Oblique cuts of the citadel rock toward the sea
A schedule of cuts, measured in braccia and keyed to the compass, works toward a single universal cut
In faint red chalk and mirror script, this page (folio 30 verso) plans how to cut the rock beneath a seaside citadel. A schedule of oblique cuts, measured in braccia and keyed to the compass points, works toward a single 'universal cut,' while a note sets the wall to face south under cover of the line behind it. Leonardo observes that the sea beats and ruins the base of the mountain, and reasons that cutting and smoothing the slope would let the fallen debris build an embankment. Terrain profiles are sketched across the lower half of the sheet.
On this page
The wall opens south, shielded by the wall behind
A note beside the figure sets the face fully to the south and not to the west, because the wall that follows behind it gives cover. The orientation is chosen so that the defensive line screens the exposed side.
A schedule of oblique cuts, ending in the universal cut
The right-hand column lists a first through fourth oblique cut by compass bearing, with measures of 100 and 1100 braccia and the fourth set beneath the citadel at half obliquity. The final cut, oblique to the south at less than half obliquity, is declared 'our universal cut.'
The sea beats and ruins the foot of the rock
Where the cuts run confused in every direction, the sea beats against and ruins the mountain. By cutting and smoothing the slope, Leonardo reasons, the fallen debris would itself form an embankment at the base of the rock.
Red-chalk profiles of the coastal hill
Faint red-chalk sketches trace hillside contours and a low terrain profile across the middle and lower sheet, illustrating the mass of rock to be cut. No lettered points accompany these profiles.