Water Through a Narrowing Channel
Red-chalk study of how a current shifts and rises as it enters a strait
In red chalk, with the notebook turned upside down, Leonardo studies how water speeding from a wide pool into a narrow channel behaves. Keyed to the letters h, g, n, b, a, d, c, o, K, f, e, four numbered observations track how the current first swaps from right to left, then how the mid-channel surface alternates between rising above and sinking below the rest of the water's width along successive stretches. A schematic diagram runs down the left margin beside the text.
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Rise and fall of the mid-channel current
Water descending from a wide pool into a narrow channel shifts from right to left at the entrance (g d, h c). The middle of the channel then rises above the rest of its width (a n b), sinks below it over the next equal stretch (c o d), and rises again further along (e Kf).