Heaviness along a cord and weights ranged on a semicircular arc
Weights ranged on an arc about d, and two balances testing how a hung weight acts along its whole cord.
Folio 40v gathers three balance studies. In the first, a weight tied to d is shown at several positions on a semicircular arc, with dotted plumb-lines dropped to the diameter through the points a, f, d and v (weights m and n) so that the horizontal offset of each position can be compared. A short note headed 'Conception' states that the heaviness carried by a cord acts along the cord's whole length and is entire at every part of it. Two further balance staffs — one hanging equal weights from the midpoints of its arms, the other unequal weights on unequal cords — illustrate the same principle.
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A weight is carried at every point of its cord
In a note headed 'Conception', Leonardo states that the heaviness suspended by a cord is present along the whole length of that cord and is entire in every part of it. The balance drawn beside it hangs equal weights from the midpoints of its two arms to make the point.
A weight ranged on the arc about d
A weight fastened at d is drawn at several positions along a semicircular arc, some shown with the cord and some without. Dotted vertical lines fall from each weight to the horizontal line through d, meeting it at a, f, d and v, with weights labelled m and n, so their horizontal distances can be compared.
Unequal weights on unequal cords
The lowest drawing is a balance staff hanging a spherical weight from each end, the two weights differing in size and the cords in length. It poses how such a beam settles when both the loads and their suspensions are unequal.