Earth-filled fortification walls against artillery
Triangular-section ramparts packed with moist earth, with a red-chalk hill profile and a counterweighted frame
Pen diagrams show ramparts of triangular section, lettered o p, a b and n m, whose inner mass a b is to be filled with moist, well-tamped earth mixed with chopped brushwood. Leonardo makes the wall n o pyramidal so the earth can be retained after artillery has stripped away the outer faces, adding that the walls be filled inside so horses may stand within. A red-chalk profile of a hill and a small frame carrying a counterweight complete the sheet.
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Pyramidal walls to survive artillery (o p, a b, n m)
The walls are drawn in triangular section and lettered o p, a b, n m, with the wall n o tapered to a pyramidal profile. This is done so that the earth a b can be held up after artillery has thrown down the outer faces of the walls.
Moist earth fill mixed with brushwood
The core a b is to be packed with earth used as filling for the walls of the strongholds. The earth should be moist and well tamped, as for earthen house walls, and mixed with chopped brushwood or other thin wood; the walls are filled inside so that horses may stand there.
Red-chalk profile of a hill
A soft red-chalk (sanguigna) line sweeps across the top of the sheet as the profile of a hill. It sits above the pen work as a preparatory landscape note.
Frame with counterweight
A slender frame drawn in red chalk carries a hanging counterweight. The caption labels it simply as a frame with a counterweight.