On the Motion and Measurement of Water

LEONARDO DA VINCI 275

...and rests with its surface equidistant from the center of the World original: "centro del Mondo"; in Leonardo's cosmology, this refers to the center of the Earth as the center of gravity. This is the source of growth and the vital fluid original: "umore"; referring to the moisture or "humors" essential for life in plants and animals of all living bodies. No sublunary a traditional term for the Earthly realm below the orbit of the moon thing maintains its primary figure and form without it. It binds and increases bodies, and gives them growth. Nothing lighter than water can penetrate it without violence. It readily rises through heat as a thin vapor through the air. Cold freezes it; stillness corrupts it; it takes on every odor, color, and flavor, though by itself it has no flavor, nor color, nor odor. It penetrates all porous bodies. Against its fury, no human defense is of any use, and if it is, it will not be permanent. In its swift course, it becomes a supporter of things heavier than itself. It can, with motion and leaping, lift itself on high. When it falls, it submerges with it, in its ruins, things lighter than itself. It governs its course, sometimes in the middle, sometimes at the bottom, sometimes at the top; one volume of water climbs over the intersecting course of another; and if it were not so, the surface of flowing waters would be without ripples original: "globi"; literally "globes," describing the rounded, mound-like shapes of water in turbulent flow; every small obstacle, whether on the bank or on the bottom, will cause damage to the opposite bank or bottom; shallow water does more damage to the bank in its course than it does when it flows full meaning when the river is at its full capacity, the flow is more stable than when it is low and erratic. Its parts exert no weight upon the parts beneath them, and its upper parts do not press down original: "non danno granella"; likely a transcription error for "gravezza" (heaviness or pressure) on the lower ones.

CHAPTER IV.

Every flexible and liquid element necessarily has a spherical surface, as does the element of water. And this is proven, but first, it is necessary to establish some concepts, which are:
1. That thing is higher which is farther from the center of the World.
2. That thing is lower which is closer to said center.
3. Water does not move by itself unless it descends.
4. In moving, water descends.

These four concepts serve me to prove: that water, which does not move of its own accord, has its surface equidistant from the center of the world—not speaking of droplets, or other small quantities that attract one another like steel attracts its filings an early observation of surface tension compared to magnetism, but of large quantities. I say that no part of the surface of the water moves by itself unless it descends. Therefore, the sphere of water, having no part of its surface that can descend, must—according to the first concept—not move by itself. And if you carefully consider every tiny particle of such a surface, you will find it surrounded by other similar particles, which are at an equal distance from the [center]...