A water pump, a locked handle, and three maxims
Pump studies and counterweights; a key-locked device; maxims on trees, walls and the divided mind
The right-hand page (f.177r) studies a water-lifting pump ('tromba'): Leonardo asks what the water inside it weighs, insists that its counterweights be balanced only when the tube is full, and warns that the pump's mouth must clear quickly so the water does not fall back down. The left-hand page (f.180v) carries three red-chalk maxims, that a tree's inner branches wither in excess shade while only its outer ramifications survive, that a wall breaks only over something lighter than itself, and that a mind divided among many studies, like a divided kingdom, is confounded and weakened, together with a small device whose handle, he notes, should be locked with a key. The pump is drawn with lettered figures (a, b) whose diagrams are not transcribed in the source.
On this page
Why a tree's inner branches wither
All the little branches born toward the middle of the tree dry up and fall through excessive shade, and only those ramifications keep themselves which are at the outermost parts of the tree.
A kingdom, and a mind, divided
Just as every kingdom divided in itself is destroyed, so every mind divided among various studies is confounded and weakened. Beside it stands a companion maxim: a wall does not break unless it has beneath it something lighter than itself.
A handle locked with a key
Beside a small mechanism in the lower half of f.180v Leonardo notes that the handle should be locked with a key, adding the single word 'Good'.
The mouth of the pump must clear at once
The mouth of the pump ('tromba') must clear itself immediately, so that the water does not fall back down through the tube.
The weight of water in the pump
What weight has the water in the pump? a b lifts. The counterweights must be equal when the pump is full of water, not when it is empty, for when empty it only stays raised. Only that water weighs which is outside its sphere.