Transverse motion of a weight; lifting a long load by its centre
Why accidental motion barely loads the perpendicular; equilibrium of bases and pyramids
Leonardo argues that a weight n set in transverse ('accidental') motion gives little or no load to its perpendicular, so the end a of the balance scarcely feels it - the weight leaving g would go toward m but is forced to arrive at n. A second rule holds that any long weight lifted by one end must be raised along the central line of its length, the cord passing over the centre, as shown by n m. A closing note asks the reader to compare the proportions of the weights o b f and K o a f with their bases and 'pyramids,' equilibrium following when the bases match their sides. A perspective sketch of a lifting frame and a bowl are drawn in the margins.
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Transverse motion barely loads the perpendicular
A weight n moving transversely gives little or nothing of its weight to its perpendicular, so the balance end a scarcely feels it; the weight leaving g would go to m but is forced to reach n, and burdens only by its accidental motion. Load is felt in the direction of the motion, not along the vertical.
Lift a long weight along its central line
Any long weight to be raised by one of its ends must be lifted along the central line of its weight, that is, the lifting cord must pass over the centre of its length, as n m stand below. Lifting off-centre would tip the load.
Proportions of weights, bases and pyramids
Leonardo asks the reader to measure how the weight o b f relates to K o a f, and how the bases a n, r b and f m relate to their pyramids; when the bases are similar to their sides the weight stands in equilibrium, as shown in y t p. The rule ties equilibrium to the geometry of the supporting figures.
Perspective sketch of a lifting frame
At the upper left a beam and frame are drawn in perspective with cords and pulleys, the apparatus that carries the long weight discussed in the text. A bowl with radiating lines is sketched at the lower left.