Water Screws, a Drawbridge, and a Powder Question
Twin Archimedean screws turning a waterwheel, and Donnino's drawbridge shaft
The upper sketches show two Archimedean water-screws crossed in an 'X', the rising water at the top of one column turning a waterwheel, beside a partitioned rectangular frame whose looping strokes recall an advancing platform bridge seen from below. A short note asks which throws a ball farthest: powder doubled in quantity, in quality, or in fineness. Lower down, a shaft with axial journals lettered a, b, c and d records the drawbridge mechanism that Donnino showed Leonardo, warning that because planks c and d press downward the span a-b twists, and must be reinforced with a thick iron rod wound around the wood.
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Twin water-screws driving a waterwheel
Two Archimedean water screws are set in the form of an 'X'; at the top of one screw column a waterwheel is turned by the water it raises. A partitioned vertical rectangle beside them, with looping vertical strokes, appears to give a schematic underside view of an extending platform bridge.
Which powder shoots farthest
A single question weighs three ways of increasing a charge: powder doubled in quantity, doubled in quality, or doubled in fineness. Leonardo asks which of these throws the ball the greatest distance.
Donnino's drawbridge shaft and its torsion
A horizontal shaft with axial journals carries a short section marked a and b, with planks attached to it extending in opposite directions as c and d. Because c and d thrust downward, the span between a and b is twisted, so Leonardo proposes remedying the torsion with a thick iron rod wound around the wood on the opposite side.