Didascalia: Codex Atlanticus, folio 656 a.

Theme investigated on the folio: the weir on the San Marco canal. On the upper part of the folio there is a front view of the corner sluice gate, with the small hatch operated from the tow-path, which allowed to reduce or increase the flow of water in the weir. This device was part of a much larger project which was to connect the Martesana canal to the city's inner waterways by means of the San Marco and Incoronata locks. On the lower part of the folio, there is a plan of the weir and, further down, a cross-section of the same weir, with annotations regarding its construction.