The citadel tower and moat: dimensions and cost
A full page costing the round citadel tower, its spiral stair, the ravelin ditch walls, the town parapet and the moat
This verso is a densely written page of military-engineering estimates. Leonardo sizes the round citadel tower (25 braccia in diameter, 78 4/7 in circumference, 20 high) at 585 canne or ducats, then deducts the incorporated corner wall and a spiral staircase to reach a net 329 ducats, noting the artillery platform at its summit. He goes on to cost the ditch walls aligned with the ravelin at 343 3/4 ducats, the town parapet at 562 1/2 ducats, and the dimensions of the moat, the account explicitly continuing onto the facing recto. Two small pen sketches at the right show a toothed wheel and an L-shaped bracket.
On this page
The citadel tower: dimensions, spiral stair and cost
The round citadel tower, 25 braccia in diameter, 78 4/7 in circumference and 20 high, gives 9360 square braccia, which divided by 16 make 585 canne, so 585 ducats with all the master's expense. From this he subtracts the 156 4/16 canne of the corner wall incorporated into it and 20 canne for a spiral staircase, leaving 329 canne, or 329 ducats, and notes the artillery platform at the summit.
The ravelin ditch walls, the town parapet and the moat
The ditch walls that align with the ravelin, 10 braccia high and one thick, run 300 braccia toward the town and 250 along the bank (550 in all, 343 3/4 ducats). Above them the town parapet, 6 thick, 5 high and 300 long, comes to 562 1/2 ducats. The moat is measured at 275 braccia long, 21 wide and 10 deep, the reckoning breaking off to continue on the recto.
Converting braccia to canne and ducats
Throughout, Leonardo multiplies the linear dimensions to get square braccia, divides by the wall-canna of 16 braccia to obtain canne, and prices each canna at one ducat, so that the geometry of each element is turned directly into a money figure.
