River Fords, Flood Deposits, and a Membrane Vane
Where rivers may be crossed safely, gravel and sand banks, with a red-chalk vane device
The upper fragment (70a) explains, with lettered points, where rivers can be forded outside the flood zones, how moderate floods pass through the bends of a river, and how the banks carry coarse gravel at one place and fine earth-mixed material at another, with the current marked at g and a width given as two braccia. The lower fragment (70b) shows a large membrane-and-ribs vane and linked mechanism drawn in red chalk, annotated with a component a that 'holds the hand' and dimensions in braccia for a leather ('corame') element. In the Codex Atlanticus the leaf is catalogued under rotating blades for the defence of walls. Faint red-chalk marks beyond the transcribed labels remain on both sheets.
On this page
Where rivers may be forded and how floods lay down gravel (a, b, g)
At a b one fords the rivers outside the floods, which then fill from n m and o p; r S and t v are where moderate floods pass in the many windings of rivers. On the covered banks the gravel is coarse and unmixed at t b, fine and mixed with earth at v p, while o g marks the current.
Device component a and its leather part in braccia
A drawing at the right is marked a, noted as the part that 'will hold the hand'. A lower-left drawing gives a leather ('corame') element with dimensions of 2 and 11, and 2 and 9 braccia.
Large membrane-and-ribs vane (red chalk)
A broad ribbed membrane fanning from a hub, linked to a mechanism, dominates the lower sheet. The Codex Atlanticus catalogue assigns this leaf to the theme of rotating blades for the defence of walls.