machicolations at the room-entrances for pouring boiling water and fire on intruders, vents the tower open above its powder-store so an enemy charge cannot burst it, places exits opposite the magazine, and raises the cellar window against back-flooding of the ditch water; rooms a small tower cannot hold are tucked low into the counterforts out of the bombards' reach. The bastions are to be low and thick, roofed with an obtusely beveled vault to deflect glancing shot and lined inside with an acute-angled oak shelter, so that if a mortar breaches the vault the balls roll harmlessly between vault and shelter, with the embankments raised level with the vault's springing. Profile and bird's-eye sketches of a bastion tower, labelled tower of the burchioni and ditches, accompany the note.
On this page
Machicolated platforms and a vented powder-store
At the room-entrances of the rock's summit are little platforms carrying portcullises and machicolations, from which to throw boiling water and fire on any enemy within. The tower is left open above so that powder set by the enemy, if fired, cannot burst it, and its exit lies opposite the entrance where the powder-store stands.
Cellar window against back-flooding; rooms in the counterforts
The cellar window is set high so that if someone shuts off the outlet of the ditch water it cannot back up through the window and drown the wine and firewood. When a small tower cannot hold the necessary rooms, the missing ones are built low into the counterforts, beneath the reach of the bombards.
Low bastions with obtuse vaults and inner oak shelters
The bastions are low and thick, covered with a thick vault beveled at a strong obtuse angle to deflect transverse blows, and lined inside with a strong acute-angled timber shelter. If mortars break the vault, the timber protects what lies beneath and the balls roll between the broken vault and the shelter's springing, while the embankments rise level with the vault that roofs the bastions.
Profile of a bastion tower (tower of the burchioni)
Sketches show a low bastion tower in profile and in bird's-eye, with its ditches. One figure is captioned tower of the burchioni and another marks the ditches.