Diverting the Arno: floods, channels and the Bisarno cut
Lettered sketches (q, b, c, g, n and p, r) on leading the river through a straighter course
The upper right of the sheet carries small lettered sketches of the Arno's course, with a second sketch at the left lettered p, r; the lower two thirds of the leaf are blank. The notes argue that floods are carried off not by their volume but by the river's falling, weigh the relative force of two reaches (ab against bc), and propose making the Arno run through a straighter channel from n q into g. A further note observes that the river's many bends slow its flow and raise its bed until the water overtops its banks and spawns new rivers such as the Bisarno, and advises cutting a channel to reclaim land beyond it.
On this page
Floods, the force of two reaches, and a straighter course for the Arno
Leonardo reasons that it is not the floods themselves but their diminishing that carries them away, and compares the power of one reach ab against another bc. He concludes that the Arno should be led by way of n q so as to come to g, noting that b c is entirely hollow underneath.
The rebounding jet at h and x
A short adjacent note on the behaviour of the diverted water: if q leaps up to h, h rebounds to x and fills g, and the current will always break at x.
The Arno's bends, the Bisarno, and reclaiming land
The many turns of the Arno slow its course and raise its bed so that the waters no longer stay within the banks but overflow and make new rivers, of which the Bisarno is readying itself to be one by way of p r. Leonardo advises cutting this channel, which will give back land on the far side. A note marks a broken bracket at p.