Ciclo CCXC

Illustrissimo Signor mio,

The breach at San Leo is still open on the north face where the rock crumbles like wet chalk. The guns we placed last month fire too high; the parapet absorbs the recoil but the shot strikes the cliff above the road, not the slope where men march. I measured the angle again this morning with the quadrant and the wind from the east shifts the ball two degrees to the left. Correct this by lowering the platform by one braccio and set the trunnions three once forward. The stonecutters can do it in three days if the rain holds off.

The second matter: the powder magazine leaks humidity through the northern wall. The lime plaster you ordered is too thin; the joints between the blocks weep. Scrape the old mortar out to the depth of a palmo and repoint with a mix of one part quicklime to three parts crushed brick dust. Add a coat of boiled linseed on the interior face. The cost is twelve ducats and the work must be done before the autumn mists return.

I enclose a sketch of the new embrasure positions and the mortar mix. The diagrams show the line of fire intersecting the road at 140 passi from the gate, where the earthwork rises. If the gunners hold to the white mark on the timber, the ball will strike the march route before the enemy can form ranks.

Valete.

— L.