Diminution of obliquity: weight and friction
As a slope flattens the weight on its support grows while friction is destroyed
The note observes that as a slope's obliquity diminishes, the weight borne by its upper oblique support increases, while the friction correspondingly decreases, until at the least obliquity the weight is at its greatest and the friction is destroyed. A balance beam and double inclined planes (labelled b a c, n m, S t v, with weights of 4 and 4) show that two weights in the same ratio as the balance arms will not keep that ratio unless the slopes on which they rest are also in the ratio of the weights. Leonardo explains that an oblique weight weighs in two ways at once, toward the centre of the world and along the slope, and that the true natural weight lies between what the right-angled balance bears and what the slope bears. A cross-reference sends the reader three folios ahead.
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Less obliquity, more weight, less friction
As the obliquity diminishes, the weight on its upper oblique support increases, and as the weight increases its friction diminishes, so that at the last diminution of the obliquity the weight is at its greatest and its friction is destroyed.
Two weights keep their ratio only if the slopes match
When two weights hang on opposite arms of the balance, even in the same ratio as the arms that sustain them, they will not keep that ratio unless the obliquities where they rest are also in the ratio of the weights.
An oblique weight weighs in two directions at once
Pendants equidistant from the centre of the rotating body do not always show equal weight, even when the weights are equal, because an oblique weight weighs in two ways: toward the centre of the world and along the slope. The true natural weight lies between what the right-angled balance bears and what the slope bears.