Dividing a circle into equal parts; a crossbow and composite beams
A single compass opening yields 3, 5, 6 and 30 divisions; below, a large crossbow and screw-bound beams.
The top of the sheet works out how to divide a circle into several equal parts using a single opening of the compasses, with a labelled circle inscribed with intersecting arcs and chords. A faint group of male figures, one holding a weapon, is sketched at the upper right. Below, Leonardo draws a large crossbow and structures of composite timber beams, the second of which is bound tight with screws.
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Dividing a circle into 5, 3 and 30 parts with one compass opening
Placing the compass point at a and drawing the chord b c, then from c drawing a d, then a line from b to the intersection n, gives at m the finished measure: a m is a fifth of the circle, a c a sixth, c m a thirtieth, and a d a third. Leonardo reasons that dividing the circle into 30 parts, a c holds 5 (a sixth of 30), a m holds 6 (a fifth), a d holds 10 (a third), and c m holds one.
The divisions a single compass step marks off
A short note records that with one opening of the compasses the circle is divided at 3 (a d), 5 (a m), 6 (a c), 30 (c m), 22 (n s) and 2 (b d).
Large crossbow (balestra)
A large crossbow is drawn low on the sheet, its bow spanning a heavy stock. The caption names it as a figure of a crossbow.
Composite beams tightened with screws
Beside the crossbow are figures of composite (built-up) timber beams, the second of which is drawn tightened together with screws.
Group of male figures, partly faded
At the upper right stands a lightly drawn male figure holding a weapon, beside a further group of male figures now largely faded or erased.