Digging a ditch: pyramidal gangs and an excavator
The men must always double in number; a bucket excavator is sketched above
The verso continues the excavation study, insisting the gang of diggers form a pyramid widening toward the spoil-heap so the trench floor sinks with an even, level surface. One scheme spreads 106 men across a wide ditch, from a single braccio at the point a to fourteen at the far end b c. Leonardo notes that set singly the men leave the cut square, so they must dig lengthwise and always be doubled, a rule echoed by a marginal doubling series from 4096 down to 1. At upper centre a bucket-bearing excavating machine is sketched.
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The gang of diggers must form a pyramid toward the spoil
The number of men digging a ditch must be pyramidal, with the base of the pyramid set toward the place where the spoil is heaped; otherwise the floor does not descend with an even level surface. Where one braccio of width is dug at a, fourteen are dug at the far end b c, so the cut widens pyramid-fashion, and a wide ditch here calls for 106 men.
Walking backward, and always doubling the men
Set one by one, the men leave the ditch cut square, so instead they must stand in a line and dig lengthwise, first opening a trench, and the men must always be doubled. Walking backward along the ditch, each retreats by the thickness of earth he removes; the man at a must lift ten shovelfuls for every one lifted at b.
An excavating machine with a digging bucket
At the upper centre a mechanical device is sketched, catalogued among Leonardo's excavator studies with a digging bucket. It sits amid the diagrams working out how the human gangs should be arranged.
A doubling series in the left margin
A marginal column steps through a doubling and halving series, 4096, 2048, 1024, 512 down to 1, beside a count of men reaching 150 and 106. It quantifies the rule that the diggers must always be doubled.