Ciclo LXXVI

Illustrissimo Signor mio,

I write from Amboise, where the Loire is wide and slow and the king’s court asks me to paint ceilings. But my mind is still on the walls we walked together, and so I set down what I have not yet delivered.

The rampart at Cesena — the eastern face — the slope is wrong. I measured it again from my notes. The talus is too steep at the base; a battering ram brought to that angle would find purchase where it should not. The earth behind the revetment is not compacted in layers of the thickness I specified. If your masons followed the drawing I left, the wall will stand one season of siege. If they did not, it will not stand two. I say this not to reproach but because the matter is what works.

The canal at Imola — I have reconsidered the dam. The site I marked on the map, two hundred paces south of the gate, where the bed narrows between the two limestone shelves — that is still the place. But the sluice must be of oak, not pine. Pine rots in standing water within three years. Oak, if the joints are caulked with pitch and horsehair, will hold a decade. The cost difference is twelve ducats. I have written the specification on the sheet enclosed.

Artillery placement on the northern approach — the two culverins I positioned on the covered way cover the road from Forlì as I said they would. But the embrasures are cut too wide. A bombardier standing behind the left gun can see the road; a marksman on the road can see the bombardier. Narrow the opening to the width of a man’s shoulders. The gun still fires. The man is no longer a target.

I do not know if you still hold these towns. I do not know if the maps I drew are in a chest in Rome or burned. I write as one engineer to another sovereign, and the sovereign may be dead, and the engineer’s hand may shake, and the page receives what the mouth cannot say to a man who may no longer hear it.

The candle is low. The canal again tomorrow.

Di Vostra Illustrissima Signoria, Leonardo