Proof of the Obliquity of Gun-Embrasures
Splay of loopholes analyzed by triangles and a circle-sector in a square
Leonardo sets out to prove the 'quality of obliquity' of gun-embrasures (balestriere), lettered b - d - a c. He argues that in pyramids of equal base the proportion among the obliquities of the sides equals the proportion of their heights, then demonstrates the point with a figure of triangles and a circle-sector inscribed in a square (n S h - m - o - r - p q). By that construction the embrasure n h is shown to have double the obliquity of the embrasure p q S.
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Obliquity of the gun-embrasures
The note proves the 'quality of obliquity' of these embrasures (balestriere), lettered b - d - a c. In pyramids of equal base, the proportion among the obliquities of the sides equals the proportion of their heights.
Triangles and circle-sector inscribed in a square
A lower figure of triangles and a circle-sector inscribed in a square (n S h - m - o - r - p q) is built to define the figure above. By it the embrasure n h is proven to be of double the obliquity of the embrasure p q S.