Angles and Rectangles of the Balance: Real, Semireal, Potential
The proportion of the arms' angles to their plumb-lines equals that of the opposite weights
This folio classifies the angles and rectangles formed by a balance's arms and its plumb-lines as real, semireal or potential. Leonardo states that the proportion the arm-angles bear to the line of their pendulums is the same the opposite weights bear to one another. Successive beam diagrams are labelled to identify potential angles such as m f h and a n f, and rectangles such as the semireal a b t and the potential a c f. Right angles a c S and a d r are named as potential.
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Arm-angles proportional to the opposite weights
The proportion that the angles formed by the extremities of the balance's arms bear among themselves, together with the line of their plumb-lines, is the same the opposite weights bear among themselves. The rule ties the geometry of the arms directly to the loads they carry.
Potential angles m f h and a n f
The angles m f h and a n f are identified as potential angles. Alongside, n m f is named a potential rectangle and n g b a semireal rectangle.
Semireal and potential rectangles a b t and a c f
The rectangle a b t is semireal, composed of a real cord and the potential lever a b. The rectangle a c f is potential, formed from the cord and from the potential lines c f and f g.
Potential right angles a c S and a d r
In the lowest figure the angles a c S and a d r are named potential right angles, completing the survey of the angle types made by the balance's cords and levers.