Water Flowing Between Two Tanks
Height above the opening set by the width of the outlet, in proportion
In red chalk Leonardo compares two tanks (bottini), one pouring into the other. He states that the water which discharges through the narrower opening stands higher above its opening, and that the ratio of those heights matches the ratio of the widths of the openings. A schematic sketch at the top shows two upright posts or gates linked by horizontal water-level lines.
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Height inversely tied to the width of the opening
Of the waters one tank pours into another, the flow through the opening of lesser width stands higher above its opening, and the proportion of that height equals the proportion of the widths of the two openings.