What weight and its centre are; impetus and a clock vane
Weight and its centres, the consuming of impetus in a spun rod, floating elements, and a clock's air-vane
Under the heading 'What weight is and its centre', Leonardo defines weight as a desire of flight arising when one element is carried into another, and states that a heavy body's surface encloses innumerable centres of three kinds. Small diagrams labelled with the elements air, water, earth and fire show bodies floating in layered media, and a note observes that water does not weigh unless a lighter element lies beneath it. Two device studies accompany them: winding a rod a b and releasing it to spin, whose turns die away like a bouncing ball to show how impetus is consumed, and a note that a clock's vane resists the wind less the more arms it has.
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What weight is, and its innumerable centres
Weight is a certain thrusting or desire of flight arising from one element carried into another, whose only end is to flee the place that can neither sustain it nor let it stay, so that it continually pulls or pushes on its support. The surface of every heavy body encloses within itself innumerable centres, which can be judged of only three various natures.
The consuming of impetus in a spun rod
Wind the wood a b many times, let it go in a circle, and count the turns it makes one way and then the other, and the differences of the diminishing. You will see the turns go on consuming, like the bounces of a ball, revealing the manner in which impetus is consumed.
A clock's air-vane and its number of arms
When the vane of the clock has more arms, it resists the wind less, because it finds the road of its motion more continuously open.
Water weighs only over a lighter element
Water does not weigh if it does not have beneath it an element lighter than itself. The accompanying figures label the layered media as air, water, earth and fire, showing bodies floating within them.