Bridges of Borgo Ognissanti; river silting and mountain winds
A Florentine bridge survey, a lettered study of deposited sand and silt, and how wind bends through valleys
Folio 273v gathers survey work and water studies: measurements of the bridges near Borgo Ognissanti in Florence (widths, embankments, piers and pillars in braccia), a note that the wall of Le Casace aligns with the gate of San Niccolò, and a lettered diagram showing how flood water striking at n forms a covered island and lays sand and silt across b d and n d f. Folio 276r is a dense essay on the movement of air: how winds change course through the mouths of valleys, empty out like water through conduits, and condense and rise against mountain summits before curving away. Numerous diagrams and further untranscribed notes fill the left leaf.
On this page
Where flood water strikes, an island of sand and silt forms
In a lettered channel diagram, when a b and c b prevail the water strikes at n and forms a covered island over the whole of b d, laying sand and silt in n d f; at low water only a b e prevails, the flow cannot pass the silt already deposited, and the stream b d breaks at d and then at r.
How winds turn through valley mouths and rise on mountains
The course of the winds changes through the mouths of valleys, emptying like water poured from a cistern through several conduits, most along the line of entry; and wind condenses over the places it strikes, gathering on mountain summits and rising in straight lines before curving away.
An alignment note across the city
An inverted note records that the wall of Le Casace aligns with the gate of San Niccolò, fixing a sightline across Florence.
Measured spans of the bridges at Borgo Ognissanti
A survey lists bridge dimensions in braccia at Borgo Ognissanti in Florence — widths, embankments, piers and numbers of pillars — including a bridge 152 braccia long.