Index for a treatise on rivers, with a wing and calculations
A rule-of-three sum and a feathered wing beside a planned book of water
The right leaf carries a list of chapter headings for a projected treatise on water: levelling, diverting, straightening, dividing and deepening rivers, and the varied motions of their currents, introduced by the remark that water begins its motion by a degree of obliquity. The left leaf opens with a rule-of-three calculation (12 of turning to 20 square braccia, hence 10 to 16 2/3). Around these run untranscribed sketches: a large feathered wing, radiating star and compass figures, interlaced knot panels, a fluted column, and columns of arithmetic. Only the two blocks transcribed here are translated.
On this page
Chapter list for a treatise on water and rivers
A column of headings, each opened with 'Book', lays out a planned treatise on water: levelling waters, diverting and straightening harmful rivers, dividing them into fordable branches, deepening their beds, and the varied motions of currents through channels and pools. It opens with the note that water gives beginning to its motion by a degree of obliquity.
A rule-of-three calculation
A worked proportion: if 12 of turning gives 20 square braccia, then 10 gives 16 and 2/3, which added to 20 makes 36 and 2/3 braccia. Columns of further figures and fractions are worked across the lower sheet.
Study of a bird's wing
A large, carefully feathered wing is drawn at the upper left, the kind of study Leonardo made of the structure of wings and their action on the air. No transcribed text accompanies it.
Interlaced knot patterns
Panels of woven interlace and knotwork are drawn along the lower center of the sheet, decorative designs of the sort Leonardo repeatedly explored. They carry no transcribed caption.