Equidistant centres of weight and the earth's shifting centre
A suspended composite rod, and a remark that the world's centre moves with the tides
A diagram of a composite rod suspended from a horizontal beam (labelled a, n, m) accompanies rules for equilibrium. Leonardo states that if the centres of the weights are equidistant from their common centre they will balance equally, and that the same holds if the perpendiculars of those centres are equidistant from the perpendicular of the common centre, provided the weights themselves are equal. A starred corollary extends the idea to the whole earth: the centre of the world is always in motion because of the changing inundation of the Ocean.
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Equidistant centres balance equally
If the centres of the weights are equidistant from their common centre, the weights stand equal in equilibrium. The same follows when the perpendiculars of those centres are equidistant from the perpendicular of the common centre, so long as the weights are equal.
The centre of the world moves with the tides
Leonardo draws a cosmic consequence from the balance rule: the centre of the world is always in motion. He attributes this shifting to the changing inundation of the Ocean, that is, to the tides redistributing the earth's weight.