Free fall to the world's centre and the flow of falling water

Heavy bodies fall toward the centre of the world

Every free descent of a heavy body is directed toward the centre of the world, provided the motions are equally swift. A companion note observes that of bodies released in sequence the one that departs first ends lowest and the last highest, the middle one threaded by the line joining the outer two.

No instant of rest in any motion

Because the instant of motion is indivisible while its time is divisible, no motion however slow contains any smallest part of time in which it could come to rest. With a b equal to a c, the line d e f bisects each side of the triangle and g h i cuts each side at its quarter; when the mover and the first moving body start at right angles, the positions of all the rest fall on the straight line r f g.

A stream of falling water keeps constant volume

Leonardo argues against an adversary that falling water never thins or loses quantity along its descent, so equal weights pass every cross-section in equal time. Were more water to enter a place than leaves it, all the water in the world would in time pile up there, as two casks entering against one poured out would accumulate without end.

Transverse and natural motion of scattered sand

A falling stream of evenly scattered sand illustrates compounded motion: the transverse motion is to the natural downward motion as the side a b is to the side a g. If the mover runs faster than the sand falls, its horizontal path exceeds the fall in the same proportion, measured in equal time.

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Quel che prima si partì1, si truova più basso, e quel che fu ultimo sarà più alto, e quel di mezo sarà infilato dalla linia che infila il primo e l'ultimo. Adunque ...

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That which departed first is found lower, and that which was last will be higher, and the one in the middle will be threaded by the line that threads the first and the last. Therefore ...

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