The Pressure of Liquids: Vats and a Well with a Skin Bag
Where a liquid pushes hardest, and a paradox of weight in a well
Two hydrostatic problems share the sheet. Above, two broad vats—one lying on its side, one raised on supports—each send out a stream of water to illustrate the rule that a movable liquid presses hardest against the part of its container wall farthest from the center of its surface. Below and at the right, a cross-section of a well holds a skin bag beneath a great weight of water, prompting Leonardo to ask what supports the skin and whether it bears or relieves the water's weight.
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Where a liquid presses hardest against its vessel
Every movable liquid body strives and pushes more against the part of its enclosing wall that is most distant from the center of its surface than against any other part of the vessel. The two spouting vats give the rule visible form.
The well and the skin bag: a puzzle of weight
A well holds at its bottom a skin bag so large that only a finger's thickness of water lies below and around it, so that the water below weighs a hundred pounds and that above the skin ten thousand. Leonardo asks: why does the skin not burst, what supports it, and does the skin bear the water's weight or remove it?