Weight on a balance arm swung through a graduated arc
A large protractor-like semicircle over a beam on a fulcrum, with a smaller graduated quadrant and plumb below
A large semicircle divided into graduated degrees, with radii drawn from its centre, stands above a horizontal beam that rests on a fulcrum and carries a suspended weight at one end. At the lower left a smaller quarter-arc bears the same graduation marks and a hanging plumb-line topped by a canopy-like shape. The figures study how a weight's effect changes as its arm rotates through an arc; the long column of Leonardo's mirror-writing on the right is not transcribed here, and the Bibliothèque de l'Institut de France stamp is present.
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Graduated arc measuring an arm's inclination
A semicircle is ruled into graduated divisions and filled with radii from its centre, above a horizontal beam balanced on a fulcrum with a weight hung at one end. The construction measures how the leverage of a weight varies as its arm is raised or lowered through the arc.
Smaller graduated quadrant with plumb-line
Below and to the left a smaller quarter-arc repeats the graduation and carries a hanging plumb-line whose cord rises to a canopy-like shape. It is a compact instrument for reading the angle of a suspended weight.