Canals for the city drawn from the Ticino
A main canal to divert the whole river, flush the streets and keep cellars dry
The sheet continues Leonardo's scheme of canals for the ideal city, showing a river with a derived, partly underground channel controlled by a lock (conca) and captioned 'method of canals for the city.' He proposes a main canal able to carry the whole Ticino when it runs too high, with the other intakes shut, so it feeds no other channel. A running river is wanted so as not to corrupt the city's air and to flush the streets yearly with rakes when the sustaining weir is lifted; the cellar floors sit three braccia above the canal surface and slope toward the canals so any flood drains away and leaves them clean.
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River, derived channel and lock: 'method of canals for the city'
A river with a derived, partly underground channel is shown running to a lock (conca), captioned 'method of canals for the city.' A gridded plan at the upper right lays out the plot with its canal.
Main canal to carry the whole Ticino in flood
A main canal is sized to take the entire Ticino when it runs too swollen, the other intakes being shut, and it is to empty into no other canal. A running river is wanted so as not to corrupt the city's air.
Yearly flushing and raised, sloping cellars
Once a year the sustaining weir is lifted so the flow, worked with rakes and scrapers, flushes the accumulated mud from the city. The cellar floors sit 3 braccia above the canal surface and slope toward the canals, so any flood drains off and leaves them clean.