Dragging a weight of 12 with friction; the lever rule continued
Friction taken as one third of the load; arms n p, n o, n m and the pulling line S o
This recto extends the lever rule and then treats friction. Leonardo compares the present figure to the previous one, noting that the arms n p, n o and n m stand in triple, double and equal ratio, so that a pull along b a resists 4 at p. He then poses the problem of dragging a heavy body (weight 12) along its base, taking the friction on the contacts as always one third of the weight of the dragged body, hence 4 of resistance. Pulling the cord along the line S o balances the motion, since lever o c equals contra-lever c d, but because the moving power is always greater than the thing moved, the true dragging happens between o and c.
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Arms n p, n o, n m in triple, double and equal ratio
Because line a n is quadruple to line n p (the arms of the balance whose pole is corner n), one who pulls along line b a resists 4 at p. And because n p, n o and n m are triple, double and equal to one another, they operate with the interchangeable proportions of weights. Pulled upward, this body cannot withstand more resistance than its own weight.
Friction as one third of the load in dragging
To drag the weight a b c e (12) so that its base has even contact with its plane, the friction on the contacts is always one third of the weight, hence 4 of resistance. Pulling along line S o causes common motion, since lever o c equals contra-lever c d; but because the moving power is always greater, the true dragging falls between o and c.
Rectangle with fan of lines and a swept arc
The upper figure is a rectangle with lines radiating from a corner out to a vertex at the right and a curved arc struck through them; the lower figure sets a small rectangle against a row of parallel horizontal lines labelled q, p, r, o, s. These carry the geometric measure of the lever arms.