On Weights: Beginning of This Book
Equal weights on inclined planes and cords over pulleys
Headed 'De pesi. Principio di questo libro' (On weights. Beginning of this book), this page opens a treatise on weights with numbered propositions and several apparatus sketches: a pulley with two weights on inclined planes, a companion figure, and three pulleys with variously angled cords. Leonardo sets out four cases relating weights, arms and obliquity, holding that equal weights maintain equal gravity in equal obliquity. A final proposition states that a cord passing over a pulley, windlass or other round instrument always meets the opposite faces of its semidiameters at right angles, whatever the obliquity of the cords.
On this page
Equal weights keep equal gravity at equal obliquity
If weights, arms and motions are equal in obliquity, the weights will not move one another. Equal weights maintain equal gravity in equal obliquity; if equal weights in equal obliquities do move one another, the arms of the balance are unequal.
Four cases of weights, arms and obliquity
The four numbered cases show when equal weights and arms yield equal or unequal effects: weights prove unequal when their appendicles have unequal obliquities, and equal weights on equal arms that move one another do so with motions of unequal obliquity.
A cord over a pulley meets its radii at right angles
The cord hanging from the opposite sides of a pulley, beam, windlass or other round instrument always divides or joins at right angles to the opposite faces of that instrument's semidiameters, whatever the obliquity of the cords.
Pulley and weights over inclined planes
The figures show a pulley carrying two weights set on two inclined planes, and a further pulley with two weights resting on an inclined plane, illustrating the statics of loads balanced over a wheel. A marginal label marks the 'second' figure.