Ravelins and crossing lines of artillery fire
How paired embrasures break a ravelin, and why distance changes how it is struck
Four notes on fortification, illustrated by geometric diagrams of crossing lines of fire, triangles inscribed in circles, cones and a small pyramid. Leonardo warns against building conveniences inside fortress walls that a captured enemy could exploit, explains how paired embrasures labelled h, K and l, b break up a whole ravelin from cuts in the ditch banks, and observes that a ravelin is struck more by transverse fire the farther it stands from its fortress. He adds that all the oblique bevels of the outer banks and of the ravelins should command the fortress's gun-embrasures. Further untranscribed notes in mirror script are also present.
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Paired embrasures break the ravelin
The two mouths h and K, and the two l and b, break up the whole ravelin. These embrasures are planted in the cuts made in the banks of the ditch, labelled l h - b K - r c - n a.
Distance and transverse fire on the ravelin
The site a will never be touched by any artillery percussion. The farther a ravelin lies from its fortress the more it is struck by transverse motions of fire, and conversely it is struck less the nearer it stands to that fortress.
Oblique bevels command the embrasures
No convenience should be left inside the walls of fortresses by which enemies who have seized those walls might descend. All the oblique bevels of the outer banks, and likewise of the ravelins, should oversee the gun-embrasures of the fortress.
Crossed lines of fire and inscribed triangles
The upper part of the sheet is worked out with crossing straight lines, triangles inscribed in circles and cones, tracing how fire and sightlines meet. A small pyramid is drawn at the right.